Classic car Thatcham category 1 alarm and immobiliser

There are two types of intruder sensor, ultrasonic or microwave. For a classic car a microwave sensor can easily be fitted under the carpet rather than two ultrasonic sensors fitted at the top of the two front door pillars which can look ugly if the cable can't be hidden behind any trim.

Open top cars MUST be fitted with a microwave sensors and some cars pre dating the 70s may have positive earth or a 6 volt supply rather than the usual 12 volt negative earth power supply.