Module A-119 (External Input / Envelope Follower) is designed to allow external audio signals to be integrated into the System A-100. It comprises a pre-amp, envelope follower, and comparator.
The pre-amp has two inputs: an unbalanced input for line level signals, with a gain factor of from 0 to 20, and a balanced input with a gain factor of from 0 to 500, for insertion of low level signals, for instance from a microphone or electric guitar.
The Envelope Follower reads the signal level of the input, and puts out a proportional voltage as an envelope at its own output.
The comparator generates a gate signal whenever the input goes above an adjustable trigger threshold.
Three LEDs help you keep track of overload, the envelope, and the gate signal.

For more detailed information please look at the English user's manual A119_man.pdf.