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I know I (line) and O (circle) symbols are used to specify a switch that turn on and off the power supply.

My question is What is its origin?

Because I thought that it represent a power line that can be plugged (on symbol) and a closed line (and thus without power supply) but seen that in Wikipedia said that it can come from 1 and 0 used in binary to represent on and off bits, I don't know what is the correct answer.

Note: In Wikipedia, it didn't have verified sources, so I need other source.

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  • \$\begingroup\$ I would love to think of the circle as a continuous loop and the I as an open circuit (straight line) but apparently the IEC has decided otherwise. \$\endgroup\$ – Mister Mystère Apr 11 '15 at 11:04
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I'm pretty sure it comes from the binary 1 (on) and 0 (off)

It's an IEC standard symbol, the on symbol is IEC-5007 and the off symbol is IEC-5008

The full standard document they come from is IEC 60417, which you have to pay for, but here is a small reference document with just the power symbols reproduced.

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  • \$\begingroup\$ You know if in the full standard document appear what is its origin? \$\endgroup\$ – PhoneixS Oct 11 '12 at 10:13
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    \$\begingroup\$ No sorry I don't - I think your best bet might be to contact the IEC directly if you need a definite answer for the origin. \$\endgroup\$ – Oli Glaser Oct 11 '12 at 15:40
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    \$\begingroup\$ Ok I have make contact with secretary of IEC and he confirm that come from logic 1 and 0.Here is he response "Dear Mr Alfonso, Thank you very much for your mail of 13th Oct. They are believed to standardized from logic 1 and 0. Best regards, Yoshikazu Seki, Secretary of IEC/TC 3/SC 3C" \$\endgroup\$ – PhoneixS Oct 14 '12 at 10:43
  • \$\begingroup\$ @PhoneixS - good work, thanks for letting me know the result. \$\endgroup\$ – Oli Glaser Oct 14 '12 at 17:46
  • \$\begingroup\$ @OliGlaser You should include the content of PhoneixS's comment in the answer. \$\endgroup\$ – Paul A. Clayton Feb 6 '14 at 22:52
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I never understood the symbols to be representative of binary 0 and 1, just that the circle disconnected the circuit and prevented current flow and the line allowed current flow.

enter image description here

I'm not sure I believe these symbols are representative of binary numbers. Yes, they are an IEC standard, but how the IEC came up with these symbols still seems to be a mystery, and I wasn't able to pull up any sources with a cursory Google search.

Using binary doesn't make sense to me personally - 0 in binary is not defined as "off", its just 0. You can have active low signals that are binary 0 but considered "on".

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    \$\begingroup\$ I disagree. In SOP form of Boolean logic and binary systems in general, 0 is defined as "OFF", "LOW", "FALSE", etc. while 1 would be "ON", "HIGH", "TRUE". To consider 0 "ON" you would be talking about the duality which would be POS. I'm a bit rusty but google 'Canonical form'. \$\endgroup\$ – Analog Arsonist Oct 11 '12 at 16:50
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Binary uses 1's and 0's for on's and off's to represent the switches that would be on and off in mechanical relay systems. the power switch symbol with the 1 and 0 overlay-ed indicate a toggle switch as opposed to a rocker switch that would have the 1 and 0 separated.

EDIT: http://energy.lbl.gov/controls/overview/docs/symbols1.pdf

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  • \$\begingroup\$ Thank you for the answer, but have you a source of it becoming a standard for this reason or is a "de facto" standard origin? \$\endgroup\$ – PhoneixS Oct 10 '12 at 15:50
  • \$\begingroup\$ @PhoneixS See the edit \$\endgroup\$ – Jeremy Oct 10 '12 at 17:15
  • \$\begingroup\$ It explain the meaning of the symbol but not its origin. \$\endgroup\$ – PhoneixS Oct 11 '12 at 10:10
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The origin of the word "On" in itself is a marvel Osiris was the light referred to as "On" in prayer in the land of Khemet where the science of Alchemy originates. As most of the original inventors of the modern age where practicing alchemists or initiates I would search for answers there. Look for corresponding alchemical symbols and early electrical ones.

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    \$\begingroup\$ While I've got no particular reason to disbelieve your explanation it would be good to back it up with a few references. \$\endgroup\$ – PeterJ Dec 10 '13 at 8:47
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A Certified Master electrician I know first explained this to me years ago. According to him the off symbol "0" represents an uninterrupted electrical circuit (circle), that has electricity traveling from the power source through the wiring in a continuous loop

Once a device's switch is turned on the electrical current flows, more or less, from the power source to the device in a straight line; which explains the "1" symbol. Actually, more often than not, the symbol used is..."l"

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  • \$\begingroup\$ Not even wrong. \$\endgroup\$ – Marshall Eubanks May 20 '15 at 3:35
  • \$\begingroup\$ Would an uninterrupted electrical circuit not actually be called s short-circuit? I'm not an electrician, but I doubt a short-circuit would represent a switch set off which actually leads to an interrupted circuit. \$\endgroup\$ – not2savvy Jun 28 '19 at 13:45

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