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My DIY
doorphone project seems to be nearing the top of pile
again!
Can
someone point me to/design a circuit that does the
following?
A
small microphone listens out for a loud noise. On hearing said noise, it
opens a
relay and starts a 3 min. (maybe adjustable) countdown.
When
the countdown times out, the relay is closed and the system listens for the
noise again.
This
circuit when, combined with a gutted speakerphone, in a waterproof box,
plugged
into my PABX should function as a doorphone.
The
visitor rings the doorbell. I pick up the nearest phone and dial 27. The
PABX
routes it to (wants left of) the speakerphone.
The
'piggybacked' circuit hears the speakerphone ring and closes the relay,
this 'lifts the receiver's and I can talk to the
visitor.
When
I'm done I hang up. Sometime later the circuit hangs up the
speakerphone.
Nice
:)
If the
speakerphone could be powered by the phone line (hey isn't the speakerphone
too?) that would save another wall wart. It should be OK because it's
on
the internal line??
Thoughts/suggestions/ridicule appreciated.
Lee.
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