A small cordles emit board set inside the lock,you can't see from outside, when home people open the door with key,it will not triggers the motion sensor,and can't emit a signal to base, the thieve can't open the door with key, for the key is special,it is curve chain ,the thieve may spoil the door,at this time, it triggers the motion sensor ,and emit cordless signal to the base which is connected to a
phone line,the base will automatically dial the preprogrammed numbers of a telephone, moblie phone or pager for audio monitoring
This is the best unit for protecting your home, office, wherehouse or store. It is easy to install or relocate. Just plug and play.