Mute Circuit

[defaced]

Randall Smith's patent for the circuit. Not sure if it will be of any help, but I remember looking this up a while ago:  http://www.google.com/patents/about/6621907_Mute_circuit_for_use_with_switch.html?id=e9sOAAAAEBAJ

[xenrelic]

If you have one turn on while the other turns off, it won't pulse and the J175 will stay open leaving a 100ohm connection to ground at the mute point, so you need to have both turn on, one with a slight delay so it pulses. I noticed this when I had both relays turn on simultaneously and the J175 didn't open at all, but when one relays turns on and the other turns off, the J175 remains open so having both relays turn on (one with a slight delay), you get the mute pulse.