How Do I Fix My Burglar Alarm?
Sensors are electronic/electrical devices and in the context of security alarms, they either detect entry of an intruder into a building via a window or door, or directly detect the intruders presence. They are small modules which contain microswitches which are normally closed. The switch contacts are normally "volt free". This means that they are isolated from the electronics of the sensor, so that they can be connected to any external voltage source. When a sensor is activated, the microswitch opens and breaks a circuit. The alarm panel detects this and activates an external wall and internal sounder. The panel may autodial a phone number or send an SMS text message to a ce