HDX3100 Bus-system Fire Alarm Telephone System is composed of HDX3100 fire alarm telephone main set, HGT310B bus-system table & wall telephone extension, HGT320B telephone plug-hole socket, HGT340B telephone control module and HGT220A plug-hole telephone extension. The person on the spot can communicate with central control room by using this system when emergent event happens. This system also can be used for dispatching and directing spot staff on emergent messages which was get from other systems.