... keypad; Big LCD displays2. GSM+PSTN dual net Li-Ion backup battery 3.7V 800mAH home security system with Lcd touch screen Feature ... Contact ID protocol(alarm information, status information, AC power off and recover, Low voltage, test)8. Support wireless “ding-dong” doorbell ... Main alarm set, 2 wireless remote control,1 pir sensor,1 door sensor, 1 adaptor,1 backup battery, 1 siren. 1 English ...