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.