An Alarm System was developed which used commercially available PIR sensors for indoor detection. A resistive loop is used to protect garden shed's and garage. Once set, the unit allows about 1 minute before arming itself, if at any point the unit is triggered an external siren will sound for around 15 minutes before the unit resets itself, the system is mains powered with full battery back up.

This design was published in Practical Electronics, September 1995.