Difference between revisions of "Common plugs and connectors"

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* http://en.wikipedia.org/wiki/Fast_Ethernet#100BASE-TX
* http://en.wikipedia.org/wiki/Fast_Ethernet#100BASE-TX
* [[Network wiring notes]]
=Video cables/plugs=
=Video cables/plugs=

Revision as of 23:00, 25 April 2022

Yes, this is biased to the stuff I deal with. Ideally 'common' is true enough. Suggestions are welcome.


Mixed use (analog, digital, home electronics, audio)

TRS (Tip, Ring, Sleeve) and variations

3.5mm (1/8") TRS plug (bottom left),
2.5mm TRS plug (top)
6.35mm TRS plug (right)
3.5mm TRRS plug

The history of plugs like these is complex[1], and there are some leftovers today that use less usual variants.

But what you're most likely to meet is primarily:

The 1/4", which is precisely 6.35mm
originates from the design of the first telephone exchanges(verify).
These days they are mostly seen in audio use; see also below.
used for guitars, pro line level (balanced or not), and sometimes for consumer headphones
Americans refer to it as 1/8" (0.125") though it's more like 0.138"
probably the most common of the est
best known for TRS in headphones for stereo sound for a few dozen years, and often referred to as audio jack, mini-jack, jack plug, stereo plug, and others. Sometimes phone connector but that suggests the 1/4" one
often carries consumer line level audio signals, or consumer microphone level
also TRRS for mic-and-headphones on smart phones (and a few other uses)
Americans refer to it as 3/32" (0.09375") though it's more like 0.098"

The 1/4 size is standardized by an inch size because of its phone network origins(verify),

...while 2.5mm and 3.5mm are standardized by millimeters, so the inches are approximations there. (it seems they're always manufactured to mm sizes, so the inch figures are just names)

See also [2]


  • the sleeve is usually ground
  • 3.5mm TRS for sound
tip: left
ring: right
sleeve: ground
  • 6.35mm TRS
sturdier variant of 3.5mm, same level and pinout
balanced audio (pro audio)
some variants around mixers (pro audio)
  • TRRS for headphone, mic and/or buttons [[3]]
Android / the general standard: Left Right Mic Ground (OMTP)
Apple being different: Left Right Ground Mic (CTIA)
  • TRRS - audio and analog video, such as
iPod's AV cable (Left Right Ground Video)
raspberry pi audio+video (same pinout)
there are variants of this. It's handy to have adapters with RCA, in that sometimes you can get around variations by plugging things differently

See also:

Headphone buttons

The buttons will be different resistor values between mic and ground pins.

For Android[4]:

  0..70  ohm   Function A, play/pause/takecall
110..180 ohm   Function D, typically voice commands
210..290 ohm   Function B, volume up
360..680 ohm   Function C, volume down

(The impedance of the microphone itself is considerably higher, and sense-wise acts as the default)

For Apple,

~0   ohm is play/pause/takecall

Other things seem to be proprietary signaling, which allows them to add functionality over time. And piss of imitators and DIYers.


RCA socket and plug
Bunch of RCA sockets (for two types of audio output and two types of video output)

Used for audio, video (often composite, now also component), some simple data (like non-optical digital audio)

Named for its introduction by the Radio Corporation of America.

Other names include cinch connector, phono connector, and some odd ones out like the Dutch calling it a tulpstekker (after tulips, because of course).

See also:


Left: the 180-degrees 5-pin DIN.
Right: 4-pin mini-DIN (here on an S-Video adapter cable)

DIN refers to a whole standardization body.

"DIN connectors" typically refers to members of a specific series of circular plug/sockets, that have a 13.2mm-diameter round metal friction locking shield.

These include:

DIN 41524: 3-pin, 90°, 180°      4-pin, 72°, 216°       DIN 41524 / IEC/DIN EN 60130-9: 5-pin, 45°, 180° 5-pin, 90°, cube, 270° DIN 45322: 5-pin, 60°, 240°       DIN 45522: 6-pin, 60°, 240°       DIN 45329 / IEC 10: 7-pin, 45°, 270°       DIN 45326 / IEC/DIN EN 60130-9: 8-pin, 45°, 270° 8-pin, 45°/41°, 262°

These come from at least five different DIN standards.

It seems the original DIN standards are out of print, and you now want to read IEC 60130-9, which also expanded the series (verify))

It seems to help that it was a existing, relatively sturdy, relatively versatile, and relatively cheap style of connector.

The plugs were once more common, with uses like digital (e.g. MIDI, AT keyboard connector), audio/video (e.g. tape decks, microphones), and sometimes power.

Many of them were fairly specific to brands or devices (e.g. Commodore 64 uses 7-pin for power, and 8-pin (5-pin in a few early models) for audio and compositite video).

Of those, only MIDI is something still built into devices.

Many such uses have since grown more specific connectors. Which is probably good, to avoid smoky mistakes from too many distinct uses sharing a plug.

Also relevant:

  • DIN 41529: 2-pin, historically seen in loudspeakers, though I've also seen them used for low voltage lighting
    Speaker din male and female.jpg

See also:

Look a bit like


Mini-DIN is a similar-looking variation also from DIN, with a 9.5mm round metal shield. Additionally uses plastic slots that makes plugging into other variants hard without a hammer.

These include: MiniDIN-3 Diagram.png MiniDIN-4 Diagram.png MiniDIN-5 Diagram.png MiniDIN-6 Diagram.png MiniDIN-7 Diagram.png MiniDIN-8 Diagram.png MiniDIN-9 Diagram.png

Probably best known for

PS/2 keyboard/mouse (6-pin)
S-video (4-pin)

Other uses include audio, video, some communication, and some fairly one-off video card adapters back when analog video was still a thing we wanted.

Also applied in a number of proprietary uses - though those often see non-standard variants (see below).

See also:

Mini-DIN lookalikes

Not a standard 7-pin mini-DIN plug. This one is used on a video card that had analog outputs

There are a number of have the same 9.5mm housing as mini-DIN, but are not standardized or approved by DIN.

These include: Pseudo miniDIN-7 Diagram.png Pseudo miniDIN-8 Diagram.png Pseudo miniDIN-8b Diagram.png Pseudo miniDIN-9 Diagram.png Pseudo miniDIN-9b Diagram.png Pseudo miniDIN-10 Diagram.png Pseudo miniDIN-10b Diagram.png

Some are designed to be compatible with specific standard mini-DIN (e.g. to have a video card socket that accepts both standard S-Video plug but also its own connects-more-stuff variant).

Others are designed to be specifically incompatible with any standard mini-DIN (most, I think?).

Modular connector (?P?C); Registered Jack

8P8C plug, 6P6C plug, 6P4C plug, 4P4C plug, 6P6C socket

Modular connector (when it refers to a specific connector) were developed for phone uses but got used more widely.

Variations of socket and plug are named by

  • how many positions there are (which also implies the plug/socket width), and
  • how many conductors are actually present (filled out from the center positions).

For example, 6P2C has 6 positions and two conductors, 8P8C has 8 positions and has conductors in all positions.

The 2, 4, 6, 8 positions/lead connectors are mostly standard, 10P10C and further variations also exist.

Smaller plugs fit in larger sockets, e.g. 4P and 6P plugs fit in 8P sockets, and only in one position because the clip centers the plug.

Within some specific uses, this is intentionally designed for this to be useful and safe. In other cases, and more creative use, this doesn't help anything.

RJ meaning analog phone

Registered Jack refers to a handful of analog telephone wiring standards, most of them on these modular connectors (exceptions include the RJ21 centronics style connector, and some adapters).

There is some correlation/association between specific connectors and likely uses (in specific contexts). Consider for example

  • 4P4C ~ RJ9 (mostly used to connect handsets to phones - two pairs, one for the microphone and one for the speaker)
  • 6P2C ~ RJ11 (one-pair, one telephone line)
  • 6P4C ~ RJ14 (two-pair, two telephone lines)
  • 6P6C ~ RJ25 (three-pair, three telephone lines)
  • 8P8C ~ RJ45 (sort of), and RJ49 (ISDN)(verify)

(For larger lists, see e.g. [Wikipedia: Registered_jack#List_of_official_types] ):

RJ45 meaning ethernet?

Technically, RJ45 refers to phone wiring (on 8P2C(verify)), and is almost completely unrelated to Ethernet.

Practically, within the computer world RJ45 refers to 8P8C connectors wired for Ethernet, to the point that it's actually hard to do a web search for the original phone wiring.

A further reason for confusion is that for a time, you could use the same wiring, and even the same 8C8C socket socket, to do a single analog phone line, and 100MBit Ethernet, because

6P2C plugs into 8P8C sockets fine and would use the center two pins
100BASE-TX (and 10BASE-TX) would use four of the other pins
Ethernet cables of the time typically wired all four pairs anyway (of which two were rarely used)

This was never ideal in that it could lead to some pricy mistakes, and now less common as there is no such free pair in the now-standard 1000BASE-T, and office phones are now often VoIP anyway.

Less standard ?P?C uses


See also:

Video cables/plugs

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Composite video

Female and male RCA. Yellow is associated with video use (much like red and black (or red and white) are with stereo sound)

Composite video (not to be confused with component video)

Usually plugs around in a one-yellow-RCA-plug way, sometimes using a BNC plug.

Carries Y, U, and V with sync pulses, and is also easy to broadcast - it is almost entirely the same as analog TV's format. Video recorders and some early computers modulate such a signal onto a local video channel, on their antenna output wire.

The main upsides to composite is probably that it is easy to transfer video between devices with a simple, common plug.

The main downside is that it susceptible to various visual artifacts, including noise/interference, dot crawl, also depending on the quality of the encoding/decoding hardware.

Quality you get from composite video varies noticeably between different (types/qualities/designs of) devices, and you want to use only shortish cables.

Composite video can also be called CVBS, an acronym with various possible readings, depending on who you ask: "Color, Video, Blank and Sync", "Composite Video Baseband Signal", "Composite Video Burst Signal", or "Composite Video with Burst and Sync".

Component video (YPbPr)

Red, Green, Blue RCA (...which suggests component video)

Component video (not to be confused with composite video) could refer refer to any system that sends video in multiple separated channels, but specifically carries a YPbPr signal.

Typically on three RCA connectors, and for YPbPr these connectors are frequently red, green, and blue. (Green plug carries the Y signal (Luma), the blue the Pb (blue minus yellow), and the red the Pr (red minus yellow) signal)

...not to be confused with RGB video, which also exists, in multiple forms (and can be called component video in the wider sense)

See also Color_notes_-_color_spaces#YCbCr_and_YPbPr


S-video plug, the wire carrying two pairs

S-Video (also Super Video or Separated Video, and also sometimes called Y/C) carries luma (Y) and chroma (C) signals on separate wire pairs, using standard 4-pin mini-DIN plugs.

It is similar to composite video in that it carries the same information, but avoids shoving the Y and C information together to be separated later with possibly cheap electronics, which can lead to lower quality video. Still, in fairly ideal conditions (for composite), S-Video is no better than composite.

S-Video-to-Composite-video converter cables can just join the wires (although this may mean the colors are less saturated - something about the voltage amplitudes of these two signals?(verify)).

Note that you can not use that same converter to go from composite to S-Video, as that would put a mixed Y+C channel on both the Y and C pairs. The S-video decoder hardware will usually partially understand this, which results in a black and white image(verify).


Not a standard 7-pin mini-DIN plug. This one is one end of a computer video card adapter cable

You may find video-related cables that resemble the 4-pin mini-DIN S-Video plug. This includes:

  • a 9-pin variation called VIVO (Video In Video Out), seen on video cards, that allows S-Video in, S-Video out, component out, and composite out.
  • I've seen some video cards come with a 7-pin plug. This is rarely a standard mini-DIN plug, and often has its plastic slot in the same place as on the 4-pin DIN plug, but wider, so that the video card socket will accept a standard S-Video plug, and also the plug on the cable supplied with the card which uses the extra pins to carry, usually, another type of video (often composite video, sometimes composite video).
  • a different 7-pin connector (standard mini-DIN) used on some professional (VCR) kits


Plug from a general purpose SCART interconnector cable
Two specific-purpose SCART plugs, with only the pins they need for audio and composite video in a specific direction

SCART (a.k.a. Euro AV, EIA Multiport) combines a bunch of analog audio and video formats used by various common plugs, making it somewhat easier to connect various common home devices.

Before HDMI, SCART was very common on VCRs, TVs, and also frequently seen on DVD players and such.

SCART can carry:

  • Mono/Stereo Audio, both ways
  • Composite video, both ways
  • S-Video may be supported both ways, but isn't always implemented
  • RGB (on newer hardware, by re-purposing some wires, so both ends need to support and both to specifically this (ab)use)
Back of a SCART converter to composite and S-video, and RCA audio. The switch on top lets it act as input or output for each of these

You can easily find adapters to one or more specific things, like RCA audio, composite video and/or and S-Video, and sometimes versions with a switch that selects whether you want to use the converter plug to act as input or output.

