Functions: Widely used in hospital, lift , hotel, meeting room, hall, supermarket, travel place point, ect to deal with emergent calls from clients in time. This system contains 1 message receiving host, and 1-99 pcs emergent buttons according to your need. When user press the button , the emergent call message is send to message receiving host and the host can locate where the call come from then arrange help without delay . 　 Distance between the host and emergent buttons can be 500m, 1000m, 2000m, 3000m according to your need . Work wirelessly, easy to install . Features: 1.Work voltage: DV12V 2.Work current:：≤200mA 3.The message receiving host can record 10 seconds of voice 4.The message receiving host can discriminate and show the 99 emergent calls and store the latest 10 calls , the 10 calls history can be reviewed and deleted. 5.Rechargable battery can be put inside the message receiving host so that it can work even in the situation of power cut . 6.Frequency : 315MHZ