While not limited thereto, the present invention is particularly adapted for use as a telephone communication system for underground mines and the like. In such communication systems, there must be capability for private conversations between any two stations in the system. In addition, general paging must be provided whereby a voice message from one station is broadcast from a loud-speaker at every other station in the system. It is also desirable to provide for data transfer derived, for example, from monitoring devices which produce signals indicating an off-normal condition such as a fire at a particular location within the mine. Telephone systems of this type are battery-operated; and provision must be made to conserve battery power by connecting the battery to the circuitry at a station in the system only when it is transmitting or receiving a signal.