DB Systems audio amplifier is a remotely controlled electronic unit that operates on command from switches and potentiometers in the cockpit. Capable of switching an separately controlling the volume for up to 12 receiver inputs. Switches five sidetone inputs and interphone line. Two unmuted inputs and unswitches are provided to accommodate an aural warning input and an auxiliary input. Part 438-005 has custom configuration for a 7 station interphone system that uses model 907 Audio Switching Unit to control the interphone line connections between stations. Receiver levels are increased ot compensate for the receiver levels that are also increased to compensate for the increased load. The AUX input is used for interphone input and the INPH OUT is used for output.