On Nov 22, 6:13*am, terry wrote:
On Nov 21, 9:57*pm, NT wrote:



On Nov 21, 9:26*pm, E wrote:

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

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

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

Never knew that. Did the bells discriminate by mechanical resonance?
66Hz seems a very high frequency to operate a mechanical arm at


NT