All the information you need to build a vehicle anti-hijack alarm - using cheap off-the-shelf components.
Detailed Circuit Description
This material is being extensively re-written.
For the present - please Download the previous version of the page.
Before fitting this or any other engine cut-out to your vehicle - carefully consider both the safety implications of its possible failure - and the legal consequences of installing a device that could cause an accident. If you decide to proceed - you will need to use the highest standards of materials and workmanship.
The Flow Chart is another of Eric's suggestions. It will help you to visualize how the alarm is operated. It also explains the sequence of events that lead to siren activation - and subsequent engine failure.
Hijack Alarm No.1 - Construction Details