RGB is higher quality, but

  • has to be supported by both sides
  • can also not be used at the same time as S-Video output
  • is only meant for player-to-display travel.

Supported primarily by some more modern TV sets (receiving role) and recent media players (sending role) although supporting players only use RGB when you explicitly configure them for it, for compatibility reasons.

See also:


DE-15, also named HD-15 (and also, somewhat incorrectly, DB15 and HDDB15), used for VGA monitor connections

VGA can refer to an old video card that set a graphics standard, but later it mainly referred to the standard connector it uses, DE-15.

VGA made sense when monitors were CRTs and their scanning beam made them all-analog in nature. You had to convert it to analog somewhere, and they chose to do it in the graphics card.

On flatscreens, though, we have discrete pixels, meaning that now we had a digital image in the PC that we send in analog and then convert back to digital to put on those pixels. This is a weird situation and asking for signal losses. Which is why we moved on to digital communication for our monitors.

The 15-pin connector only really has five important signals:

  • hsync, vsync
  • red, green, and blue pixel data

There's a bunch of ground pins, to give each signal its own ground ('return') and allowing twisted pair setups for lower interference(verify).

Four pins were reserved for DDC (Display Data Channel) to help PCs identify monitor capabilities.

which saw a few schemes and protocols over time (including pulldown resistors, one-directional serial, I2C).

One pin is 5V to power the EEPROM used in some of these schemes, but is otherwise unused.

See also VGA hacking


D-terminal plug

D-Terminal (not to be confused with D-Subminiature a.k.a. D-Sub) is probably most common in Japan, and seen elsewhere mostly in specific applications, e.g. digital satellite tuners.

The wires carry component video, and signal lines that use logic-level voltages to signal the video's resolution, ratio, and whether it is interlace/progressive.

Can carry analog 480i through 1080p, varying with the actual devices

Breakout cables to component video over RCA and BNC exist.(verify)

See also:

Digital video cables (high speed and/or uncompressed)

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Such as:


DVI pinout chart (click for details)

On digital and/or analog

DVI can carry both analog and digital video, but specific wires and interfaces can choose to do just one.

DVI connector variants (male)

In the plugs, there is a plate on one side - if there are pins around that (red in the pinout image on the right), the cable can carry analog video.

If there are pins around that plate, it can carry analog video, and is DVI-A or DVI-I.

if the nearest 3x3 pins are a full block, it's DVI-I (carries analog and digital)
if not, it's DVI-A (carries only analog)

If there are at least two blocks of 3x3 pins, the cable can carry digital video.

if there is no pins around the plate, it is DVI-D(carries only digitial)
if there are pins around that plate, it is DVI-I

If everything is one solid block of pins (that is, includes the blue pins in the image on the right), it can do dual-link digital. If it's not full, it's single-link digital.

There are some other connectors that look roughly like DVI but are incompatible, such as:

And two different many-pin connectors, often seen for many-monitor graphics cards, as each connector can be used for two monitors:

Needs an adapter for things like DVI or VGA (doesn't carry them directly). The absence of pin 58 in DMS-59 seems to be just for keying. It isn't used in LFH either(verify), so you can use DMS-59 cables where you would otherwise use LFH.(verify)

See also:

MiniVGA, MiniDVI, MicroDVI, Mini DisplayPort

Mini-VGA (socket circled, plug on top)

Mini VGA

  • mainly seen in Apple hardware (mostly MacBooks) circa 2005(verify)
  • not standardized, and died out fairly quickly
  • replaced by Mini DVI (which could also go to VGA) and MiniDisplayPort (which does even more)
  • http://en.wikipedia.org/wiki/Mini-VGA

Mini-DVI plug (on an adapter cable for a Macbook)

Mini DVI

MicroDVI, again mostly Apple, was used on some Macbook Airs.

All of the above were discontinued circa 2010, in favour of Mini DisplayPort.

Mini DisplayPort (again, for a Macbook)

Mini DisplayPort

  • Initially in Apple laptops, now adopted by VESA and used by other vendors
  • There are converters to VGA, (Dual-Link) DVI, HDMI, Displayport, and probably more
  • May also carry audio, may not.
  • http://en.wikipedia.org/wiki/Mini_DisplayPort

Other Apple connectors

Thunderbolt socket

Intel and Apple developed Thunderbolt, which uses the same plug as Mini DisplayPort.

...which is intentionally backwards compatible but also potentially confusing,

It's a more generic bus like USB, but the expectations of such are probably still mostly monitor-y.
so e.g. the same Apple monitor will do more on one laptop than another.

It's safe to connect and will display, but any feature beyond that won't work.

You can tell by the logo:

monitor-like logo → Mini DP
lightning-bolt logo → Thunderbolt.

Note that Thunderbolt 3 uses the standardized USB-C (which is now entering general use), so mini-DP-style thunderbolt is now sometimes referred to as Thunderbolt 2 connector.

Lightning plug

Thunderbolt is, by name, confusable with Lightning.

Lightning is the thin flat reversible plug with little strips of connector. It is almost exclusive to iPhone, iPad, iPod, and a handful of Apple accessories. It can do charging, USB data connection, video out, audio out, and apparently SD card reading(verify)

It is being displaced by USB-C, but rather slower than you might expect (possibly because of proprietary sales reasons).


Typical HDMI plug (Type A, 19 pins)

High-Definition Multimedia Interface (HDMI) [5]

Digital transfer. Can carry HD video, and audio. Has hardware-level copy protection (HDCP).

There are plug variants.
HDMI variants
  • Type A is by far the most common, what you usually use
  • Type B has more data lines, designed for very-high-bandwidth applications, but never got used. DisplayPort now make more sense in practice
  • Type C is the mini variant (meant for small/mobile devices)
  • Type D is the micro variant (meant for small/mobile devices)
seen e.g. on Raspberry Pi 4
  • Type E is an automotive variant - locks in place, more resistant to moisture and dirt
you can also get type A in a harness, giving similar features while being compatible with existing cables

(For computers it can be relevant that HDMI can carry DVI-D fairly directly - though this will probably only work if the DVI device supports HDCP, because the HDMI side is likely to require it)

CEC (Consumer Electronics Control) is for simple commands between a set of interconnected devices, e.g. allowing your TV remote to control some common functions of a set-top or DVD player, have a device turn the TV on and to it as a source, control volume, transfer a preferred device name, things like that.

CEC is mostly known under names like Anynet+ (Samsung), 1-Touch Play (Roku), and various names involving 'Link' (lots of brands).

Electrically it is a one-wire bidirectional serial bus, separate from HDMI communication so that everything but this can sleep, and is very slow (~400bit/s) because it doesn't need to be faster.

See also:


DisplayPort plug

DisplayPort [6]

Cable length

Specs say 2 or 3 meter max. This is a cautious figure and decent cable quality may go a little longer, yet don't count on more than 10-20m, and usually only for lower(-data-rate) resolutions.

Active cables could go up to 15-30m at somewhat higher rates/resolutions and a more standard-compliant way. These must be connected in the right direction (passive cables don't care).

If you want more than that, you probably want fiber DP instead of copper (at high enough rates and distances, the issue is capacitance and sort of unavoidable).

A Dual-mode DisplayPort output (a.k.a. DP++) supports the use of an adapter to single-link DVI or HDMI. (a passive adapter in that the output itself already speaks the right thing, the adapter only changes voltages)

Without this, only an active adapter (something that does a conversion between different video formats inside it) would work.

Other conversion formats (e.g. to VGA) always require this.


A single lane (differential pair) in a DP cable can be run at one of four speeds,

  • 1.6GBit/s raw, ~1.3GBit/s data in RBR (reduced bit rate)
  • 2.7GBit/s raw, ~2.1GBit/s data in HBR mode
  • 5.4GBit/s raw, ~4.3GBit/s data in HBR2 mode (introduced in DPv1.2)
  • 8.1GBit/s raw, ~6.5Gbit/s data in HBR3 mode (introduced in DPv1.3)

Cables made for higher speeds will often be 4-pair, which means:

  • 4-pair HBR is ~8 Gbit/s (~10Gbit/s raw minus 20% coding overhead)
  • 4-pair HBR2 is ~17 Gbit/s (~21Gbit/s raw minus 20% coding overhead)
  • 4-pair HBR3 is ~25 Gbit/s (~32Gbit/s raw minus 20% coding overhead)

Your average monitor will just work - e.g. making 1920×1080 not work on a short cable would be very hard.

You would only care about these numbers if you use a combination of 4K, deep color, 120fps, and 3D, e.g.

3840×2160@120fps requires HBR2,
5120x2880@60Hz require HBR3
multiple displays on a single port can be done

Actually thunderbolt, but it's the same plug

Seen used on laptops in general, and Apples in general, for monitors

Also used on Apples for Thunderbolt (1 and 2)

See also:


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Gigabit Video Interface (GVIF), carried by a single twisted pair of wires, also allowing a data channel.

Plugs vary.

Used mostly in a few automotive uses, and then largely video-only. Up to 10 meters, up to ~2GBit.

(Not to be confused with GSIF, GigaSampler InterFace)



UDI (Unified Display Interface) [7] [8]

Seems to never have made it out the door, apparently deprecated in favour of DisplayPort(verify)


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

SDI (Serial Digital Interface) is an uncompressed digital video (and audio) signal, originating around 1989 and mostly seen in professional use.

Electronically: coax with BNC connectors, 75 Ohm characteristic impedance (same cabling as analog video setups, which helped upgrades, but also some confusion), 800 mV peak to peak (but receiver can deal with lower, meaning you could have maybe 300m runs of ~270 Mbit SDI without repeaters).

Speed variants over time:

SD-SDI: ~170..360 Mbit, allows 480i, 576i

ED-SDI: ~500 Mbit, allows 480p, 576p

HD-SDI: ~1.5GBit, allows 720p, 1080i

Dual link HD-SDI (2002): ~3GBit, allows 1080p60

3G-SDI (2006): ~3 GBit, allows allows 1080p60 (and can be easier than dual-link HD-SDI)

6G-SDI (2015)

12G-SDI (2015)

See also:




Network Device Interface is a protocol that amounts to video over IP, and using mDNS for discovery.

It's not a connector per se, but it's recommended to run over gigabit ethernet wires - mostly for bandwidth reasons.

...so it typically implies 8P8C connectors carrying gBit ethernet, and NDI hardware has that as connectors. (You could run it over wifi but due to the speeds this is often not recommended)

It aims at being fairly low latency, and the classical ('Full Bandwidth') NDI is lowish compression. (NDI HX uses H.264, HX2 uses H.265, both with higher latencies)

Things that speak NDI includes hardware devices (cameras, monitors), and varied PC software.

See also Local_and_network_media_routing_notes#NDI for a few more implementation details.

See also



RC-5720, often referred to as TOSLINK. What looks like copper is only there to protect and guide the fiber

While TOSLINK specifies a few plugs, it is mostly associated with the optical EIAJ/JEITA RC-5720 plug, a.k.a. JIS F05 and CP-1201 - optical, mating with a square-ish shape.

In most contexts, this plug carries S/PDIF protocol (which itself can carry raw PCM, DTS, and AC-3).

Note that the exact same S/PDIF signal can also be carried over copper, then often connected via RCA or BNC, which involves fewer components and is really no more sensitive to EM noise - and avoids any conductor so cannot introduce ground loop issues.

You could argue lasers and fibers are cool, but it's just a LED (because cheap and short-range), and something more akin to fishing wire (because more robust). That said, it was ahead of its time, and still not really replaced by another well known standard.

Mini-TOSLINK, which carries fiber to the tip of a 3.5mm TRS-shaped plug

Mini-TOSLINK looks like a stereo jack (3.5mm TRS style) but carries the light to its tip.

There are physical adapters from TOSLINK to mini-TOSLINK.

This allows laptops (and other size-restrained devices) to have one small socket that provides both an analog stereo 3.5mm output, and digital audio output, in one.

See also:


Power supply

AMP/Molex power and Berg power connectors

AMP Mate-n-Lok / Molex 8981, plug (top) and socket (bottom)
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Molex in general is a company that makes many types of plugs.

This one has confusing history. As far as I can tell right now:

AMP Mate-n-Lok (left), Early Molex (right)

There was a Molex connector (early 60s?) that was close to the plug we later knew in PCs (the right one on the image with blue background), but incompatible.

AMP in 1963 introduced Mate-n-Lok (starting around 1976).

...which became used in PCs and common enough that in 1983, Molex brought out Molex 8981 which was fully compatible (basically the same) with AMP Mate-n-Lok.

As such, the thing we called Molex around computers for the next couple of decades (seen on larger floppy drives, on PATA HDD and PATA CD/DVD drive connections) is either AMP Mate-n-Lok or Molex 8981. Calling it AMP Mate-n-Lok is slightly more accurate in that it doesn't ignore the decade of use that established the connector, but practically there is no difference.

The plug has, in most uses, now been displaced, mostly by SATA power plugs.

