Home Alarm System 1,Touch keypad,Big LCD display 2,GSM+PSTN ... , AC power off and recover, Low voltage, test) 8. Support wireless “ding-dong” doorbell function 9. Alarm priority, Reset, ... 1User manual*1 FAQ of GSM Security System:1: About GSM frequency: it can support 850/900/1800/1900Mhz,all of ... world can be used!2: About warranty: we support 2 years warranty3: About delivery time: Normal time is ...