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If you do a quick image search on your favorite search engine on "light switch" you get a large number of images. Most of them have up and down direction, to represent state. Up for on in the US, and down for off. This varies among countries and as an example UK, Ireland, Australia and New Zealand have it the other way around.[1]

More advanced light switches operate in pair such as in stairs, where the direction gets out of sync. Then the original meaning of up is lost altogether. A better way would be to have a toggle button instead. Cultural differences and stairway switches would be easier to operate, with a toggle button.

There is probably a good reason for the directional button, thus the question:

Why do light switch buttons have up/down direction when it's really a toggle function?

Light Switch with direction

[1] Light Switch - Up or Down

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It's just how physical switches exist, they're switches, not inset buttons. I don't know historically, but "toggle" is pretty difficult to show at a glance physically without a direction. Also note that iOS uses toggle switches that are "left and right" simply because it's easy to differentiate states. Light switches have problems because they're not standardized. – Ben Brocka Mar 23 '12 at 13:11
I'm quite certain that the light switch looks and acts the way it does because of the mechanical requirements. Creating a button with a toggle affordance with the same durability and dependability as the switch would probably have been hard back in the days. – AndroidHustle Mar 23 '12 at 13:36
@AndroidHustle I mean states of the switch of course. Not all "light" switches activate lights or have an immediately visible stimulus when "on" – Ben Brocka Mar 23 '12 at 13:52
@BenBrocka it was a joke... =\ – AndroidHustle Mar 23 '12 at 14:00
@BenBrocka. Or, in the case of my parents' house, there's a light switch in the kitchen which controls a light in the back yard. The kitchen is in the front of the house. – TRiG May 1 '13 at 17:49
up vote 13 down vote accepted

The simple answer is that switches are meant for toggling functions. What else are they for? The switch we use for lights in the US is called a toggle switch.

Toggling buttons wouldn’t be too bad of an alternative. They are good mostly for situations when the on and off physical position are ambiguous, such as on aircraft overhead panels, or with a population of international users, as you suggest (assuming an In position means an On state in all relevant countries; I don’t know). FWIW, in the US, we still label our switch positions “On” and “Off,” not that it helps much in the dark.

Toggle (or rocker or slide) switches are generally preferred to toggling buttons because there is a distinct action that distinguishes an On command from an Off command (plus the clearer visual difference that Ben Brocka mentions in his comment). Imagine this scenario: enter a dark room and, by feel, stab the toggle button. Nothing happens. So you stab it again (maybe it didn’t quite take). And maybe again. Still nothing. Now you remember it’s a cranky old fluorescent light that takes a few seconds to come on. Now what? Is the light set to go on or off? Maybe the light was set to be on before you got there but the light has finally burned out. How long do you wait? You feel the button and try to guess if it’s set to be On. Toggling buttons in my house are out-dented whether on or off; they’re just out-dented more when off (I think they do it that way so it’s easy to turn it off with a panicked swat, like when something catches fire). Is your button in enough?

The stairway switch issue (a three-way switch) is certainly a known human factors problem, but it’s purely an artifact of the cheap and simple mechanism used (I wouldn’t call it “advanced” at all –we’re talking 19th century technology). A toggling button would have the same problem. The solution would involve putting a solenoid in the switches at each end of the stairs so their positions stay in synch. I sense a business opportunity for marketing to high-end light switch users.

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Having the actuators move physically to stay in sync is difficult. I have, however, seen a system which used switches that were spring loaded to a center-off position; pushing up was consistently "on", and pushing down was "off", regardless of which switch was last used to control the light. The system used external latching relays which connected to the switches via low-voltage wiring; I would expect one could design modules to operate with standard "3-way" or "4-way" lamp wiring [one module would house the relay; the others would "pass through" one leg and switch the other with a diode. – supercat Jan 13 '14 at 16:34

It's mechanically simple, which makes it cheaper and more durable than alternatives.

And once that became the standard, the affordance was set, so the value of switching* to something else was outweighed by the confused that would be caused.

*pun intended

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Imagine you come home and go to turn on the light, but nothing happens when you flip the switch.

You try it back and forth a few times before identifying that it's blown.

It's no longer clear to you what state the switch was in when you came home, but you can still reduce your risk of electrocution by putting the switch back into the "off" position before changing the bulb.

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No one else seems to have mentioned that switch in the physical world is a lot easier to operate with it's current design.

A push button would require a hand push or finger push in one direction to operate, whereas a flick switch can be operated with a swipe from a certain direction (as well as, in the case of the pictured, modern switch a push on the right part). This increases the target area in 3d space in line with Fitts Law:

This increase in target area has further use in the physical world as we can operate the switch more easily with elbows, foreheads, even knees, or by pushing at it with something. Not to mention in the dark.

Another distinct advantage is that it's easier to push multiple switches at once, for example, a room that has three or four light sources and we want to swicth the lights of before bed, one swipe of the hand, or a straight finger in the right position and all switches are off. This becomes even more of an advantage in more complex situations where there might be 20 or 30 switches.

In a computer this sort of functionality needs to be pre programmed (select all checkboxes for example) whereas in a physical system the direct interaction can be done without extra system functionality.

The difference is simply that when using with a physical system we interact directly with systems physical form but when using a computer system we interact via purposely designed interface tools. This difference means that flick switches are good solutions to toggling in the real world and click buttons are good toggling solutions when a mouse pointer is involved.

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Building on your "20 or 30 switches" thing: You can ususall angle your hand and just slide it horizontally and hit them all up (at a risk of slightly hurting yourself from the switches rubbing on your palm behind you; but you get used to it after a while). – Cole Johnson Apr 4 '14 at 15:51

The word "toggle" originally meant (from an online dictionary) "a pin, bolt, or rod placed transversely through a chain, an eye or ... an ornamental, rod-shaped button for inserting into a large buttonhole, loop," so it has to do with shape, not to do with being a two-state device. We have altered the meaning of the word, and the question is about meanings. You have simply revealed that the change in use of a word has caused confusion. The meaning of words and statements should be so obvious as to be unarguable, otherwise we waste energy communicating instead of solving problems. "A tempest in a teapot."

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