(also, AMP is now called TE, but the connectors are still called AMP for findability)

A Berg plug, AMP 171822-4

The Berg plug (apparently named after its designer) was mainly used on 3.5 inch floppy drives.

While sometimes called 4-pin mini-Molex, this one is also an AMP plug, specifically AMP 171822-4 for the cable socket, AMP 171826-4 for the right Angle PCB header.

These plugs are becoming as rare as floppy drives themselves.

See also:

PCIe, EPS, etc.

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

These connectors seem to come from the Molex Mini-Fit family - most resembling a Mini-Fit Jr though actually seems to use a different keying(verify)

8-pin PCIe and 6-pin PCIe sockets on a GPU (note the left three columns are the same)

The 'PCIe' naming seems to come from the fact that PCIe video card power draw is high enough that it is not sensible to get it through mainboard traces / the PCIe bus, so we decided to get it through a plug like this instead.(verify)

PCIe 6-pin (mostly seen on GPUs)

officially: two pairs of +12V and Gnd (the last pair is specced as NC)
unofficially often three pairs of +12V and Gnd (most such cables and PSUs allow real current draw on the third)

PCIe 8-pin - an expansion of the 6-pin (mostly seen on GPUs)

Three pairs of +12V and Gnd
with the pin that the 6-pin variant listed as NC now guaranteed to be a +12V
A plug may separate the 6+2, to be compatible with both 6-pin and 8-pin variants
the extra 2 add a Gnd and Sense

There seems to now also be a 12-Pin variant for nVidia RTX 3xxx series, apparently for space reasons, in that you can use an adapter from two 6-pins.

4-pin ATX 12V plug

4-pin ATX 12V (mostly seen on motherboards)

Two pairs of +12V and Gnd
used for power more directly to the CPU, has been around since roughly the pentium 4

8-pin ATX 12V

Doesn't exist and, assuming you said it because motherboard, will probably mean you're looking at 8-pin EPS12V (verify)

8-pin EPS12V socket on a motherboard

EPS 12V [9] (mostly seen on server motherboards)

Mostly seen on server boards (and some higher-power consumer boards), meant for more current to the CPU.
It is not ATX standard - but is effectively a derivative of it, defined by SSI
The 8-pin EPS connector is four pairs of +12V and Gnd
physically incompatible with PCIe 8-pin
the 4-pin EPS connector is two pairs of +12V and Gnd(verify)
this plug seems less common than the 8-pin(verify) (probably because 4-pin ATX 12V will do)

4+4 EPS/ATX (on power supplies)

Refers to plug only: splittable, so that a PSU needs fewer wires and plastic to accomodate both 4-pin ATX and 8-pin EPS motherboards sockets
That split cheats a little, but it is hard to plug incorrectly unless you get particularly creative with adapters or hammers.
In practice, a lot of consumer power supplies just give you both a 4-pin ATX and 8-pin EPS12V, which is less confusing

See also:

Fan connector

3-pin fan plug in 4-pin (intel-style) connector
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

PC fans are often connected with a three-pin connector (polarized variant from the Molex KK family) which supplies 12V, ground, and a sensor wire that the computer can use to count revolutions.

There were a few not-so-standard variation, such as Dell's.

You now commonly see Intel's variation, with a fourth pin to the side.


  • 1 - Ground (black)
  • 2 - 12V (often red)
  • 3 - speed sense (often yellow)

4-pin adds

  • 4 - PWM signal - seems to often be a voltage signal that the fan uses via a transistor(verify)

6-pin (seen in servers) add:

  • 5 - fan presence (lets the computer do a simpler test to see there is one connected)
  • 6 - fan fault led (for visual feedback which one is broken, useful in datacenters because of cramped hardware layouts and loud environment)

As the larger sockets are physically an extension on the simper ones, this is often fairly compatible -- as long as you know which one is pin 1, which bits of keying plastic usually help with.

3-pin fan on 4-pin header is fine, will run at full speed - because they don't even know about the PWM pin
most 4-pin fans are designed to work fine on a 3-pin header

Lower speeds

You can undervolt a fan with a ghetto-ish fix: splice a fan between the +12V and +5V (e.g. from a molex plug) giving 7V.

However, not all fans spin up reliably at voltages like 7V, so check that it does or you'll have no cooling at all. This is is also why using a potentiometer for speed control is less predictable than it seems.

Using PWM is the preferred method of speed control over lowering voltage e.g. with a potentiometer, because PWM will typically work down to lower speeds than undervolting (for an combination of reasons that is a little complex).

On the 3-pin variant, motherboards officially just put 12V on the power pin. Some motherboards would instead just PWM the 12V line, which works even on 3-pin fans, but has some footnotes.

This is what 4-pin fan connectors instead adding a separate pin with PWM signal (the fan has a transistor that combines it with the 12V line), which is a more standard way of doing PWM.

If you have a 3-pin fan and a 4-pin fan socket, a little soldering you can make a 3-pin fan PWM capable (transistor and resistor, optionally a diode), but 4-pin fans basically cost the same, so this is generally not worth doing.

Note that there are little speed control boxes you plug between motherboard and fan. Which are often but not always PWM based.



You can reasonably distinguish PATA from various other 40-pin IDC plugs from that one filled hole. The plastic alignment notch is also fairly common)

IDE (Integrated Drive Electronics) a hardware bus primarily a ssociated with ATA and its protocol.

IDE can however also refer to some pre-ATA and other not-ATA things.

Once ATA was standard, IDE and ATA were used more or less interchangeably.

Once SATA existed, a distinction between SATA and IDE(-as-in-parallel) became convenient, so both IDE and ATA became a bit vague, and we started using SATA and the retronym PATA (Parallel ATA) became a clearer way to refer to this 40-pin connector.


  • If there are two devices on a single PATA cable, one is called master and the other the slave (jumpered that way, or sometimes implied via its position on the cable)
These names are not official. They also do not refer to interaction between the drives at all - both drives operate independently, using their own controllers and both only talking to the host. It was just a way for the host to distinguish between two on the same cable.
  • There was also EIDE, Enhanced IDE, referring more vaguely to early adoption of some features of a then-future ATA standards. The term was also abused by marketing at that time


'ATA with Packet Interface Extension' is actually about protocol, not plug - it can be carried over PATA or SATA.

ATAPI is an extension based on SCSI protocol features, that made it more useful for certain (additional) drive types, such as CD, DVD, and tape drives.

In this context, ARMD ('ATAPI Removable Media Device') was mainly used to refer to ATAPI drives other than CD/DVD drives. Often meaning tape drives.

Early CD drives: Panasonic, Sony, and Mitsumi

Before ATAPI caught on as the standard for CD drives, and multiple ATA controllers became common on motherboards, these three companies created proprietary interfaces (sometimes called AT-BUS and other things) to connect CD drives of their own styles.

the relevant end of a Sound Blaster 16 card

Certain expansion cards, e.g. the Sound Blaster 16, exposed these connectors as a simple way to connect these pre-ATAPI drives without needing another specific interface card. (TODO: look up the details)

Sony used a 34-pin IDC/ribbon connector.

Panasonic and Mitsumi used 40-pin IDC/ribbon connectors (that were potentially confusable with PATA connectors, particularly when used for later CD drives that use ATAPI).

Side note on ATA

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

ATA refers to "Advanced Technology Attachment", effectively a set of standards that encompasses Parallel ATA, ATAPI, Serial ATA (SATA), and more.

ATA versions and introduced features:

  • pre-ATA standards had varied limits, particularly in the DOS era
  • ATA-1 (1994) - PIO 1 and 2, 28-bit LBA for sizes up to 137GB
  • ATA-2 (1996) - PIO 3 and 4, DMA 1 and 2 (the terms 'EIDE' and 'Fast-ATA' appeard around this time)
  • ATA-3 (1997) - SMART, connector for 2.5" drives
  • ATA-4 (1998) - UDMA 0, 1, 2 ('UDMA 33')
  • ATA-5 (2000) - UDMA 3, 4 ('UDMA/66')
  • ATA-6 (2002) - UDMA 5 ('UDMA/100'), 48-bit LBA for sizes up to 144 PB
  • ATA-7 (2005) - UDMA 6 ('UDMA/133'), SATA 1.0 ('SATA/150')
  • ATA-8 (in progress; there is a working draft you can get)

SATA has its own versioning: [10]

  • SATA 1.0
  • SATA 2.0 (2004)
    • SATA 2.5 (2005)
    • SATA 2.6 (2007)
  • SATA 3.0 (2009)
    • SATA 3.1 (2011)
    • SATA 3.2 (2013)
    • SATA 3.3 (2016)
    • SATA 3.4 (2018)


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)
SATA data sockets variant with shroud that makes it a little sturdier and accepts a clip
SATA data plug (without clip)
SATA power connector (15-pin)

SATA: Serial ATA, is part of ATA-6 and later. Has basically replaced PATA.

There are variants, but most of us care about the 7-pin data cable (and the 15-pin power cable).

The data socket can be as minimal as just the plastic to hold the contacts, but most sockets are a variation with a plastic shroud (see first image), making it harder to break. This will also accept the clip present on some cables.

Basic SATA's basic power connector has so many pins for scalability reasons - it provides three voltages (3.3V, 5V, 12V), with three pins each to be able to meet requirements of power hungry drives (while not exceepding 1.5A per wire), plus one signalling cable.

This cabling is often not necessary, and there are slimline and micro versions of the power connector, which use simpler wiring, and are good enough for the drives they're meant for.

eSATA plug

For external use there is eSATA, which is pin-compatible and functionally identical. The main differences lie in electronic, cable length, and physical specs, and the connector and socket are different enough so that you can't plug SATA cables meant for internal use onto external ports. (There are dumb adapters, but you should be aware of what you're defeating, and will also have trouble around SATA ports that disable themselves at boot if there's no drive on there)

eSATAp socket, accepting eSATA and Type-A USB plugs. There are also combinations that accept USB3

There is also eSATAp (often marked eSATA+), which is a connector that adds power, and the ability to plug in USB into this same socket. Keep in mind that this may be either USB2 or USB3 (you can usually tell by the color).

eSATAp is a variant of eSATA that carries also carries power -- and also USB.

Only SATA's 5V line is guaranteed on this plug, the 12V line is optional. Desktop computers typically provide 12V, while laptops often don't(verify).

This means eSATAp sockets can typically power 2.5" drives (which only need +5V), but only the desktop variants can power external 3.5" drives (which also need 12V).

eSATApd unofficially refers to having both voltages.

See also:


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

SAS and SATA are quite similar, and in many areas compatible.

This is by design. You could see

  • SAS (Serial Attached SCSI) as the fancier variant of SATA that targets the business market, adding more options and features, more practical variations in controllers, cables with more channels to attach more drives (and have cable failover), options to connect externally as well (e.g. drive bays), and other such options.
  • SATA as the simpler, one-drive-at-a-time consumer variant
(well, with footnotes. There were things like SATA port multipliers but controller support varied)
that is simpler to use cheaper to make

The protocol is also very similar, though SATA's requires command is a subset of SAS's(verify)), both are switched, point-to-point, serial, full-duplex, can transfer approx. 300MByte/sec per port (current typical; both have variations and plans), and can be hot-plugged (electrically, anyway. Your BIOS and OS may have their ideas about enabling and resetting ports).

SFF-8482 plug. Drive bays may have similar mounted on PCBs
Back of a SAS drive, SFF-8482 style.
Pin-compatible with SATA, but the plastic tab in the middle prevents mating SATA as-is

The SAS drive interface is SFF-8482 - the one that that looks a lot like SATA, and can connect SATA as well as SAS drives.

The SAS and SATA drive connections are closely related, and in fact pin-compatible. You can physically plug SATA drives onto SAS controllers, the SAS drive connector (SFF-8482) allows it, and SAS can tunnel SATA. This means server backplanes are easily designed to take SAS and SATA alongside each other.

SATA cannot tunnel SAS, and for this reason you cannot use SATA cabling on a SAS drive. Physically because of the extra plastic, but even if you find a physical adapter (they exist, though I'm not 100% on why), it probably won't work(verify).

Beyond single drives

Because of varied use cases, there are a whole bunch of internal connectors standardized by SAS, e.g. to carry a handful of channels between drive bay backplane and controller.

Many of them are used more in servers, but some of them are obvious choices in handful-of-drives consumer RAID hardware as well.

See e.g. [11]

See also:


mSATA (left) and M.2 (right)

Uses the more general PCI Express Mini Card ('mPCIe') connector as a small drive connector (data+power).

...which caused some confusion, because some sockets were mPCIe, and some mSATA-only (verify)

Was seen in smaller laptops and such for storage, where it is now mostly replaced by M.2

See also:


A form factor spec for expansion cards in general, standardized around 2013 (then known as NGFF (Next Generation Form Factor), before it was renamed to M.2)

Can carry include SATA 3, NVMe, USB 3, and (multiple lanes of) PCIe 3.

Does not support/guarantee hot-swap. But there are specific cases where this works.

