Difference between revisions of "Common symbols around you"

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m (Uses, safety)
m (Uses, safety)
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File:mounting material.png|three variants of "safe to mount on 'normally flammable' materials", e.g. wood
File:mounting material.png|three variants of "safe to mount on 'normally flammable' materials", e.g. wood
File:ESD.png|electrostatic discharge protection required
File:ESD.png|electrostatic discharge protection required
<gallery heights=40px>
File:FCC.png|Meets FCC's EM emission standards
File:FCC.png|Meets FCC's EM emission standards

Revision as of 20:22, 9 November 2019

Uses, safety

Some mark mentioning RoHS means it's compliant to RoHS

Power supply

basic DC adapter specs

The top symbol is for DC barrel plugs, specifying whether the inside or outside is positive.

The middle line is input, where the squiggly tilde ~ indicates AC, here mentioning an input voltage range and frequency it's okay with (these specs amount to worldwide use).

The third line (output)'s solid and dotted line indicates DC.

LPS (Limited Power Source) have relatively low maximum voltage, current, and power. [2]

SELV (Safety Extra Low Voltage), where the power supply output stays safe under single fault conditions. [3]

Transformer (general)

isolating, safety isolating;    non-short-circuit proof, short-circuit proof

separating transformer, output >1kV, variable, constant voltage, perturbation attenuating

Double circle, like a vertical venn diagram, are transformers, with a handful of properties marked. There are more combinations of all the parts this image shows, and further ones (e.g. construction site).


Some of the more commonly seen logos / certification bodies include:

Bunch on european certifications

There are also many testing centers, that may deal with additional health and/or safety and/or environmental concerns, though in most cases it's just country-specific.

You're probably used to the logos for the ones applying to your part of the world.

Certification marks, in the end, represent agreements between manufacturers and (ideally well known) testing centers. (and note there are logos that do not mean that at all)

In most places these are not strictly required for sale(verify), yet certification is quite common for a collection of reasons, like you caring about your safety, for company insurance (liabilitywise), varied indirect regulation (e.g. electrical code, fire regulation, medical safety) effectively only buying certified devices, or self-imposed regulation like caring that your house doesn't burn down and for related insurance.

For some devices (e.g. separate power supplies) you can see more-than-usual certification marks, for practical reasons: e.g. when a large company that has locked down the design so that they can mass produce it, for worldwide sale, without a lot of new certification (certifcation is slow, sort of expensive, and may need periodic recertification).

CE Mark and Chinese Export
There are also a bunch of fake symbols.

Best known among them is the "chinese export", a nickname of chinese producers stamping the european CE mark. Often with different, tighter spacing to have the argument it's not the same (note some real CE products sometimes do this too for spacing reasons).


A bunch of markings used around mechanisms, indicators, and buttons, around cars, audio, production lines are settled in ISO 7000 / IEC 60417, see e.g. See https://www.iso.org/obp/ui#iso:pub:PUB400008:en

IP ratings for water and object safety

clothing / washing labels

Packaging symbols




Single use, keep dry, don't use if package damaged