Weirdest reason to leave for job on time (or less late anyway): gigantic power outage in my part of town. :P
@barefootstache I only forgot to turn off one light when I left for work. But that's alright, heh. Hard to check whether your lights are still on or off during a power outage. :D
@trinsec unless you know how the position of the switches should be
@barefootstache Of this particular one it's impossible. It's a 'hotelschakeling'. Means there are 2 switches for one light. Those switches could be in either position.
@trinsec well yes, though only a certain amount of permutation will make the light be on or off
@barefootstache Not sure I understand you. Two switches for one lamp means either one can be in either or both or whatever position for being on or being off. It cannot be predicted. One switch is upstairs, other's downstairs (for the stairwell).
@trinsec If we have two lights A and B, and they both only have two states 1 and 0, then there are a total of four permutations:
00
01
10
11
From these four permutation only two of them will make the light be off and the other two make it be on. (unless the electrician did some mean non-standard design)
Typically one would group the permutation like this:
00, 11 (j)
01, 10 (k)
Thus one would only have to know what state the light would have if (j) is true.
@trinsec lights A and B are meant to be switches A and B
@barefootstache @trinsec Wait a minute. When you guys have multiple switches for 1 light, it should be the case that so long as exactly 1 switch is on, the light is on, right? That's how it's always been at the various places I've lived. i.e. A xor B -> light
@barefootstache @trinsec flip one of your switches and you can make it XOR ;)
@johnabs @barefootstache Somehow me trying to upload a GIF animation doesn't seem to animate well.. fine, here's a direct link:
https://media.natuurkunde.nl/content_files/files/9463/original/wisselschakeling.gif
@trinsec @barefootstache what if they're both toggled to the top wire? Does the bulb turn on?
@trinsec @barefootstache so...its just if they're in the same position as each other, right?
@johnabs @barefootstache Apparently so. Never really thought about it. Since they're both upstairs and downstairs paired with other switches (normal switches). And to go upstairs or downstairs to check is annoying. :D
@trinsec @barefootstache Fair enough! I was just thinking "is this some European electrical engineering thing I'm too American to understand"? 
@johnabs @barefootstache Heh, naw, doubt it. I'm sure this idea's universal for a 2-switch system.
@trinsec had that experience once also