... center according to the communication protocol directly over wireless GPRS network.The GSM GPRS Power Facility Alarm (GSM GPRS Outdoor Alarm Controller) S250 ... with input occurrence alarm;11.Supports two way voice communication;12.Supports external siren, the siren working time is ... ,EGSM900 Class4(2W)DCS1800,PCS1900 Class1(1W)GPRS Protocol: GSM,GPRS Phase2/2+GPRS Data: GPRS CLASS12, CS 1,CS 2,CS 3 ...