A microphone unit comprising a voice input for receiving a voice input signal, an analog to digital converter for creating a digital signal from voice signal, a voice coding device for creating a voice coded signal output from the digital signal, encryption means for encrypting the voice coded signal, and a modulator for generating a transmittable signal that can be supplied to a radio via the microphone input. Additionally, the microphone unit is capable of performing the steps in reverse upon receiving an encrypted signal. The received signal output from the radio is demodulated, un-encrypted, voice decoded, converted from a digital voice signal to an analog voice signal, and output via a speaker which is preferably built into the microphone unit.