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Suppose a blind person wanted to know whether a switch (such as a light switch) was on or off (also suppose the switch was vertical.

Wouldn't it be natural to think that top (=1), would mean on, and bottom (=0), would mean off.

You think about the scenarios (I might edit the question, later).

But then what if more than one switch was connected to the same light? For the case of two switches

U: SameOrientation = {((0,1), (0,1)), ((1,0), (1,0))}

V: DifferentOrientation = {((0,1), (1,0)), ((1,0), (0,1))}

for which there are only two possible electrical wiring configurations:

U = Off, V = On

or

U = On, V = Off

In both cases, for the switches to "be standard", both switches would need to communicate, via a circuit, so that when one would be propped on, the other one would switch on as well (just the same if one is switched off: and the other switch automatically switches off as well).

Any other ideas, or views?

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    I've had the big rocker toggles, flip toggles, and old-style push-buttons in my homes. In every case top meant on except when there was a 3-way switch present. That screws everything up. – plainclothes Dec 10 '15 at 23:52
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    @plainclothes, just to confuse things, in Britain, down = on. – user31143 Dec 11 '15 at 6:04
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    @JackMaddington Moving switches in sympathy requires actuator motors and all sorts. It's a lot more expensive than a simple switch. And now there are available wireless switch-plates which rest in a "neutral" position and are pushed either top or bottom to activate the actual electrical circuit breaker concealed in the ceiling. You can have many more than one of the switch-plates control the on-off action. The neutral position conveys no information at all, but it is always the same action to turn the light on or off via any of the switch-plates. – Andrew Leach Dec 11 '15 at 9:14
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    There are light switches that indicate their state via a little light on the switch. A blind person cannot see that, but then, they might not be the primary target audience for a light switch, anyway. Still, the issue remains that any tactile output will invariably require some controlled moving parts. – O. R. Mapper Dec 11 '15 at 10:10
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    Image at mkelectric.com/en-gb/Products/WD/Echo/Pages/default.aspx Benefits: put them anywhere without running wires through the wall. Relevance: there is not even any positional data about the state of the switch. – Andrew Leach Dec 11 '15 at 11:07
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If you really need to inform visually impaired people about light switches state you can not rely in position (as it has already been said).

For one-way switches you can help them with braille light switches:

switch with braille

They're uncommon (then more expansive) but they exists and you can always stick a braille text on existing ones:

Normal light switch with braille text

Multi-way switches are harder to handle but they do not need to communicate with each other: in a two-way switch, each switch knows if it has a load or not (think about switches with light):

two points

Your challenge is to use this information to change switch state. Some switches have this kind of connection (usually to light a small lamp) and with little logic you can use it to update a single character braille display. Again it's (relatively) expansive but you do not need extra cables between your switches then all extra cabling is made around each light switch point. You may use Electric Active Plastic for this purpose:

EAP example

When you have to deal with n-way switches: n points

Things may be little bit more complicate (especially if you rely on high availability products) but in addition to what said above you may also:

  • Do not connect switches directly to main electric line. They use lower voltage to command a relay. You need more cabling (because of relay's feedback) but they're small low voltage inexpensive cables. After this same solution of above applies.
  • Use a product specific for home automation. There are braille touch displays and they can be used by any kind of user.

Note that this has already been done with credit cards then technology exists and it's accessible:

Braille cc

One final note: all above solution for multi-way switches are somehow expansive. I'm sure there is a niche market but if DIY isn't an option you may spend a lot. However...don't forget that visually impaired people still have other senses! For example a simple push button (with braille on its ring for identification) may trigger audio feedback by proximity. This is pretty cheap (a quick search gave prices ~30/40$ per peace) and it works well.

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  • I'm reading throughy your post, which is remarkable. Could youexplain how braille light switches work, perhaps by posting a video. Also, what do you mean by espansive: are these widespread, or do you mean somehow these expand in some way. ? – Jack Maddington Dec 11 '15 at 17:37
  • In your second diagram, what is this "3-way" text? All I see is two switches connected serially. Also, why is the bottom (disconnected) part of the circuit black, (and not red)? – Jack Maddington Dec 11 '15 at 17:45
  • Starting from second question: someone (including me) prefers to call "switches" (on/off) two-way switches (official name). Let me simplify: they alternatively connect two pins (from three). AB or AC current has two ways and when one pin is floating they're simply acting on/off. What officially are 3-ways (because they have 3 pins) do not have disconnected pins then current can flow in two-ways. There is not a disconnected part in that circuit, it hot (red) and neutral (black) connection. – Adriano Repetti Dec 11 '15 at 18:13
  • A braille switch is simply a switch with braille text. It can be to identify the switch or to determine which state is on and which off. For an example see (like in that picture, see products.z-wavealliance.org/products/599). Advanced switches (like that one) can be used in home automation in conjunction with braille displays (see also ux.stackexchange.com/a/86780/13161) or with DIY solutions (using EAP or other home-made solutions). – Adriano Repetti Dec 11 '15 at 18:17
  • With "expensive" I mean they cost more money that normal switches (even much more if you need braille displays and/or home automation stuff). That's why my last paragraph suggest also something else (audio feedback when finger is near the button, labeled with braille for identification). – Adriano Repetti Dec 11 '15 at 18:18
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There is no international standard for lightswitches. In some countries (e.g. America), up always means on. In others (e.g. Great Britain) down means on.

And in any country, having multiple switches connected to the same light means that you can't tell the state of the light from the state of a given switch.

Update: there is a lot more detail in this answer from the question mentioned above.

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