I'm wondering if anybody has plans for a privacy adapter so that if
multiple phones are
connected in parallel, only one can be used at a time, but all will
ring.
I know of commercial designs and components to do them, but I can't seem
to source
the component (HS-20 made by Teccor, currently discontiunued from what I
understand) and the design should work bidirectionally (non-polar
design).
If anybody out there knows of a simple and cheap design, or knows where
I can obtain
the part, please e-mail me.
Thanks.
Donny Mah <wf...@freenet.victoria.bc.ca> wrote in article
<3554F845...@freenet.victoria.bc.ca>...
One can be obtained from Dataparts Ltd, New Zealand.I use one, so other
members of the Household, don't cut me off the internet. :-), when they
pick up another phone.
You are looking at about $10 US for one.
Cheers Paul.
Donny Mah (wf...@freenet.victoria.bc.ca) wrote:
: Hi,
: I'm wondering if anybody has plans for a privacy adapter so that if
: multiple phones are
: connected in parallel, only one can be used at a time, but all will
: ring.
--
K7IQ
What this does is require that the telco line voltage exceed the 5-9
volt offhook voltage *plus* the zener voltage for the phone to work.
Once another phone is off hook the line voltage drops below 10 volts
and now the protected phones cannot join the call.
Zener diode cost is $.20 or so.
-Jim
> > Thanks.
> There are several designs possible. The cheapest one is to use two zener
> diodes (12V to 16V would be fine). Connect the zeners back to back in
> series with either tip or ring (insert the diodes in series with one
> side of the phone line, either anode to anode or cathode to cathode).
> What this does is require that the telco line voltage exceed the 5-9
> volt offhook voltage *plus* the zener voltage for the phone to work.
> Once another phone is off hook the line voltage drops below 10 volts
> and now the protected phones cannot join the call.
> Zener diode cost is $.20 or so.
> -Jim
A zener may work just fine for a single instrument like a fax or
answering machine and nothing else. But he wanted it for multiple
phones on the same line.
This won't work if all the phones on the line have zener diodes. The
first phone to pick up will leave phone plus zener voltage across the
line, which just means that the next phone that's picked up will have,
you guessed it, phone plus zener voltage, and it will conduct also.
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Donny Mah wrote in message <3554F845...@freenet.victoria.bc.ca>...