Making a home telephone ring with battery?

[E]

Is it possible to activate a standard home telephone ringer with an off the shelf battery/wires/switch?

[The Natural Philosopher]

Depends which shelf. Needs about 50VAC IIRC.

[Andy Dingley]

_Intended_ to use 75V AC. Actually _needs_ about 20V AC (personal experience, but this will vary considerably).

It won't ring with a DC voltage, as the bells needs AC to ring - with DC they'll just go "ting". Even if an electronic squawker might respond to DC, as a "ringer" it's wired into a circuit with a series capacitor. Phones naturally have 50V DC on the line, so a ringer needs to be insensitive to this!

The old GPO way of arranging local ringing was a relay and mains transformer to switch AC. You can find these sets on eBay. Another way would be a hand-cranked generator 26, again easy enough to find on eBay (tenner-ish, but watch postage as they're heavy).

[Dave Plowman (News)]

No. They work on AC. And not even the same frequency as mains.

[Peter Andrews]

To be precise: a ringing signal of 40 to 100 volts (typically 70v) rms at

25 ±1 Hz

Peter

[Dave Plowman (News)]

Maplin used to do a ringer kit. Not Vellerman - one of their own. Worked well - used it for theatre stuff. I've still got the circuit if anyone wants it. Did UK and US ring intervals. Used a mains to 6 volt transformer the wrong way round to get the volts from the oscillator.

[Frank Erskine]

I also built of of them - for a theatre too!

I modified it a bit to give a ring on cue rather than having to wait up to 2 seconds for the (UK) ring cycle to come round. I arranged a monostable to reset the counter when the 'ring' switch was operated.

Allegedly it didn't work with a traditional 1000 ohm bell, but it did ring it OK. It was better however with the newer 4000 ohm ones (and of course modern 'sounders').

[Frank Erskine]

Some early ringing machines operated at 16 2/3 Hz (1/3 of mains frequency).

[Dave Plowman (News)]

I changed the output transistors to handle more current.

[NT]

Yes. How depends whether youre using an old mechanical bell phone or a modern electronic one, or need to cover both.

All phones respond well to 70v ac 16-25Hz.

Modern ones will respond fine to the output of a mains transformer at

20v, and sometimes a lot less.

Mechanical bell ringers are more demanding, but you can mess with their 70v 16-25Hz supply a fair bit and still have them ring.

You can also fire phone ringers using a battery and a self oscillating relay to produce voltage spikes.

NT

[terry]

Re; All phones respond to ......... 16 - 25 hertz.

That's generally true. But there were/are ringing systems around the world where several different frequencies were used on multiparty lines. It was system designed so that the phone bells of 'other' parties on the same line would not ring! So party A, for example might be 25 hertz, B 33.3 hertz, C 50 hertz and D 66.6 hertz etc. In one system there were actually five different ringing frequencies. And by arranging five phone ringers from each side of the line to ground it was possible to have up to ten parties, with secretive ringing, on one line! Mainly used on long rural lines. Unlike manual ringing, where all the phones on the line would ring to coded signals e.g. two shorts and along would be farmer Smith etc. special arrangements then had to be made on secret ringing lines to allow one party on the line to call another! Not likely any of those secret ringing or so-called 'Harmonic Ringing' phones around now

[NT]

Never knew that. Did the bells discriminate by mechanical resonance?

66Hz seems a very high frequency to operate a mechanical arm at

NT