🚀 go-pugleaf

In article <Bz6nyz.LF4@acsu.buffalo.edu> v064mb9k@ubvmsd.cc.buffalo.edu (NEIL GANDLER) writes:
>
> I am designing a device that disconnects a pair of speakers from a
>stereo recevier when the phone rings. But when the phone is eventually
>hung up m afraid that suddenly switching back a pair of speakers with a
>relay during high volumes can sort of "overwhelm" a pair of
>sepakers

	If you just want to mute the receiver, DON'T use a relay
in the (high-current) speaker wiring.  Instead, put a two-resistor
attenuator in your tape monitor loop, with the grounded resistor
being a photoresistor (most convenient way to do this is with
a lamp/photoresistor style optical isolator).

	When you light the light, the photoresistor turns ON
and mutes the stereo; when you remove the light, the photoresistor
slowly (takes a few milliseconds) turns off (and you can make
it slower by powering the light through an RC circuit).
Noise is negligible, because no current passes in the
photoresistor while the stereo is ON.

	If you have the schematics for the preamplifier, it would
be easy to build this gizmo into the box (it only takes a few cc
of volume).  And, it DOESN'T induce sharp switching transients.

	John Whitmore