Siren is designed for alarming people when fire hazard is detected to let them evacuate. LVP-D is a loop voice siren which is powered by external power supply. After activation acoustic sound starts and then voice announcment. Depends on configuration these devices can activate 3 diffrent comunicates. It can work on addressable loop circuits/stub circuits of AWEX FAS system only. Connection of power wires are mandatory. LVP-D siren have built-in detector base whichlets use this device as sounder and detector at once.