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Mad Dog said:Connecting to the PCM's 'mute' didn't take (probably needs the resistor that was suggested to step down the signal?);



It is likely that an open-collector, NPN transistor is the appropriate way to connect the mute output from the telephone, to the mute input on the PCM2. It will "pull down" the mute input.

An alternate is to use a relay. Select a low current +12V relay, energize the coil with the telephone output. Have the common contact connected to ground and the normally open contact to the mute input.