What is the origin of on and off power switch symbol?

We all know the symbol with a vertical line in a circle: it identifies the On/Off power switch. It occurred to me that this familiar symbol is evolving in a bizarre fashion.

Originally, switches had a lever or slider that could move to either of two physical positions. In those days the switch was marked with the word POWER and its positions with ON and OFF. Then, as

switches became smaller and more globalized, the two words were replaced with 1 and 0, as seen even today on many rocker switches.

And then the ubiquity of microprocessors made it more economic to do everything with momentary push button switches; the computer inside could take care of figuring whether you meant ON or OFF. And so, the button now needed an icon that conveys both options; I surmise that is when the familiar “1-inside-a-0” symbol came into existence (if you know otherwise do share in the comments!) This round icon fit nicely on round buttons, and became ubiquitous.

But then we start to see the form shown in the two photos above right: a bastardized version combining the 1-in-a-circle with a 1 in the same symbol. This makes no sense at all – the correct representation would have been 1/0, for On slash Off. Instead we get On slash OnOff. Sloppy thinking…

Such erroneous contractions are often seen in spoken language – as in “IT technology”, which expands to “information technology technology” (there’s even a company by that name, and its slogan, amusingly, is “We make sense of IT“). But now we see the same error invading the more compact space of visual symbols…

Source: Commonsense Design

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