"Derek,

This unit keeps the relay on whilst there is sound being picked up by the integral microphone. When the sound stops, the relay opens. I woudl anticpate there being a delay between going quiet and the relay opening otherwise a tape recorder as a suggested application would be 'hunting'. What I do not know is how long the time period is and there does not appear to be an adjustment for this delay but would expect it to be a few seconds. However, it is quite likely that a simple component change could adjust this time period. As a last resort, an additional monostable timer on the output could achieve the same. "

– Admin