Pre-amplifier for microphone- and line-signals and an envelope follower. If the signal exceeds a certain (adjustable) threshold a comparator outputs a gate signal which you can e.g. use to fire an envelope. But you can use the module also as a small active multiple.
The A-119 has two different audio inputs: an unbalanced with 1/8" socket and a amplification 0-20 for line levels as well as a balanced one with 1/4" socket, amplification factor 0-500, primarily intended for microphones and guitars or other instruments.
The Envelope Follower reads the signal level of the input, and puts out a proportional voltage as an envelope at it's 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.