Wednesday, April 25, 2012

Power Off and Standby Switch Symbols

New Scientist's Feedback column for 21 March 2012 features an item on many devices consuming power when supposedly turned "off". The article suggests having a requirement that "off really means off". But this is already the case. There are two different international standard symbols for a power switch. The one for a true on/off switch has a circle with a vertical stoke in it. This is the IEC 5010 power on-off symbol: the circle represents the number zero and the stroke the number one, the switch representing the binary status of the switch: on or off.
on/off switch symbolA device with a standby state has a broken circle, with the vertical stroke through the break, indicating that the device is never truly off (IEC 5009 standby symbol).

Many power saving initiatives incorrectly use the standby symbol as the logo of their campaign, when they should use the true on/off switch if they really want to save power.

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