Monday, November 26, 2012

Apple #612: Power Symbol

Welcome back from Thanksgiving, everyone.  I hope you all had a delicious holiday.  In the meantime, I've had a request!  Regular Daily Apple reader Johansen asks:

This may be tiny and not interesting but I'd like to know who invented
the little power symbol that's pretty common on computers. You know
the circle with the line sticking out of the top? I think I've seen it
on multiple devices so it seems like it's not patent protected.

Since tomorrow is Cyber Monday, the Monday after Thanksgiving when everybody apparently starts doing their online shopping for Christmas, this does seem to be an appropriate topic.

The universally used and recognized Power button. But what does it really mean?
(Image by Vova Devyatkin at Freebiesbug)

  • Johansen, I think you wanted a nice easy answer, like "Joe-Bob Computer came up with the insignia when he was 12 and playing games on his Atari."  But no.  It didn't happen like that. 
  • Or at least, if one person did have the idea to use that symbol, his or her name has been lost to the sands of time or else buried under the paperwork of international technical standards.


The International Electrochemical Commission

  • When people talk about this Power symbol, they refer to a technical standards committee called the IEC as the body that first officially registered the symbol. 
  • The IEC is the International Electrochemical Commission. It's made up of tens of thousands of individuals, companies, and academics from around the world who know all sorts of stuff about electric and electronic products and services.  They work together to decide how products in this industry should be standardized.  
  • This group makes sure that our electric and computer products will work the same from country to country, and that parts made in one country will work with equipment made in another country. So they set standards and codes and establish symbols that everybody will use so that everybody in the industry is speaking the same language.
  • So, once upon a time, back in 1973, somebody or some group of people in the IEC decided what the Power symbol should look like. 
  • Their decision was probably based on products that had already been made or were being used at the time.  So most likely, somebody else came up with the symbol before the IEC did, and the IEC only codified it.  But the only record we have now is the IEC's codification.

The Symbol
  • The IEC actually codified a bunch of symbols related to On and Off at the same time. But which symbols people have used have changed as the technology has changed.  I'll take you through a chronology of On/Off switches to show you what I mean.
  • First there was Power Off/Power On, where you slid a switch from Off to On.

(Photo from Commonsense Design)

  • Then there were what's called rocker switches, where one switch toggles between off and on, but instead of using the words, they used the symbols. In the binary world of computers where everything is either a 1 or a 0, the IEC decided that 1 is On and 0 is Off.  Except they used a sans serif 1, which looks like a straight line.

(Photo from Commonsense Design)

  • When the button was changed from a rocker switch, computer manufacturers were more sophisticated in how they were making their equipment in other ways, too, so that when you powered the thing down, you weren't necessarily completely cutting the thing off from the main power supply.  So the power switches started to use the On / Standby symbols, where Standby is a circle with the straight line through it: a combination of Off and On.

(Photo from Commonsense Design)

  • But then the power switch went to just plain Standby. Which we then interpreted to mean On.  Or Off.

The current, ubiquitous Power symbol on an iPhone case.
(Photo and iPhone case from Zazzle)

  • What's weird is, we general public folks universally interpret this symbol to mean On/Off.  But what it technically means is Standby only.  

People love the Power button so much, you can buy everything from T-shirts to cufflinks labeled with the symbol.
(Photo and T-shirt for $10-$19 from Think Geek)

  • A true single-push On/Off button would be a straight line in the middle of the circle.

The true On/Off symbol
(Image from Designosophy, which misunderstands the symbols)

A true On/Off button.
(Photo from

  • But our current favorite Power Symbol (which is really the symbol for Standby) has actually become a bit of a hot topic in the industry.  Since we have started to interpret the old Standby symbol as On/Off, and since the industry is becoming increasingly interested in finding ways for these gizmos to conserve power, there is a renewed interest in putting these devices into a true Standby mode.  So they've recently come up with a new symbol, the crescent moon, which will now be used as the new Standby (a.k.a. Sleep) symbol.

A lot of Sleep buttons have the word Sleep written beneath them. So it seems the crescent-shaped Sleep symbol hasn't quite caught on. 
(Photo from Sharky Extreme)

  • Unlike our favorite On/Off (actually Standby) symbol, the Sleep symbol doesn't really have the streamlined, to-the-point, high-tech feel about it, though. It's also too easy for different manufacturers to make the Sleep symbol look different from each other. Maybe the IEC and other technical people should have consulted with some designers before they came up with the crescent.

You can even get a ring that looks like a Power symbol (which is really a Standby symbol).  That's just not happening with Sleep.
(Photo of ring and more Power symbol stuff from Mashable Tech)

DOE Lawrence Berkeley National Laboratory, The Power Control User Interface Standard, December 2002, The Meaning and Design Behind "On" and "Off"
Commonsense Design, The evolution of the On/Off power switch symbol, May 7, 2008
Lawrence Berkeley National Laboratory, ISO/IEC/JTC1 Graphical Symbols for Office Equipment
IEEE 1621 Power Control User Interface Standard Appendix V - Standards Related to Power Controls, December 2002


  1. Hmm... perhaps that Standby ring would be a good gift for someone with whom you make one of those "If neither of us is married in ten years" pacts.

  2. That's at once a very good idea and a very sad one.


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