Consumers mainly see this used for storage, in which case you can consider it a replacement of PCI Express Mini Card connector (and its use for mSATA).

If your PC doesn't have M.2 on-board, there are PCIe plug-in cards with M.2 sockets. If your laptop doesn't, you probably can't use it.

Also keep in mind that it's new enough that not all current systems can boot off M.2 - in which case you can't (easily) use it for your system drive. So you want to check that. And there's no upgrade path other than upgrading at least half your computer's hardware.

Widths include 12mm, 16mm, 22mm (which seems most common) and 30 mm

Lengths include 16, 26, 30, 38, 42, 60, 80 and 110 mm

The basic shorthand is those two appended, e.g. 2280 for 22mm by 80mm

A shorthand with more dashes, like WWLL-HH-K-K or WWLL-HH-K, encodes more details (like single/double-sided, maximum thickness of components, and more)

The notchings (specific gaps in the socket/connectors) are intended to not allow inserting into certainly-incompatible hosts. There are about a dozen of them, but half of them are currently reserved.

If you can plug it in it should not damage anything, but it is also not guarantee it will function as expected.

Notchings are correlated with use. For example:

B and M are wider use (including PCIe lanes), in practice mostly used for SSD (SATA and/or NVMe)
B has one side has short piece with 6 pins
M has one side has short piece with 5 pins
BM has both of those notches
For WiFi you'll see A and E (verify)

For more practical reasons, notchings are also somewhat correlated to sizes, e.g.

A and E are rarely longer than 30,
while B and M may use up to the full length, and rarely as short as 30.

See also:

M.2's relation to NVMe

NVMe is storage over PCIe communication.

Which makes NVMe an alternative protocol to SATA when connecting SSD drives.

Pluggable storage that speaks NVMe currently correlates strongly to M.2 connectors - so M.2 and NVMe are often seen as roughly the same thing, and used as near-synonyms by some.

Which is sort of wrong - M.2 can carry both SATA and NVMe.

When M.2 carries NVMe, it allows higher bandwidth (which most SSDs don't need yet), and also : has queues that makes it easier to use the parallelism of fancier SSD designs (e.g. allowing parallel reads), which makes it potentially faster and lower latency than SATA SSD.

How much faster is frequently overstated -- for now. It's much more a "potentially better", and headroom to be a good interface for a good number of years, much less a guaranteed to be better right now.

More to the point, even if it would for best-case benchmarks, in practice it depends a lot more on the actual workload than the marketing graphs would like you to realize (which is the point of these graphs, of course) because those were made on very specific workloads.

Rather than five times faster everything, you may find increase on most everyday use is more like a few percent to a few dozen percent. Cases that may see a little more may include some servers, some video editing, some games see a modest difference (in loading time, and then only to the degree it is not bound by something else).

So whether the price/performance is worth it depends the same way.

That said, NVMe it is preferable for SSD so is likely the preferred interface for SSD in the future(verify).

See also:

Apple's SSD connectors

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Apple 6+12 pin SSD connector

Apple has used various different connectors over time, none of them M.2.

They include:

  • 'first generation', a 6+12 pin (around 2010) (carries mSATA III(verify))
  • 'second generation', a 7+17 pin (around 2012) (carries mSATA III(verify))
  • 'third generation', a 12+16 pin (around 2014) (carries PCIe (verify))
with a later variation that uses a 40 pin mezzanine adapter (verify)
  • 'fourth generation', (~2015) same connector, but higher speed (verify)
  • 'fifth generation', (~2016) same connector, but higher speed and speaks NVMe (verify)

There are often physical adapters from M.2 (the protocols these things speak don't seem to differ), letting you use more generic SSDs, but you must do the research both on compatibility and whether it will fit.



First years's most common set:
mini-B plug,   B plug,   A socket,   A plug
Various plugs in wiring diagrams
Also shows the micro versions, and the mini-A not in the picture above
USB3 A plug: the four classical pins, and 5 new ones further in
USB3 B plug
USB3 micro-B plug
USB-C plug
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Roughly from most to least common (well, a guess at that):

  • USB A: The plug/socket seen on the computer side and USB hubs (and sometimes elsewhere, e.g. on printers for direct camera connection)
  • USB B: Used on the device side for bulkier devices, such as scanners and printers, where there are no space limitations, and sturdiness is handy
  • USB-C: Invertible. Seen on smartphone, some apple products. (released ~2014.
Developed parallel to USB3, and as of this writing the two don't support all the same features (verify)
  • USB micro-B plugs and sockets, meant for use in thinner devices. example: smartphones data/charge cables.
  • USB mini-B: Used by various smaller devices, such as cameras, MP3 players, some phones
  • USB3 A: Plug adds the extra lines for USB3, but remains the same size. Socket can take earlier (USB1, USB2) USB A.
  • USB3 B: Plug adds the extra lines for USB3, and is bigger. Socket can take earlier USB B.(verify)
  • USB3 micro-B - basically USB2 alongside USB3(verify), separated with a notch. Seen e.g. on 2.5" external hard drives, USB3 hubs.
  • USB3 Micro-A (looks like USB3 micro-B but squarer) exists only as a plug, and seems rare
  • USB3 Micro-AB (looks like USB3 micro-B but squarer) refers to a socket that takes USB3 Micro-A and USB3 Micro-B, also seems fairly rare
  • USB mini-AB socket (socket only), relatively rare, can accept both Mini-A and Mini-B plugs.
  • USB micro-AB socket (socket only) that can accept both Micro-A and Micro-B. Defined by USB On The Go (OTG) (2001 standard)
  • USB micro-A plugs and sockets, meant for use in thinner devices
  • USB mini-A: was never seen that much, perhaps because it is confusable with mini-B.
  • There are many non-standard plugs that are relatively rare.
Say, I've seen cameras use approximately-8-pin sockets with different cables that connect either USB, or things like audio+video. This plug is sometimes confusingly called B(-type).


  • USB 2 has four pins:
    • power lines are 5V and ground
    • data is 3.3V differential
  • the fifth pin on micro plugs is OTG ID, and is either tied to ground (marking that side as host side) or floating (marking it as device side) (verify)
leaves all those USB2 in there
adds five more:
two differential pairs
and a ground
  • USB version 3 are often indicated with either blue plastic, or SS (for Super Speed, the mode that USB3 adds)
micro plugs/sockets are often not blue, possibly because it would be hard to see anyway(verify)), and because they're less ambiguous that PC-side A sockets
  • The USB1/2 mini connectors are approximately 3mm by 7mm, the micro versions are mostly just thinner, making them useful on very slim devices like smartphones.

See also:

8P8C / Ethernet cable

Ethernet cable (8P8C plug, with colors indicating TIA/EIA-568-B wiring)

For the series of connectors, see #Modular_connector_.28and_Registered_Jack.29.3B_.3FP.3FC

For the use of 8P8C in ethernet, see 8P8C / RJ45

Firewire (IEEE 1394)

The 6-lead plug
The larger 6-lead connector and smaller 4-lead connector
both Firewire-400
The 9-pin Firewire-800 plug, 'beta'
which can also be used for S1600 and S3200
IEEE1394c allows Firewire at 800MBit over 8P8C/Cat5 cabling
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

IEEE 1394 is better known as FireWire (Apple), and sometimes i.LINK (Sony), and Lynx (Texas Instruments).

It was meant as a successor to parallel SCSI, and is also commonly used for some digital cameras, and for high-end audio and video devices. Was a potential competitor to USB in many areas, but while USB is somewhat slower (depending on which variant of FireWire and USB), USB is more popular for many things.

Connectors include:

  • 4-lead
    • smaller, e.g. used on more portable devices like cameras. Data-compatible with the 6-lead connector, but doesn't provide power. Initially developed by Sony, later more widely adopted(verify)
    • two twisted pairs of data
  • 6-lead ('alpha')
    • two twisted pairs of data, power
  • 9-lead ('beta')
    • two twisted pairs of data, power, shield (verify)
  • 8P8C connector (used in 1394c)


  • IEEE 1394, specifically IEEE 1394-1995
  • IEEE 1394a, specifically IEEE 1394a-2000, also known as FireWire 400
    • Uses the 4-lead and 6-lead ('alpha') connectors
  • IEEE 1394b, specifically IEEE 1394b-2002, also known as FireWire 800 (Apple's name)
    • adds the 9-lead ('beta') connector
  • IEEE 1394c, specifically IEEE 1394c-2006, also known as FireWire S800T
    • adds the 8P8C connector

See also:


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Fast peripheral interconnect by Intel and Apple. (Developed by Intel under the name Light Peak, since renamed)

Thunderbolt (1/2) socket

Thunderbolt 1 reuses the Mini DisplayPort connector; thunderbolt capability is indicated by a lightning symbol.

Can carry DisplayPort, one or more PCI Express lanes, and up to 10W of power.
Copper cables carry two 10GBbps (1.2GByte/s) lanes, of which any device can use only one (seems a fair-sharing thing)
Assume ~3 meter max over copper(verify)
Can daisy-chain a few devices (though individual devices have to have the plugs for it, and allow it)(verify).

Thunderbolt 2

Much like 1. Largest difference seems to be that a device can use both channels(verify)

USB-C plug. If it's got a bolt near it, or you'd expect it in context, it's thunderbolt 3.

Thunderbolt 3 uses USB-C connectors. Plugs and sockets should bear the thunderbolt logo to lessen confusion.

Speaks more protocols (DisplayPort, PCIe, USB 3, ...)
Allows adapters to the previous MiniDP plug
Not guaranteed to carry 10W as before (though USB could choose to do more than that) (verify)
Assume it can do 20Gbps as before. Short or active cables could do 40Gbps(verify)

On Thunderbolt 3, USB3, and USB-C

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

USB-C USB-C diagram.png is more a physical connector than anything else.

It is intentionally protocol-agnostic, and there are already a handful of protocols that can be negotiated on top, including

USB3.1 (5 or 10GBps), USB3.2 (20GBps)
USB2 Hi-speed (0.48GBps)
USB Power Delivery
Thunderbolt 3 (10GBps, 20GBps, 40GBps(verify))
just video (DisplayPort, HDMI, MHL)
...or some combination.

It is context-dependent which protocols the endpoints care to speak.

This is both nice and potentially confusing. Yes, it reduces the amount of connectors you need and makes USB more universal.

But also, there will be various lots of incompatibilities and confusion that won't be easy to explain to everyone.

Say, Thunderbolt 3 chose USB-C plugs/cable (previous versions used mini-DisplayPort), so TB3 can in many contexts be seen as an extension of USB3. But a Thunderbolt3 device will do nothing on a USB3-only host. Probably.

USB-C cables are created roughly equally, at least in theory.

In practice,

not all cables support the same speed
it may be capable of sustaining 40Gbit, 20Gbit, 10Gbit, 5GBit, or even just 480Mbit(verify)
and which of the standards (TB3, DP, USB3, USB2) and which of their modes will work may vary
not all cables support charging (verify)
and if they pretend to do so, but are out-of-spec knockoff cables, this is riskier these days, because there is more current involved than in earlier USB


PS/2 plugs, on USB-mouse-to-PS/2 adapter and USB-keyboard-to-PS/2 adapters, respectively
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Uses the 6-pin mini-DIN connector. For keyboards, this replaced the larger DIN plug used on AT style computers before PS/2. For mice, this became an alternative to serial port mice, though USB is now also quite common for keyboards and mice.

D-sub (D-subminiature)

The sizes (widths) of various D-sub plugs
DE-15 (also seen named HD-15, DB15, HDDB15), used for VGA monitor connections
Back of a computer with DB-25F (parallel port), DE-15F (VGA connector), DE-9M (serial port).
The DA-15M held next to it is a MIDI-on-a-gameport cable
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

D-subminiature have a keystone-shaped shell for seating and earthing, and typically fastened with screws.

Most have two rows of pins, some three.

Spacing of pins within a row is 2.76mm, rows are 2.84mm apart. (2.3 mm and 2.0mm in HD variants(verify))


  • The second letter indicates the shell size (A through E),
  • followed by the number of pins present,
  • and sometimes the M or F for male/female (originally P and S for plug and socket)

Given the shell size and pin spacing, there is a typical amount of pins for each size of shell when there are 2 rows: 15 for A, 25 for B, 37 for C, 50 for D, 9 for E.

There are however exceptions, like the three-row variants (e.g. DA-26, DD-50, DE-15), and sometimes other things in there (e.g. DB13W3).

Some common examples:

  • DE-9: often a serial port (RS232) interface
  • DB-25: Parallel ports (also once for serial ports, with inverted gender), sometimes (older) SCSI
  • DE-15: VGA monitor connectors. (Uses three rows of pins. Also technically called HD-15, where HD stands for the High Density of the pins compared to other D-Sub plugs)
  • DA-15: On older PC sound cards, this is a game port, originally for joysticks, later more for MIDI cables

Some people abuse specific letter codes thinking that they referred to the D-sub plugs in general, and started patterns of misleading use for those that do know what they mean, e.g. DB15 to refer to DE15 (VGA) or DA15 (gameport).

