Strange old smoke detectors - anyone know what they are?

That looks kind of industrial. I tried looking up the address, but found a laundry, The 'House of Dobey'.

That's at no. 72.

This is the address and a likely contender

I'm guessing the OP's house at some time was a B&B

Owain

That's nos.70-72 Avon Instrumentation Services Ltd was nos.76-78, although A.P.E Fire & Security Ltd is there now which may not be the same people.

It's what it says, an ionisation smoke detector. What did you really want to know?

NT

Fairly common smoke detector without a built in alarm designed to be wired to a central fire detection/alarm panel. (Similar to an intruder alarm panel). More usually found in industrial/commercial premises.

That address sounds familiar. I used to have a smoke detector with that address next to a radiation symbol on a large metal piece inside a plastic case. In the end I gave it to the bloke at the local tip who put it on a pile of others. I would have thought if it was as old as mine the radioactivity would have gone by now since that presumably was why it no longer detected anything!

Brian

I was just curious as I'd not come actoss a smoke detector like this one, and I wondered if anyone knew what it was.

Every domestic smoke detector I've seen over the past twenty years or so has either been 9v battery or battery + mains. I've never seen one powered by 12v before. It also doesn't have any press-to-test switch, and doesn't appear to have a speaker, so presumably the alarm function would be from a central alarm box or something.

Thanks. That makes sense. I suspect the central panel was removed at some point, which is why there's no 12v supply. This reinforces my view that they need to be replaced with something more modern.

I think they get clogged or something. Maybe that's why manufacturers favour the kind where you have to replace the whole thing. (More likely they make more money that way as they don't sell PP3s.)

On looking again, I think that one was intended to be used with an intruder alarm panel.

Fire systems use 24 volts, not 12 volts, and wouldn't have C/NC/No contacts.

Smaller panels, up to about 4 zones. commonly used (and still do)

Again, on older small alarm systems relay switching was the norm together with a couple of diodes to allow the head to be removed for cleaning without the alarm going off. (Usually just a twist lock).

You made your post just before I set off to do a bit of travelling for work.

The first job I went to had what looked like the same alarm.

I'll be going back there at the weekend.

It's almost certainly connected to the intruder alarm.