David Clark M-7A 150 ohms Civilian Impedance Boom Microphone, new condition, not for use with wire frame booms. The Model M-7A is an Electret, noise-cancelling microphone designed to operate in place of carbon and amplified dynamic microphones. Provides clear, crisp voice transmission. It will not operate in circuits that do not supply a DC bias voltage. Most modern aviation communications equipment do supply this required voltage. If unsure, consult with your radio technical manual or with your local avionics shop.