There are smaller variants called Micro-D and Nano-D, mostly seen in military and space use.


34-pin floppy cable plug on the left, a 40-pin parallel ATA plug on the right (the latter recognizable by the one filled hole, and the plastic alignment notch is also fairly common)

The plug is called an insulation-displacement connector, IDC (see also DIN 41651).

In computer (building) circles it is common to refer to IDC on ribbon cables as just ribbon cables, not naming the plug.

The IDC pitch (hole spacing) is often 2.54mm (0.1 inch), though there are variations.

For example, parallel ATA connectors for laptop disks often had 2.0mm pitch.

Common IDC plug variations in computers:

  • 40-pin (2x20, 2.54mm pitch - 3.5" hard drive connectors (parallel ATA)
  • 44-pin (2x22), 2.0mm pitch - 2.5" notebook hard drive connectors (parallel ATA)
  • 34-pin (2x17), 2.54mm pitch - floppy connectors (controller side, and drive side for 3.5" floppy drives)
also old Sony CDROM drives, see above
  • Some motherboard-connected ports not directly on motherboard, e.g. an extra serial port, audio connectors (varying pin details), extra USB ports (varying pin details), and more
  • used internally in a lot of places, which may be more case-specific and less standard than various of the above.

See also:

Micro ribbon

Female 36-pin micro ribbon connector, seen e.g. on printers before USB became a thing
Male 36-pin micro ribbon connector, seen e.g. on printer cables, as introduced by Centronics
Female 50-pin micro ribbon connector, here used to connect SCSI-1
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

The shell's shape is like that in D-sub, but the connectors are strips, not pins, and fastening is clips, not screws.

Perhaps best known for use in

  • 36-pin: IEEE 1284 printer cables, specifically a male DB25 plug to male 36-pin Centronics plug (this use is mostly outdated)
This variant and use is also known as the Centronics connector, as they introduced it. People will call more variants Centronics because of this association.
  • 50-pin: SCSI-1 (also mostly outdated)

Also used in

a telco connector [13]

It is apparently also known under names like Contronics, telco, 25-pair, miniature delta ribbon, mini D ribbon, delta ribbon, MDR, Amphenol, and CHAMP.

Now rarely seen.

Confusable with:

See also:


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Mini-centronics looks like micro ribbon (a.k.a. centronics), but thinner.


(Used to be) Most likely recongized as 'something to do with SCSI', though it also sees other uses.

Uses seen:

  • 36-pin: printer cable (as a compact version of the basic Centronics 36-pin)
  • 50-pin: SCSI-2, SCSI-5
  • AAUI?

Mobile devices

Memory cards

See also http://en.wikipedia.org/wiki/Comparison_of_memory_cards

SD and MMC

Sizes and basic pins (not showing extra UHS pins)

Physical size: There's mainly

  • SD (24x32x2.1mm)
  • microSD (11x15x1.0mm)
previously called TransFlash (abbreviated TF and T-Flash), and some parts of the world still prefer that name
  • There's also MiniSD, which never really took off

The variants are pin-compatible (some footnotes on the faster ones with extra pins), so adapters to larger sizes exist, and the choice of which you want relates more to the device. For example, cameras and laptops and generic card readers often prefer SD, which is a little sturdier and less fiddly to move around, smartphones use microSD because of the smaller size and it being more or less permanently in there anyway.

Storage size:

When released around 2000, they were tens of megabytes large (apparently allowed for up to 2GB(verify))

SDHC (~2007) allowed up to 32GB

SDXC (2009 and later) allowed sizes up to 2TB, and optionally allowed designs that go at higher speeds.


Basic speed is 12MB/s, or 25MB/s when clocked at double rate

UHS variants go up to 100MB/s or a few multiples of that, depending on the variant, and on card and reader support.


  • readers that are connected via USB2 will implicitly be limited to ~40MB/s in theory but often ~25MB/s in practice, regardless of capability of card controller or SD card's capabilities.
  • there are a few footnotes to compatibility, e.g. that the newest generation are not guaranteed to work in the oldest readers

See also:


In today's context, MultiMediaCard (MMC) (since roughly 1997) was the predecessor for SD cards (since 1999).

Because SD builds on MMC both physically and in terms of protocol, many SD controllers will still accept MMC cards.

Variants of MMC (some of them specialized or local) have come out until recently, but MMC is generally much less common than SD cards.

Like SD, MMC had some size variants (see e.g. MMCplus, MMCmicro). More than the later SD, in part because it was an open standard so let companies roll their own.

Worth mentioning is eMMC, basically a flash chip meant for internal use, that happens to be built on MMC. It was in common use for internal storage in phones and tables until it was displaced by UFS.

See also:

CompactFlash (CF)

Type 1 Compact Flash (CF)
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Basically a PATA bus, and talking ATA.

Often contained flash (which was initially fairly small), though initially also for very small hard drives (microdrives).

It offered good features early on (compared e.g. to SmartMedia), but was later displaced by smaller and faster formats - though the sturdiness let it hold on in certain uses, e.g. photography where huge storage size is less important.

Physical size: 36m high, 43mm wide

Type I is 3.3mm thick
type II is 5mm thick

Type II was mostly used by microdrives, also because II is allowed to draw more current than I. As microdrives were fairly quickly displaced by flash-based storage, most CF cards are Type I, and not all devices do not fit Type II cards(verify).

There are derivations, like CFast (SATA bus) and CFexpress (PCIe bus) but these are essentially different formats.

Storage size

Initially, sizes were dozens to hundreds of MByts, because when it was design (mid-nineties) a GByte was more storage than a lot of PCs had. In the 2000s they grew to dozens of GBytes.

Recent CF5.0 allows much larger, though in a lot of uses a hundred GByte or so is more than you need, and larger may be better served by a more modern, faster format.


Because it's really just ATA, the maximum speed varies with ATA version.

Original specs were limited to PIO modes, which top out around 25MB/s.

Later UDMA modes supported up to 166MB/s, and some CF is actually that fast, which is still on par with modern SD cards.

Yet regular CF didn't go much faster than 20MB/s or 30MB/s from decent cards(verify), and maybe single digits from cheap ones (note: like cheap SD today). (probably in part because various ways of reading out didn't go much faster anyway - card readers were often USB2 at the time, which doesn't often go faster than 30MB/s, and some IDE to CF adapters lacked the faster modes(verify). Also, older devices that used CF might not support newer (UDMA) modes without a firmware update, or at all.)

The x speed rating is multiples of 150KB/s (like in CDs), so e.g.

133x is approx 20 MB/s
1066x is approx 160MB/s.

Note that the listed speed is usually the read speed, not the write speed.

See also:

Memory Stick (Duo, Pro, Micro (M2), etc.)

MSst duo m2.jpg
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

The three sizes are electronically largely identical, and adapters from M2 to Duo-size and standard-size exist.

Seen on mobile phones, cameras, The PlayStation Portable, etc. Competed mainly with SD and CF at the time.

Memory size:

original: 128MB
PRO: 32GB (probably the most common)

There are three physical sizes (which you could call Standard, Duo, and Micro):

  • that of the Memory Stick Standard, PRO (longer and thicker than the Duo)
  • that of the Memory Stick Duo, PRO Duo, PRO-HG Duo (shorter and thinner than the standard)
  • that of the Memory Stick Micro (M2)

If you haven't seen them before

the Standard and Duo's angled corners make them somewhat confusable with SD.
The size of the micro (M2) makes it somewhat confusable with the microSD.

See also:


A few types, sizes up to 512MB and 2GB varying with them.

Apparently quite similar to SmartMedia


SmartMedia (SM)

  • quite thin (0.76mm), feels fragile
  • capacity limited to 128MB (...so not seen much anymore)

See also:

RF/coax connectors

Plugs desiged (mostly in terms of shielding and impedance) to carry radio frequencies, associated with carrying video, data, and more.


Belling-Lee (IEC 169-2)

Both ends of a Belling-Lee extender cable

Used for TV (and radio) connectors in some European countries, and Australia.

Diameter is 9.52mm.

Some people seem to call this a PAL connector, probably through association with the countries this is seen in.

Some call it a coax plug, which is even vaguer.

Note that on houses with more serious installations, it's not unusual to see these only in the eventual wall-plug and the cable that goes to the TV, and something like F collectors on cabling (and signal boosters) before that. This because the Belling-Lee plugs are not ideal for VHF and UHF frequencies (but fine for MW and Shortwave) so you really don't want them more than once in your chain if you can help it.

See also:

F Connector (IEC 169-24)

F Connector

Diameter: ~14.5mm

Often used for cable television / cable modems, satellite television, and (American) TV aerial connections.

A little less lossy for VHF and UHF than Belling-Lee is, so is seen in more places in infrastructure(verify).

See also:


BNC connector on an old network card (the plastic thread is meant for a fastening ring and is not part of BNC(verify))

Diameter: ~13.5mm

BNC, Bayonet Neill-Concelman (apparently also sometimes Baby Neill-Concelman connector, Baby N connector, British naval connector, bayonet nut connector) was once common for networking. Still used for some antennae, video (then often composite video), occasionally audio and other things because it's coax (so shielded).



TNC connector

TNC, Threaded Neill-Concelman, is a variation on BNC with a screw thread system (BNC uses bayonet).

Diameter: ~14mm

R-TNC (Reverse TNC) connector for the antennae on a WiFi access point (note that the smaller R-SMA is also common there)

Reverse TNC is reverse in that the inward/outward threading is switched between male and female plugs. This is seen e.g. in older/larger WiFi antennas, an area where the smaller R-SMA is also regularly seen for the smaller ones(verify).

See also:

C connector

C connector (left), beside a BNC connector (right) for an impression of size
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

The Type C Connector looks like BNC, but is bigger.

(BNC was developed as a smaller version of this [14])

See also:

SMA and reverse SMA

SMA (male)
SMA (female)

Diameter: ~6mm for the thread/female, ~8mm for the male/outside

SMA is short for for SubMiniature version A. There are also SMB and SMC connectors.

RP-SMA / RSMA (male) (on a PCI WiFi card)
RP-SMA / RSMA (female) (on an antenna for that same card)

A variation on SMA called RP-SMA ('reverse polarity') is used in WiFi antenna connectors (the larger R-TNC also sees use there, mostly on older APs).

See also:


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Diameter: ~4mm for the thread/female

See also:


See also:


Some size reference
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)
Close-up; U.FL connector on the left (top right of the PCB), and plug held in the calipers on the right.

These various names all refer to tiny connectors for high-frequency RF signals (up to approx 6GHz), and seem mostly interchangeable(verify). Seen in various mobile and wireless applications.

There are adapters to things like (RP-)SMA sold for applications such as WiFi, mobile modules (particularly M2M[15]), and others.

See also:

Unsorted RF connectors

CRC-9 (3mm)

TS-9 (3mm)

MMCX (2.5mm)

MC-Card (2mm)

Power - device side

Low/medium voltage, device side

...e.g. adapters, battery packs, solar panels, and such.

Meaning up to a dozen volts, generally up to an amp or two.

DC connectors, EIAJ power, coaxial and more

A bunch of them (see list on the left)
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Usually used for low-voltage power, most under 20V, and (so) typically used for DC.

Up to a few millimeters thick, often either concentric barrel-style or tip-(ring-)sleeve style.

Most are not so much standardized as they are used by convention, and consistently produced. There are enough variants htat it can can be hard to recognize even some more standard ones with certainty.

There are perhaps half a dozen common plugs/sockets, and probably at least a dozen or two more variants.

In the image on the right, from top to bottom:

  • 2.5mm TS
  • 3.5mm TS (confusable with audio)
  • 5.0mm barrel (~6.2mm tip) (verify)
  • EIAJ-01 (2.35mm barrel, 0.7mm inner diameter)
  • 3.5mm barrel (1.35mm(verify) inner diameter)
  • EIAJ-02 (4.0mm barrel, 1.7mm inner diameter)
  • 5.5mm barrel, for 1.5mm pin
  • 5.5mm barrel, for 2.5mm pin

Terms, standards, plugs:

  • IEC 60130-10 (:1971) defines five/seven connectors
    • Type A: 5.5 mm outer diameter, 2.1 mm inner diameter (seems the most common?)
    • Type A: 5.5 mm outer diameter, 2.5 mm inner diameter
    • Type B: 6.0 mm outer diameter, 2.1 mm inner diameter
    • Type B: 6.0 mm outer diameter, 2.5 mm inner diameter
    • Type C: 3.8 mm outer diameter, 1.4 mm inner diameter
    • Type D: 6.3 mm outer diameter, 3.1 mm inner diameter
    • Type E: 3.4 mm outer diameter, 1.3 mm inner diameter
  • 'EIAJ connector' usually refers to one of the EIAJ RC-5320A connectors, rather than the other two:
  • EIAJ RC-5320A [16] defines five different thicknesses of barrel pairs rated for 2A. Yellow-tipped DC connectors are likely to be one of these.
note that this is simplified -- these have inner and outer diameter for both plug and socket
  • EIAJ RC5322
    • Barrel type connectors, 6mm outer, 3.1mm inner radius. Pin is 1.0mm
    • wide (6.5mm) plastic tip, apparently to avoid contact in cars and such
    • EIAJ RC-5322

Telling which one you have or need is sometimes be a bit of a challenge.

