What is this switch for?

[Senegoid]

@Grestarian

That button turns all the intersection lights red so nobodyi’s in our way when we get rolling!

In Honolulu, last time I was there (about 40 years ago), the lights at major intersections turned red in all directions whenever a fire engine approached, beginning while the fire truck was still a few blocks away it seemed like. As far as I could tell, this was true all over the city, and not just near the fire station. Furthermore, there was a siren mounted somewhere near each such intersection, at the top of one of the light posts, that sounded too.

I never did learn how or where these were controlled. Was it controlled from some master control panel at the fire station? Or by radio from the fire truck? Or by some kind of automated transponder on the fire truck?

(Any Hawaiians here know?)

What similar devices exist in other major cities?

[GaryM]

@Grestarian

My friend pointed to the roll-up doors for the garage and said, “I glanced out and saw the traffic. That button turns all the intersection lights red so nobodyi’s in our way when we get rolling!”

If that’s available in a portable version, put me on the list.

[GaryM]

One known method uses a receiver that picks up the flash sequence of the emergency lights on the truck to then control the lights.

Nowadays they could be using GPS data.

Signal Preemption Wiki

[Ann_Hedonia]

@Mama_Zappa

Each of those lights has other switches: the main ceiling lights can be controlled by a switch by the 2 steps into the family room, as well as a switch going into the dining room. The table light can also be controlled by a switch near the table.

Every now and then, all the switches will be down - and one of the sets of lights will still be on. Baffling.

Not that baffling, that’s how the 3 way switches work — they aren’t up=on and down=off.

You walk into the room, both switches are down and the light is off. You flip the switch in location 1 up and the light goes on. You walk to location 2 and turn the light off by flipping the switch down. Walk back to location 1 and you turn the light on by flipping that switch ( which is still in the up position) down. Voila- your lights are on and both switches are down.

Sone of the newer switches are electronic tap switches with LED indicators. There is no up and down and the LED can correctly track the state of the light.
But for a 3 way ( 2 switches for one circuit of lights) or 4 way ( 3 switches for one circuit of lights) switching application using older, fully mechanical switches—— the state of the switch doesn’t track the state of the light.

It can be confusing, especially when you are dealing with switch banks that controlled 5, 6 or more circuits of lighting.

I used to do this professionally, BTW.

[Mama_Zappa]

@Ann_Hedonia

Not that baffling, that’s how the 3 way switches work — they aren’t up=on and down=off.

You walk into the room, both switches are down and the light is off. You flip the switch in location 1 up and the light goes on. You walk to location 2 and turn the light off by flipping the switch down. Walk back to location 1 and you turn the light on by flipping that switch ( which is still in the up position) down. Voila- your lights are on and both switches are down.

Well yeah - I understand that scenario. My bafflement is that there are three switches. Usually when all 3 are down, the light is off.

So if the three are abc (all down) vs ABC (all up):
abc = off
Abc = on
ABc = off
ABC = on
aBC = off
abC = on
abc = off

I haven’t figured out the sequence of flips where three switches all off would give different results different times. I’m sure I’ve missed a step somewhere, or have miscounted switches, or whatever. It’s a mildly entertaining conundrum.

Also I think you got the up/down in your example wrong: if both are down when you begin, then you go from
ab = off
Ab = on
AB = off
i.e. both are up, but the light is off.

If a circuit were wired in such a way that aB or Ab ever meant off, it would be a quick way to drive a resident bats :D.

[Mama_Zappa]

Here’s how emergency vehicles change traffic lights on the fly

[Senegoid]

@Mama_Zappa

So if the three are abc (all down) vs ABC (all up):
abc = off
Abc = on
ABc = off
ABC = on
aBC = off
abC = on
abc = off

I haven’t figured out the sequence of flips where three switches all off would give different results different times. I’m sure I’ve missed a step somewhere, or have miscounted switches, or whatever. It’s a mildly entertaining conundrum.

You missed:

• aBc = on
• AbC = off

The state of the light (on or off) is completely deterministic. Any configuration of the switches that has the light off will always have the light off. Any configuration of the switches that has the light on will always have the light on.

[Jasmine]

@FairyChatMom

But there’s another switch in the hall that doesn’t seem to do anything. There are no outlets in the hall, so that’s not it. Neither the coat closet nor the linen closet are lighted, so that’s not it either. If it controls an outlet somewhere, that should be simple enough to figure out - we just plug lamps into all the sockets and flip switches. beyond that, I have no idea how to figure it out, short of climbing into the attic.

Ha!!! I find this hysterical because of an old “Married with Children” episode that involved an unidentified light switch. It ended with Al flipping it on and off, on and off, wondering what in the world it connected to. Suddenly the scene switched to Buck’s doghouse in the backyard and ended with an apathetic Buck wondering who in the world was flipping his light on and off over and over again.

[FairyChatMom]

Aha - their house has a separate studio on the other side of the back deck. It never occurred to me to check if it does something out there. I’ll suggest it to them.

[GaryM]

I have a set of flood lights on the back/side of my house controlled from four positions. The only way to be sure the lights are off, or on in daylight, is to look at one of the fixtures.

[gotpasswords]

There is a mystery switch in my kitchen next to the door to the garage. Logically, it would be a 3-way switch for the kitchen lights, but it does nothing. One of these days I’ll have to pull it out to see if it’s even connected to anything.

At least it’s not like the 3-way switch in my partner’s kitchen. A couple weeks ago he said it smelled like frying fish in the kitchen. Then he discovered one of the light switches and surrounding wall was hot. I had him flip unlabeled circuit breakers until the light went out. I went over, and found “drunk uncle” wiring. They had a hot wire, a wire presumably to the switch at the other end of the room, and a neutral connected to it. If the screws were tight, there’d be a dead short. But, the screw was loose, making for a poor connection so it and the wire could get hot.

I have no idea how it ever worked without immediately tripping the breaker. Rather than try to figure out the mess, we’re probably going to use a wireless 3-way switch setup and ignore the wiring.