... Voice prompt function 1, PSTN & GSM, Voice prompt function ,the use of industrial GSM / GPRS communication module 850/900/1800/1900MHZ options ... each zone, peripheral zone sound alarm, silent alarm around the zone, internal zone audio alarm, silent alarm within the zone, 24-hour ... , and so on, wired telephone networks can not reach. GSM security alarm system with LED display and keyboard,, security ...