Small mismatches on the slightly-smaller side tend to be okay, because these are often held by spring contacts.

The common 5.5mm thick DC plug with 2.5mm pin (socket and plug)

For example, my big box of power supplies and wallwarts, 5.5mm-outer barrel connectors is the most common, and seemingly mostly with 2.1mm inner diameter, maybe a few 2.5mm. (I should verify this, but need a pin of known and fairly precise size).

Also, there are a lot of barrels that don't have a solid inside but two (spring?) contacts.

So e.g. a socket made for 5.5mm outer, 2.1mm inner diameter
will likely also accept 4mm 2.1,
and probably 5.5mm 2.5mm.
though a 5.5mm outer, 3.4mm inner may not make contact.

However, a socket with a 2.5mm pin won't accept a 2.1mm inner-diameter.

See also:

3-Pin and 4-Pin DC Plugs

Apparenty KPPX-4P
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Doesn't seem to have any singular standard, name, or pinout.

Everyday names seem to include:

  • snap and lock (though not all variants lock),
  • (incorrectly(verify)) power mini-DIN, power DIN - misleading as this does not mate with any mini-DIN plugs or sockets, because of the thicker pins than DIN, and often larger shell (the ones I saw were ~10mm instead of mini-DIN's 9.5mm)

Often used to deliver two different voltages, and/or more current than basic DC plugs are comfortable with.

There seem to be a bunch of these, most probably unrelated in origin, probably unified more in "seems solid, had has the two/three/four thick-enough pins I need", some of which seem to be are niche standards.

I should probably try to find more of these, but don't count on it.

More specialized

Seen in cars or RC

Cigarette lighter plug
Cigar lighter plug.jpg

Known as cigar(ette) lighter plug, vehicle receptible, and others. Also called a 12V plug, since this is usually what is provided (some exceptions).

Note that there are actually three variations of this plug, with mildly different sizes. Since many have plugs with more than a mm of spring on the side, they tend to be more or less interchangeable, though it's not always the most comfortable fit.

See also:

Vehicle chargers
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)
Type 1 (SAE J1772), Tesla proprietary, Type 2 (Mennekes). Not depicted: Type2

OBD-II connector


SAE connector
SAE connector (and a die for size reference)

Mates with an identical plug. Seen in cars, motorcycles, some batteries, some solar panels, and such.

Meant to be wired so that the exposed lead from the power source may safely touch the car chassis.

See also:

Mostly seen in RC applications

Tamiya connector

Tamiya is regularly seen in RC battery packs. Seems to refer to the plastic's plug/hole shapes (resembles a 2-pin Molex Mini-Fit Jr.) that make this a polarized connection (the square one is positive, the rounded-on-one-side one is ground).

Tamiya seems to be considered a cheapish choice that is good enough for up to a few amps. Or more, depending on the shape and material of the actual connectors(verify).

Also exists in mini variation.

Deans ultra

The Deans Ultra is a polarized connector made to carry serious current for its size (smaller than e.g. Tamiya), largely because of the connector shape.

Flat contacts, one side with springs that push the other side for good contact area.

Rated up to 60A. (but there are some cheap imitations that you don't want to push that high - I recall some rated at 10A(verify))

There is also a smaller micro Deans, rated for a dozen amps.

Powerpole - Anderson PowerPoles (also known as sermos) are rated for ~30A. Can be crimped. Larger than other choices, which makes it easier to pull apart than some other higher-amp choices, and lasting somewhat longer.

See also:

EC3 is a polarized plastic plug (resembling Tamiya) around bullet/banana-style connectors, and rated to approx 60A. They're relatively cheap(verify), so are handy all-round plugs.

People report them being a little easier to separate than Deans. The plastic may deform when things do heat up, though.

There is a less common larger variant called EC5

See also:

Bullet connectors are a solid tube and a solid pin. They may be good for a few dozen or even a hundred amps or so.

Since they are really just two bits of metal, they're probably also the cheapest thing you could call a connector. Of course, without a plug around it (and with some cheap plastic plug designs) you expose metal in ways that easily lets you short things out.

Easily confused with banana plugs. Cheap banana plugs may count on their smallish spring for contact, which means little contact area and so not be good for high currents. Better designed banana connectors may be almost equivalent to bullet plugs.

See also

XT60 is a polarized bullet-based plug rated for ~60A, and uses plastic that deals well with temperature.

There's more variants of this, like XT30 and XT90

See also

Kyosho is comparable to tamiya in rating and also looks similar to it (also resembles EC3 in details).

Also exists in a mini variation.

See also


See also

Unsorted RC-ish power connectors

Mentioned by http://www.flyrc.com/articles/connectors_1.html

Astro Zero loss 2-pin
Astro Zero loss 3-pin
Sermos power poles
Duratrax power poles
Castle Creations 13- AND 16-gauge power poles

Mains power, device side

IEC connectors

Refers to IEC 60320 (IEC 320 before the renumbering), the plug/socket system commonly used on devices which can use various socket-to-device wires.

C1 through C24 are defined, and the male and female versions of a type connector have different numbers. Many are polarized. For a few there are variations (e.g. C7/C8), and some are variants of other IEC plugs (e.g. C17/C18 is unearthed variant of C13/C14).

The most common are probably:

(pairs with C13)
(pairs with C14)
  • C13/C14, commonly associated with PC power supplies, and other devices that may need its moderate current rating (over e.g. C5/C6), including some professional audio equipment.
    • Rated at 10A

  • C19/C20
    • Rated at 16A
    • seen where you may need a bit more current than C13/C14 gives
e.g. computer racks may have C19-to-C14 or C19-to-C20 Power Distribution Units

(pairs with C5)
(pairs with C6)
  • C5/C6, regularly seen in laptop power supplies and other PC-related power supplies.
    • rated for 2.5A

(pairs with C7)
(pairs with C8)
  • C7/C8 (a.k.a. 'figure eight', 'shotgun'), unpolarized, ungrounded, is seen on various lower-power devices, from radios to VCRs, some laptop power supplies, game consoles.
    • rated at 2.5A
    • polarized C7 won't fit into unpolarized C8, which is rarely a problem(verify)
    • unpolarised C7 connectors can be inserted into polarized C8 sockets, but this can sometimes be a bad idea
    • A little larger than C1/C2

  • C1/C2, commonly seen on shavers.
    • Rated at 0.2A
    • Looks like C7/C8 but without the dents that make it figure-8

Variants with higher temperature rating include:

rated for higher temperatures (120°C)
very similar shape to C13/C14, but notched so that only the higher temperature cables are accepted
e.g. used for electric kettles
rated for higher temperatures (155°C)
notched like C15 and blockier on the other side, to be more selective (C15 devices will accept C15A cables as well, but not the other way around)

See also:

Mains power - wire-to-wire connectors

Screw terminals

Screw terminals (with some spade and loop lugs on the bottom one)

Screw terminals terminal blocks, terminal strips and others names are used interchangably, making many somewhat ambiguous.

Not all types are rated for mains voltages, though the ones with separators often are(verify)

Often refer to a screw-and-nut through a flat strip - which are not always the easiest to use on braided wire, and you may prefer to attach forked spade lugs (or loop lugs)

Forked variant of a spade lug (cf. spade connector)

Luster terminals

Luster terminals

Luster terminals, a.k.a. lustre terminals, which seems to come from the german Lüsterklemmen, seem mostly seen around europe.

There are a few local names, like kroonsteen (Dutch), suikertje (Flanders).

Originally porcelain and of larger and simpler design (screw clamping two wires together), intended to be heat isolation. (And you still see ceramic variants of this newer design, e.g. for use around saunas)

Spade connectors

Spade connectors

Spade connectors are a solid bit of metal, and the female part a good amount of area clamping down so these tend to connect very sturdily. (Some also have a clip to make it harder to slide unintentionally)

Various sizes may be rated something between 3 and 24A (order of magnitude).

The female type is frequently shrounded, for isolation.

You see spade connector bars to connect various circuits together in this style.

Related are the eye and fork variants, which are easier to screw down.

Push-in connectors

Push-in connectors.jpg

Push-in style connectors will often push a pushing into spring loaded, sharp construction that tend to dig in a little, and tend to not let you pull out solid core without a bunch of force and/or twisting.

You can often find these rated for something on the order of 24A.

Lever locks

3-terminal WAGO 222

Lever locks clamp a spring down on a wire (varied designs, various of which are smarter than a basic basic pressure plate).

Many are made for wires of sizes like 22AWG to 12AWG, and rated for at least 20A, e.g:

WAGO 222 are spring-clamping connectors rated for 400V/32A (though tests have show they're electrically fine up to perhaps 100A, it's the heating you need to worry about)
WAGO 221 is a smaller variant of the WAGO 222, rated at a very similar 450V/32A (and 600V/20A)

Details are usually listed on them.

Wire-nut, a.k.a. wing nut, twist-on, twister, twist cap connector

Twist connectors.jpg

On circuit currents

Power - wall plugs

The types are a less formal(verify) way of indicating the common plugs to use around the world.


Some of the more common plugs are listed below (lettering system as used by some US document on worldwide power)

Some practical knowledge before traveling: https://www.electricalsafetyfirst.org.uk/guidance/advice-for-you/when-travelling/travel-adaptors/

Type A, Type B, household NEMA variants, JISC C 8303 Class II

(North America, Japan, some other places)

NEMA 1-15 (Type A) plug
NEMA 5-15 (Type B) plug


Type B wall socket
5-20 socket
  • NEMA 1-15 is a 2-prong non-earthed plug, a.k.a. Type A
  • NEMA 5-15 is a 3-prong earthed plug, a.k.a. Type B
  • NEMA mentions about two dozen other variations
most for higher currents, which is why you don't see them in everyday life
some polarized
You may have seen NEMA 5-20
...where the 5-20 plug has one blade horizontal...
...and the 5-20 socket includes a T-shape to accept both the 5-20 plug and 5-15 / 1-15 plugs, mostly in commercial settings where single devices may be designed to draw more than 15A
There are more high-current NEMA plugs, about a dozen in total - but most of them are 20, 30, and 50A which you will only need or see in commercial and industrial settings


The US sockets are polarized - on sockets one slot is wider than the other, and unearthed (2-pin) plug may have one slit wider (that's neutral) than the other (that's hot).

2-pin plugs can then choose to be polarized (make one wrong wider) or not (same size) - though many devices don't care.

3-pin plugs often don't bother with the different sizes, because the presence of the ground pin enforces the polarity.


Some plugs have holes in the prongs. This is not, as commonly believed, designed for more friction, or to slot into anything.

It's for alignment during manufacturing. In fact, NEMA seems to intentionally spec that if they're there, they should specifically be away from the actual mating part of the surface, so that it doesn't reduce contact area. [17]

Type F / Schuko / CEE 7/4


Type F plug
Type F wall socket

Type F plugs/sockets, also known as Schuko (short for Schutzkontakt, roughly meaning 'protective contact', referring to having a contact for protective earth), and formally CEE 7/4, are round sockets/plugs with two earth clips on the side, and two guides for a more robust fit in the embedded socket.

It is used in much of (western) Europe, commonly seen in wall sockets and power strips.

Not polarized, though there is an Argentinian variant that is.

The Russian Gost 7396 looks and is similar, but has thinner prongs, so while you can often plug Gost into Schuko sockets, Schuko plugs often don't fit into Gost sockets(verify).

CEE 7/7 plugs

CEE 7/7 plug

Not a specific country's standard, but worth mentioning because it is designed to work in multiple, in that they are earthed plugs specifically designed to mate with both:

Type F style earth (most of western Europe) and
Type E style earth (France, Belgium, also Poland, Czech Republic, Slovakia, Denmark).

Seen in wires that must be earthed (so can't be europlugs) and meant for wide sales (that is, catching both type E and type F countries with the same plug). One good example is computer power supply cables, which are usually CEE 7/7 to C13.

Other, non-earthed European plugs: Type C, CEE 7/16, CEE 7/17, Europlug

(Type C) CEE 7/17 plug

The CEE 7/17 plug is a something of an unearthed adaptation of 7/16 to mate with Type E, Type F, and round type C sockets.

There is a (fairly rarely seen) socket that accepts no earthed plugs, by being a type E socket but instead of an earth pin, have a plastic pin and a strip of plastic from where it would be all the way to the edge. This seems to be used on 2-wire extension cords, to make sure you can't plug in an earthed appliance and forget that it isn't actually earthed (...and possibly to be legal to sell at all(verify)).

