This is a circuit of a simple but effective burglar alarm, which shows the status of each sensor with a separate LED. This allows you to see at a glance whether any doors or windows aren’t closed properly before switching the alarm on. This article describes a design of a burglar alarm that can monitor up to eight sensors. The status of each individual sensor is indicated with an LED. This LED shows whether the sensor has been activated and whether the wiring to the sensor is in order. Obviously, this burglar alarm also has an input to ‘arm’ the alarm, a tamper input and a couple of outputs to control a siren and/or a strobe light. The alarm is also fitted with a socalled ‘panic button’.