Power On/Off: Symbology Explained

Q: All my electronics and gadgets have variations of little circles and lines on the power switch. How do I tell which is actually ON and which is OFF?

A: To be honest I never knew which direction was ON or OFF until this question was recently asked. I simply flipped the switch in the other direction without much thought. Whether it’s a toggle or a single push button, the little symbols on the buttons actually have meaning behind them that visually define what that button is supposed to do. A quick peek at Wikipedia (and double checked through the listed sources), The International Electrotechnical Commission (IEC) is the group behind the standard that provides the following definitions:

IEC 5007, the power on (line) symbol, appearing on a button or one end of a toggle switch indicates that the control places the equipment into a fully powered state. It comes from the binary system (1 or | means on)

IEC 5008, the power off (circle) symbol on a button or toggle, indicates that using the control will disconnect power to the device. It comes from the binary system (0 means off)

IEC 5010, the power on-off symbol (line within a circle), is used on buttons that switch a device between on and fully off states.
IEC 5009, the standby symbol (line partially within a broken circle), indicates a sleep mode or low power state.

The switch does not fully disconnect the device from its power supply. This may appear on a toggle switch opposite a power on symbol, alone on a pushbutton that places the device into a standby state, or alone on a button that switches between on and standby.

A crescent moon, indicating sleep, is added by IEEE 1621 as a replacement for the standby symbol.

Now we know the difference between all the buttons and symbols other than just ON or OFF.

(Images: Flickr member F Delventhal licensed for use under Creative Commons)