The ST-VOX1 is an Audio Controlled Relay in the STICK-ON series. When used in intercom or talkback applications, the ST-VOX1 may be triggered directly from an unbalanced microphone. In many such installations the microphone or other audio source must be preamplified, making the ST-VOX1 an ideal mate to work with the STM-1 preamp. The unbalanced output from the STM-1 can be used to trigger the ST-VOX1, while the STM-1 balanced output is used for the audio feed.