Difference between revisions of "Common symbols around you"
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Revision as of 18:17, 20 December 2019
double insulated, a.k.a. Class II
Class III (low voltage device, probably with SELV supply)
"Independent lighting auxiliary"  roughly meaning "lighting power supply not built into the luminaire"
three variants of "safe to mount on normally flammable materials" (meaning things like wood and fabric(verify))
Some mark mentioning RoHS means it's compliant to RoHS
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. 
SELV (Safety Extra Low Voltage), where the power supply output stays safe under single fault conditions. 
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:
UL (United States)
BSI, also Kitemark (UK)
TÜV (Germany, international)
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).
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