The Model 247 is a multipurpose audio mixing amplifier for mixing aural warning, cockpit voice recorder, or any other aircraft audio signals. Each input is adjustable to accept 0.25 VRMS microphone input signals, headphone audio signals from standard audio systems, or receiver audio signal up to 50 mW. The outputs are designed to drive any impedance from 8 to 10K. Additional inputs can be added by connecting one of the outputs to feed an input of another mixer.