⏻

Description
The power button or standby symbol: a half-circle with a vertical line protruding outwards cutting through the top-centre of the circle, and ending in the circle's centre.

Origin
Created 1973 by the as a translingual symbol for electronic products intended to be shipped around the world; likely an alteration of, itself a combination of  and.

Symbol

 * 1)   sleep mode.
 * 2)  Login; logout.