Monitors audio activity over a wide range of input voltages Two sets of C-form (both N.O and N.C) relay contacts respond to audio activity Four levels of signals: microphone, 600-ohm line, 25V, and 70V speaker systems Built-in balanced, low noise, high gain microphone pre-am Transformer-isolated, 600-ohm small signal level output of detected audio available Works with self-amplified or central-amplified paging systems Separate microphone pre-amp gain control Adjustable release delay: 0.25s to 25s Trigger threshold adjustment Relay active indicator light Accessories: PRS40C 12V DC Power Supply (Sold separately)