Model #VAR1 Voice Activated Relay Bogen VAR1 Tone Generator (req. 12V - 48V DC Power Supply, 100mA) The VAR1 Tone Generator is a relay device that monitors audio activity over a wide range of input voltages and operates two sets of C-Form relay contacts in response to detected activity. The VAR1 can be used to detect voltages as low as signals directly from a microphone or as high as signals from 70V speaker systems. A low level output of the detected audio, transformer-isolated from the input, is also made available for use with other equipment. Can be used as a balanced low-impedance mic pre-amp, also. Read More   $113.94