Sleep symbol

How to read it

The crescent moon is the sleep symbol of IEEE 1621, the standard for power controls on office and consumer electronics. It is not in IEC 60417; Lawrence Berkeley National Laboratory proposed it in 2002, in the work that became IEEE 1621. The draft standard defines sleep as a power state with more power use, capability and responsiveness than off and less than on, and uses the symbol on a sleep button or with a sleep indicator. Unicode encodes it as U+23FE, the power sleep symbol.

Also searched as: sleep mode.

Three power states

The 2002 report proposed limiting devices to three power states, on, sleep and off, with green lights for on and amber for sleep. When IEEE published the standard, a 2005 report from the American Institute of Physics described it the same way: three states, a circle broken by a line for the power switch, and a crescent moon for sleep. The authors kept the moon as a separate proposal from changing the meaning of the Power symbol, because a new sleep symbol did not undermine the older symbols and should not be controversial.

The crescent and Islam

The Lawrence Berkeley team looked at whether a crescent moon would be read as a religious sign. It was the only cultural question that became a major concern in their work, and they concluded it was not a problem if a few guidelines kept the crescent from looking like the Islamic one. The 2014 Unicode proposal notes that IEEE 1621 meant the symbol to be different from the other crescent moons in Unicode, and Unicode gives it a character of its own, apart from its crescent moons.

Differences by country

Gizmodo reported in 2010 that the crescent moon had become the usual sleep symbol on devices in the US and Europe, while in Japan a “Zzzz” button was sometimes used instead.