The RM-200SF is a Fireman's Microphone of the matrix system. It is equipped with an emergency key, permitting it to be used as a remote microphone for emergency broadcast. Zone selection and microphone announcement can be made at the time of emergency broadcast. It offers a surveillance function to detect failures including microphone element failure. The RM-200SF has three function keys that can be set as individual or group selection keys, and each key is linked with the corresponding two indicators. Connecting the optional RM-210, RM-320F Extension units to the RM-200SF expands the number of function keys and indicators in blocks of ten.