[SML] Telephone line simulator

[Dan Sheehan]

thanks Jerry

* doorbell transformer would probably work,
or any small thing (wall wart?) with a very roughly 1:10 ratio (ie made for
120V to ~12V AC),
 provided the 20Hz source (amp) can drive the low end of it

On Sat, Apr 11, 2020 at 1:58 AM Jerry Durand via Stagecraft <
stagecraft at theatrical.net> wrote:

> For the low of budget people, if you just need to generate ring you can do
> so with bits you might have laying around.
>
> You'll need:
> An audio source for 20Hz sine wave, pulsed in whatever cadence you want.
>
> An audio amplifier, I used a Radio Shack PA amplifier for one setup.
> Doesn't need to be quality, just function.
>
> If the amplifier has 70 volt line out, you can skip the transformer in the
> next line.
>
> * >An 8 ohm to 70 volt PA transformer. <*
>
> A blocking capacitor, steal a RUN capacitor from an induction motor you're
> not using.
>
> The capacitor isn't strictly needed, but does limit current.
>
> Circuit is audio source > amplifier > 8-transformer-70 > capacitor in
> series with one lead > telephone.
>
> Be sure and cut the audio when the actor picks up, you don't want to blast
> his ear with the ring signal.  Maybe remove the speaker from the phone.
>
> Experiment to find what works well with your phone and gear.
>
>
>
> ---
> Jerry Durand, Durand Interstellar, Inc. +1 408 356-3886
> <http://www.DurandInterstellar.com>www.DurandInterstellar.com &
> <http://www.DurandInterstellar.ru>www.DurandInterstellar.ru
>
>>
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-- 
...Dan Sheehan
Fixer of things that break
TD Walpole (MA) Footlighters
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