Flat Type C: CEE 7/16, Europlug, also seen at the bottom of a wallwart adapter

Type C exists in round and flat variants.

flat type C, also formalized as CEE 7/16, and regularly called a 'Europlug', is an unearthed plug that fits most European-style sockets (Type C, E, F, others).

Some power strips have a few thin-type-C sockets (and Shuko otherwise), because you'll always have a few devices with these and it saves space in that case (and in that case only, as these sockets accept nothing else).

See also:

Round type C sockets (on an old power strip)
Round type C plug

There is also an unearthed round Type C - socket is CEE 7/1, plug is CEE 7/2.

While the socket (7/1) will accept most any European-style plugs (C, E, F; 7/4, 7/7, others), the round type C plug (7/2) will only really plug into the 7/1 socket, and roughly nothing else - it will not plug into Type E or F sockets (blocked by the plastic that guides the earth).

New installations will use earthed sockets, so the 7/1 socket is barely sold anymore.

Both mean that round type C has become rare both in plug and socket forms (unearthed european plugs are now often europlug or CEE 7/17 (see above), unearthed sockets are just uncommon).

Type E

Type E socket and plug

Seen mostly in France, Belgium, Poland, Czech Republic, Slovakia, Denmark

Looks much like Type C, except for the male ground pin that sticks out.

While it has a fixed orientation, there is no polarization standard. (possibly because that would not apply to other european-style plugs it is fairly compatible with)

CEE 7/7 plug is made to be compatible with E as well as F

Also compatible with others, including (mostly things specifically designed for C, E, and F sockets)

  • 7/7 plugs (european earthed round plugs)
  • 7/17 plugs (the unearthed but still roundish one)
  • and 7/16 plugs (flat unearthed europlug)

Type G, BS 1363 (UK)

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Used in the UK and a dozen other countries[18]

Type G plug and socket
  • Oriented
  • polarized in the standard (though many everyday devices won't care)

Safety features:

  • Earth prong is longer, so a device is earthed before it gets power
  • Sockets may have safety shutters (actuated by the longer earth prong)
  • Newer variants have the non-ground pins half shielded so it's very hard to reach live copper

Other apparent design considerations:

  • All sockets are the same (there is no unearthed socket design)
  • Fuses in the plug - often easier to replace than those in the devices
  • Wire from bottom means people won't often try to pull it out from the wire, so few break that way (though possibly more break unintentionally)

See also:

BS 1363 replaced the earlier BS 546 in the 1940s, 1950s. BS 546 is still in use elsewhere, see Type D, M

There is also a distinct shaver socket, BS 4573, which looks like a thicker variant of europlug.

Type I

Type I plug and sockets

(Australia, New Zeakland, China, Argentina)

Type N

South Africa, and a variant seen in Brazil


Type H

Type J

Switzerland, also seen in Lichtenstein


Type L


Italy mostly sees type L, C, and F


Type K


Phase and neutral distance and pins compatible with Schuko/europlug.

Earth is a half-round pin on the plug,

Danish grounded plugs will only fit into a grounded socket.

However, non-Danish european plugs (type E, type F) plugs will mate, but without connecting ground.



Less-common Danish variants include

  • one pin flat, used in hospitals
  • phase and neutral pins slanted, for computer equipment, though reportedly this is more annoying than it is useful.


Type D, M

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

BS 546 is the older british plug, and also seen in India, Pakistan, some East African countries, South Africa,

Note that these countries may have other plugs. For example, it seems that:

India sees C, D, and M
Pakistan mainly sees C and D
South Africa sees C, D, M, and N

Three round pins.

There are three different plugs, with larger pins spaced further apart, each with their own current rating.

Because of the three distinct sizes, the three varied plugs will only plug into a socket rated for the same current, although there are sockets that take multiple variants.

The 2 A and 5 A plug are considered Type D, the 15 A plug Type M.



Type O

When does wall polarity matter?

Power - industrial and multiphase interconnects


IEC 60309 (Europe)

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

See also:


Edison screw

Edison screw (E27, E14)

Typical for lightbulb/pear shapes.

The number is the outer diameter of the metal screw part in mm.

There's quite a few of them, but by far most common are:

  • E26/E27 - common large screw variant
Apparently there's a correlation where E26 is for 120V countries and E27 for 230V countries(verify),
they're physically close enough to often fit (verify)
  • The more common small variant is usually E14 (Europe) and E17 (US) (verify)

There are a handful of other diameters in use, e.g.

E11 (Europe), E12 (US) 'candelabra'
E10 (miniature) in older flashlights, indicator lights, older bike lights
uncommon now in all those uses, because e.g. LED is more efficient than incandescent
E39/E40 (giant/'mogul') in industrial / older stage lighting

There are also a whole bunch of adapters, because within the same country it's the same voltage, and you might want a different style of lamp, deal with specific or chandeliers, etc.

See also: http://en.wikipedia.org/wiki/Edison_screw#Fittings

bi-post / bi-pin

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Many bi-post are IEC 7004 (verify)

You may like overviews from image searches for terms like light bulb socket types diagram

The number specifies the pin distance. Each distance tends to have a unique socket/plug design, in part to make them more easily identifiable.

GU10 (230V MR16), GX5.3 (12V MR16 bulb)
G9 with its loops

Variants with smaller distances are typically small spots (classically halogen), for example:

  • GU10 - pins, 10mm distance, widened bayonet-style end (seems to be one of only a few G variants that has that bayonet)
  • GX5.3 - pins, 5.33mm distance
  • G4 - pins (4mm distance, thinner)
  • G9 - flat loops, 9mm between the centers of the loops

These may be easy to find in supermarkets and such - though the exact set varies a little with where you live.

Larger variants like

  • G23 and G24 are used in office lighting.
  • G53 is used e.g. in larger PAR spots

On relations to the bulbs

A few further details/associations are specified by the letters, e.g. G, GU, GX, GY, GZ.

For example, GZ bulbs use dichroic glass, which means the glass conducts and dissipates heat, so lets out much of the heat at the back.

Power and beam angle may wel be specified [19] though have some inconsistencies in specification.

While endless combinations between socket, bulb, and voltage could exist, there is a lot of consistency in : what is actually produced at all

what type of bulb, reflector, and voltage is used on each connector

...so in practice most most further details are (only) implied from most specific references being unique(verify).

For example:

  • GU4 are often 12V MR11 bulb
  • GU5.3 are often a 12V MR16 bulb
  • GU10 are often mains-voltage MR16 (as are various others with >7mm pin spacing)
GZ10 is like GU10 but does not have a beveled base, which means you can't use GZ10 in GU10 sockets (but can the other way around). The reason seems to be a heat/safety restriction: GU reduces heat to to the rear/socket, GZ does not.
  • G6.35 (1mm thick pins)
  • GY6.35 (1.25mm thick pins)
  • GY6.35, G8, or G9 are more frequently JCD type.
G9 is often mains, G6.35 is often low-voltage

But don't count on this, because there are exceptions

Shapes and reflectors


Refers to a shape - just the small halogen bulbs, no reflector. Can be 12V, 24V, or mains voltage.

Comes in a few base sockets, often one of G6.35, G4, G8(verify)

Apparenly frequently semi-permeable glass, which is why you shouldn't touch it with your oily fingers.

MR, Multifaceted Reflectors

MR (e.g. in MR11, MR16) refers to a Multifaceted Reflector, which produces a more focused beam than simple parabolic reflectors. (see also PAR, which is more specifically an anodized reflector)

MR bulbs are mostly associated with G-style bases, including GU10, GX5.3, and G4.

The number in MRsomething is the bulb diameter - in eighths of an inch, so MR16 bulbs are 5.1cm in diameter, MR11 are 3.5cm.

The combinations of diameter and socket aren't unique - which means it's fairly easy to walk into a store and buy a MR16 and discover you needed one with a GU10 and GU5.3 base and got the other.

You sometimes see specifications of diameter as well as power and beam angle - see [20].

On voltage

Different MR bulbs may be 12V (most) or higher voltage (some), so never blindly assume.

12V may still be AC, though are often DC in practice.(verify) LED-based MR-series often won't care since they need to rectify anyway.

Some of the 12V (switch-mode) adapters designed for a string of halogen MRs will not like the low power draw of LED variants. You need a transformer that is not trying to be clever, one designed for lower draw, attach more lights on a single adapter, or get one designed with LEDs in mind.

Other notes

See also DIY_optics_notes#Stage_lighting.

See also



This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Exists in a number of variations

  • XLR3, seen as:
    • a balanced audio connector, primarily for microphones (in the past also some equipment interconnections and speakers, including powered ones - now less so, probably due that last bit leading to some pricy mistakes)
    • DMX in a lot of practice
  • XLR4
  • XLR5 - in the DMX specs (while many simpler DMX devices use only XLR3, XLR5 is somewhat common on pricier DMX devices)
  • XLR6

...and various others, some of which are considered obsolete.

The two most recognisable uses are probably in the event industry:

(also note that audio cables and DMX cables, while they look similar, are not interchangeable for other reasons. It'll work on a test-bench scale, but give issues on large scale)

There are also some lesser-seen and specific variants, such as

  • PDN to go between amps and speaker
  • LNE, that carries just mains power, but was apparently never really used

See also:

See also The_XLR_pin_1_problem

Small mic plugs

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)



Used in some professional audio, as a amp-to-speaker interconnection, i.e. already amplified signal.

It seems to have been introduced to be a non-confusable plug, where before you'd have

XLR used both as signal cable and as amplified cable, which could damage things.
TRS that had a similar signal/powered confusion problem (and couldn't deal with as much current, though that doesn't matter for smaller speakers)

See also: http://en.wikipedia.org/wiki/Speakon_connector

Low power or signals

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Sure, there are many things you can abuse the other way, but there are also things that are more designed (or more accidentally quite fit) to carry both low current power, or signals.

Testing things

Banana plugs

Banana plug (4mm) on the black plug on the left (these happen to be stackable).
The thinner (2mm) not-so-banana plug on the right (adapter)

The banana plug is named for the curve that comes from the lengthwise springs that friction-lock the plug.

Actually, shapes vary, and not all 4mm plugs have a friction-lock design, but many do.

Length was typically 20mm, though e.g. the US seems to use 15mm, and there's more variation.

They are rated for something like 30V, 15A. It seems the main reason for the low voltage is not isolation in the arcing sense, but safety in the sense that the thing is entirely exposed.

The ones with fixes shrouds, or sleeves that retract, may be rated for higher voltages.

The 4mm version often carries lowish-current power or occasionally audio - it is seen on things like

  • measuring devices, such as multimeters, bench power supplies, and such
these are often also stackable somehow (4mm hole in the back, or side)
and e.g. banana-to-BNC for oscillosocopes (handy for non-HF frequency measurements)
  • amp/speaker connections
easy to replug
capable of dealing with moderate current

There is a 2mm plug seen in similar situations - seemingly mostly multimeters, probably because it's a nice tradeoff in study enough to not break, and thin enough to poke at many smaller components.

It's not really referred to as a (variation of) banana plug, because the lengthwise springs are not there, but I haven't found a better place to group it under.

See also:

Crocodile clips / Alligator clips

There are many variations in look and quality, these are three of them

Crocodile clips are useful for making a temporary electrical connection that will be decent and stay on.

The ones in the image here are a few cm large and don't carry much current. Two of these plug onto banana plugs, for ease of use with multimeters.

There are large ones, seen e.g. around car batteries, that are much beefier.

See also:

IC clips

Test hooks / pincer clips / IC grabbers

...and probably other names.

Pogo plugs

Mostly used in automated testbeds, where a PCB is pressed into these

Smaller JST connectors

JST refers to a company that makes many series of plugs.

The below are mostly used as PCB (inter)connectors useful for data signalling, though many are rated for (on the order of) 1, 2, or 3A, so also useful to transfer some power.

A few of the series:

JST VH series

Pitch: 3.96mm

keying/mating: thinner on one side, slots to the side, clip

Rated for 10A (with AWG16)

See also:


socket and plug

Pitch: 2.5mm pitch

Pins: 2 (not a series)

keying/mating: round shape that guides into shell

Seen in RC vehicle applications, there known as JST connector, BEC connector, P connector(verify)

Rated for 3A (with 22AWG wire(verify)).

