This surface mounting Door Contact is very handy, not only can you fix them to traditional wooden and UPVC doors, you can also use them to protect windows and even garage doors!, They are constructed of plastic and have an operating gap of 20mm. Silver screw terminals indicate alarm circuit, Brass screws are used for terminating a tamper circuit or spare cables. Designed to be added Intruder Alarms, CCTV, Air Conditioning Units or any system that requires a NORMALLY OPEN contact (going closed circuit when the contact is seperated) Main Features: Plastic construction NORMALLY OPEN going CLOSED in alarm (when contact is seperated) Silver terminals denote alarm circuit Brass terminals for termination / tamper * If you are unsure is this will work in your on your exist.
eBay