The Remote Microphones are equipped with programmable function keys to perform zone selection, group selection and matrix functions. The units are connected to the main system via RS 485 up to 1.2 km. All models feature built-in chime, audio gain control and 20 kHz pilot signal for audio path diagnosis. An auto mic off feature monitors the microphone for inactivity and automatically shuts it off to prevent the unit from occupying the system.