Re: TI-H: ot

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Re: TI-H: ot


Brenden McNeil wrote:
> 
> OK... I know this is off topic... but does anybody have a schematic for a
> telephone based intercom... I'd like the other phone to ring when the
> handset on one is picked up.
> 
> Any ideas?

well, you need a -48 vdc supply first off to power the phones.  you some
kind of circuit to detect when one goes off hook, the voltage across the
phone will drop to 6 to 10 volts.  then you need a ringer device the
must be 100 to 120 volts at 20 hz to ring the phone.  i have a little
device that generates the ring voltage when you apply +5 vdc to it.  i
know the guy that sells these devices at hamfests and he has 50 or more
of them for like $2 each.

let me look through my files here b/c i am sure i have some schematics
that will do what you need.  i built a full duplex laser phone link and
had to implement most of what you need to do.

Bryan Fields
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