The David Clark Company Model DC-87 Dynamic Moving Coil, noise-cancelling microphone that delivers clear, crisp voice transmission. The Model DC-87 is designed for use in military low impedance applications. It is a direct replacement for the M-87/AIC microphone. Place microphone no more than 1/8" from lips for optimum signal to noise ratio (maximum noise cancellation). The DC-87 microphone cannot operate in circuits that supply a DC bias voltage.