See also:

JST XH series

3, 4, 5, 6, and 7-pin XH sockets on a LiPo balance charger, one 3-pin XH plug

Pitch: 2.5mm

Pins: 2 to 20

Keying/mating: two slits near the side of one long end, with some slight bayonetting (works out more as a friction thing)

Perhaps most recognized as the connector on lithium batteries (verify) (2 or more pins depending on how many cells, for balance charging)

See also:

JST PH series

9-pin male PH-series connector
Plugged 2-pin PH-series connector

Pitch: 2.0mm pitch

Pins: 2 to 16

Keying/mating: socket has part of one side open, plug has slits keying for that side

See also:

JST EH series

2.5mm pitch, pairs with one unshrouded side

Pins: 2 to 15

Keying/mating: socket one side open, plug one side wider; slits on short edges

See also:

JST SM series

2.5mm pitch

Pins: 2 to 18

Keying/mating: locking clip and keying on middle of one long side

"SM2 connectors" seem to refer to the 2-pin variant(verify)

See also:

JST ZH series

Pitch: 1.5mm

Pins: 2 to 13

Keying/mating: two slits on the sides (the shortest ends)

See also:

JST SH series

Pitch: 1.0mm

Pins: 2 to 20

Keying/mating: slits on side(verify)

See also:

Smaller molex connectors

Molex KK

5-pin Molex KK-254(verify)

Pitch: 2.54mm Pins: 2 .. 36 Keying/mating: slits around socket's wall, ridge along wall for friction

Pitch: 3.96mm Pins: 2 .. 24

Pitch: 5.08mm Pins: 2 .. 12

See also:

Micro and pico variants


  • picoblade
1.25mm pitch
molex picoblade

Smaller AMP connectors

(The company is now TE Connectivity, previously Tyco Electronics, and AMP far before that, but we tend to still call them connectors AMP)


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

MTA 100 connector

single row, 0.1" / 2.54mm pitch

MTA 156 connector

single row, 0.156" / 3.96mm pitch

mta-156 OR MTA-100


Circular metric

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Circular metric and circular industrial seem to be informal names that broadly group connectors that are fastened with a (metric) screw barrel.

I can find no standards yet, but can find a lot of variations, so it seems to be a basic idea implemented in different ways by various companies.

...which is probably why there are also snap-in, bayonet, push-pull variants, various types of keying, and more variations.

In my recollection (very biased) I've seen the metal variants more around larger and industrial machines, probably because they're a study way to have many-pin control signal interconnections.

And there's e.g. the GX series connectors mainly seen around aviation, usually smaller and fewer pin (I see mention of GX16, GX20, GX12, the number is the barrel diameter in mm)

....down to some cheap plastic (but waterproof) connectors seend around garden lighting and christmas lighting, distinctly keyed (which in a few examples I found correlated with the voltages used).

...and apparently everything inbetween.

Grove connector

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

The grove connector is defined by seeed studio.

It's a 4-pin, 2mm-pitch connector (not a JST or moxel plug, apparently NSTech PITCH 1125?)

They're basically a specific standard pinout to make quick prototyping easier.

Pinout seems to be

  • VCC (5V or 3.3V depending on context)
  • Gnd
  • Sig1
  • Sig2

...where the signal pins may be wired one of

  • digital IO - two adjacent digital pins
  • analog IO - two adjacent analog pins
  • UART - RX, TX
  • I2C - SCL, SDA
  • no SPI?(verify)

It's not a universal connector, it that each grove socket is wired to just one of these, and you still want to think about what the device behind this is capable of.

Also e.g. consider that digital pins may overlap with UART or may be PWM capable.

See also:

Mounts, chip carriers, packages, board connectors

Mounts, chip carriers

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Packages refer to the specific design and size of something a particular component is housed in.

You will often see specific component types (and particularly specific models) in certain specific packages/mounts. For example, transistors are often seen in SOT or TO, diodes often in DO, LEDs often in what seems to be called T1, and so on.

Surface mount which may seem recent but has been around since the sixties. Surface mount has introduced a lot of specific smaller packages. It's hard to summarize them and give a decent impression of which are more common.

On pitch

Pitch refers to the spacing of pins (more often mentioned in through-hole components, as those are fairly wide-purpose, while suface mount components tend to be more specialized packages)

Common pitches include

  • 2.54mm (0.100")
  • 2mm (0.079")
  • 1.27mm (0.050")
  • 0.8mm (0.031")
  • 0.5mm (0.019")

There are a number of different measures that can be relevant in addition to pitch.

See for example http://en.wikipedia.org/wiki/List_of_electronics_package_dimensions#Through_hole_pin_dimension_reference

SMD/SMT versus though-hole

There is a noticable distinction in through-hole versus surface mount:

SMD (Surface Mount Devices) and SMT (Surface Mount Technology) often means leads that end flat on the circuit board, to be soldered in place (often with reflow soldering, wave soldering, or such).

SMD seems to have become popular since approximately the eighties. There are SMT variants of ICs, resistors, capacitors, and various other sorts of packages.

SMD/SMT can also be seen as the top of a hierarchy of a load of specific packages.

The style it is replacing has been (retroactively) named though-hole, occasionally abbreviated to THT (though-hole technology).

See also:

Packages, roughly from fewer to more leads

TO, SOT, SC, some small SMD

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

TO, SOT, SC, SOD refer to a style of making packages, all with quite a few variants, and usually with a small pin-count (often between 2 and perhaps 7, usually between 3 and 6).

While they have names referring to specific uses and sizes (TO: 'transistor outline', SOT: 'small-outline transistor', SOD: 'smal outlide diode'), most of these packages end up seeing many other uses - particularly those packages that handle more than average power (heat).

Note that a number of specific packages have names in more than one of these series.

Many of these are THT, some SMT, some usable as both as they have long pins (some bending involved for THT).

TO ('transistor outline')

TO is often used when there is power involved (mostly because of the package's thermal capacity), e.g. for transistors, regulators, darlingtons, power resistors.


Specific TO packages include:

  • TO-220 (images) (good heat dissipation, frequently used where power is involved)

  • TO-236-AA (resembles SOT-23, but sizes are a little different)

  • TO-252(-AA), a.k.a. DPAK (4.6mm pitch)
  • TO-263(-AB), a.k.a. D2PAK (effectively 5.08mm pitch, because the middle isn't a pin(verify))
  • TO-262 a.k.a. I2PAK
  • TO-251 a.k.a. IPAK

SOT-23 with 3 pins

SOT ('Small Outline Transistor')

A surface-mount package, used for transistors, but also rectifiers, regulators, and more.

There are quite a few variations, many with pins that are wider for better heat transfer.

  • SOT-23 - with different amounts of acually present pins, sometimes referred to as:
    • SOT-23-3
    • SOT-23-5
    • SOT-23-6
    • SOT-23-8
  • SOT-89
  • SOT-223 (three-terminal)
  • SOT-232 (three-terminal)
  • SOT-363
  • SOT-353
  • SOT-416 (SC-75) (three-terminal)
  • SOT-723 (three-terminal)
  • SOT-883 (three-terminal)

SC looks like SOT, but has thinner leads (verify)

  • SC59
    • SC59-5
    • SC59-6
  • SC-74A
  • SC-70


THT-style diodes are often seen in DO-xx, for example

  • DO-35
  • DO-15
  • DO-41


LEDs often in [21]

  • the circular plastic housing is often mentioned just by its radius, though seems to also be called:(verify)
    • T-1 (3mm)
    • T-1 3/4 (5mm)
    • T-3/4 (2mm)

seems to be called T1(verify) (but more commonly mentioned just by its radius)

  • flat housings (THT connectors)
  • SMT


You can use pin headers as SIP package

Pitch: 2.54mm

Single Inline Package. Regularly 0.1" pitch. Hardly a package at all.


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 2.54mm (most variants)

16-pin DIP socket; 14-, 6-, and 4-pin DIP ICs
(all 0.3" row spacing)
DIP-24 with 0.3" row spacing
DIP-24 with with 0.6" row spacing

DIP (also DIL): dual in-line package, usually for ICs which need relatively few pins (up to 64 or so, usually fewer).

DIP often implies 0.1 inch (2.54 mm) pitch.

Most DIP chips have a row spacing of either 0.3 inch (7.62 mm) or 0.6 inch (15.24 mm). DIP is now often assumed to be 0.3" (which is also sometimes called skinny DIP(verify)).

Since DIP is largely about pin spacing, many things besides ICs can use or be compatible with DIP, or make DIP sockets useful for other things than DIP ICs.

For example:


SOIC (Small-Outline Integrated Circuit)
This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 1.27mm

Pin count variation:

  • SOIC-8
  • SOIC-14
  • SOIC-16

There are wider variants.

See also:

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 1.27mm (verify)

SOIC with J-type leads (instead of gull-wing leads).

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 1.27mm, and also 0.80mm, 0.65mm, 0.5mm, 0.4mm

Followed SOIC(verify)

  • TSOP (Thin Small Outline Package) [22]
pitch: 0.5, 0.55, 0.65, 0.8, 1.27mm
  • SSOP (Shrink Small Outline package) [23]
pitch: 1.27mm (verify)
  • TSSOP (Thin Shrink Small Outline Package) [24]
Pitch: 0.65mm
  • VSOP (Very Small Outline Package) [25]
0.65 mm
  • MSOP (mini SOP)
Pitch: 0.65mm
  • QSOP (Quarter size SOP) [26]
Pitch: 0.625mm (25 mils), usually
  • µSOP (micro SOP)
Pitch: 0.5mm
  • HSOP - SOP with heat wings
  • HSSOP - SSOP with heat wings
  • CSOP

PLCC (Plastic Leaded Chip Carrier)

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 1.27mm

Micro Leadframe, Flat No-lead

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 0.8mm, 0.65mm, 0.5mm, 0.4mm, 0.3mm


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 2.5mm, 1.27mm

Plastic or ceramic (PPGA, CPGA)


This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Pitch: 1.5mm, 1.27mm, 1.00mm, 0.8mm, 0.5mm

See also

Unsorted chip mounts

PCB connectors

('PCB connectors' is probably not the best name, I'll think of another)


Basic pin headers (male), here on the back of a small PCB

Known variably as pin headers, just headers, as breakaway headers, as and under various other names.

Often 2.54mm (0.1") pitch.

Also the things that jumpers (sometimes known as shunts) sit on.

And you could call a row of headers a Single In-Line package (SIP) without too much of a stretch.

PCB headers are a fuzzy, wider concept, and can refer to pin headers as well as many more specific deivations, then often seen in shrouded and/or keyed (notched) form.

One simpler example is KK-family molex, which mostly add bits of plastic as polarity protection but will fit on basic headers as long as they have the same pitch.

PCB mount screw terminals

PCB Screw terminal.jpg

Screw terminals in general may be little more than screw to fasten down a wire to a metal plate.

The variant for PCBs, with pins you can solder, is usually also shrouded.

See also:



Euroblock, also known as Phoenix connector, has screw terminals on one side and a snap-in connector on the other.

It can be convenient and fast working on semi-permanent setups.

It seems mainly used around few-wire control signals (e.g. RS-485) and audio setups.


DIN 41651

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

DIN 41651 (image search) includes various series of fairly common insulation-displacement connectors, including IDC.

Usually two-by-many pins, also seen in four-by-many.

Often 2.54mm (0.1") pitch, smaller variants exist.


  • With or without alignment notch (verify)
  • With or without strain relief
  • With or without latches

DIN 41612 / IEC 60603-2

"DIN 41612" OR "IEC+60603-2" (image search) resembles DIN 41651 (IDC and such), but applications are more specialized, and often has more connections (dozens is not unusual, up to over a hundred).

Commonly two-by-many or three-by-many pins.

Used by some pluggable rack systems, e.g. VMEbus, which is why a lot of image hits will be the 3x32 variant.

See also:

Flexible flat cable (FFC)

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

File:Flexible Flat cable variants.jpg

Could refer to any cable that is flat and flexible, but FFC usually refers to a fairly specific type commonly seen used as pluggable interconnects in tight spaces such as laptops, phones, printers.

Seen in various colors - transparent brown, gray, black, white, and others (color can correlate somewhat with size/pitch).

Common pitches include 0.5mm, 1 mm, 1.25mm, 2 mm. Thinner than ribbon cable.

FFC connectors often refer to the PCB sockets that accept the end of these cables, although complex designs may opt for specific connectors that take less space.

Related are Flexible Printed Circuits, which are circuits built fairly directly onto these cables (often using small SMD components, and often fairly simple circuits).

See also:

(Card) Edge Connectors

back of a 5.25" floppy drive with a card edge connector, notched to match the connector on the bottom

Refers to connections where one side is part of the PCB itself, with traces going to the edge in regular spacing, meant to plug into a spring connector socket,

That socket is often either fixed on a PCB (consider RAM, PCIx and similar), or sometimes in the middle of a cable (consider 5.25" floppy drive connectors)

Consider e.g.

  • various buses for expansion cards (ISO, PCI, AGP, PCIx, etc.)
  • various game ROM cartridges (NES [27], Sega[28], N64[29], etc.), Gameboy, DS, Switch
    • some gray area -- many memory cards do not technically qualify - they look the same as these cartridges, except that the contacts are often not traces on a PCB
  • 5.25" floppy drives (two-sided, 34-pin)
  • RAM modules (rather smaller pitch)

A lot of these are two-sided, but simpler cases are not

See also:

Board-to-Board connectors

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Broadly refers to anything that does many-channel signaling between distinct circuit boards.

Can refer to

  • setups that directly fit boards together (often fairly specialized, small, pin-dense connectors)
  • things only useful for board connectors, like FFC
  • wire-to-board used to connect boards, like IDC

Specific physical layouts like Arduino shields, mikroBUS