ABSTRACT
Monitored systems incorporate remote supervision through the telecommunications cables linked into the alarm circuit to a security company and possibly the local police. Intruder alarms have developed from a very limited specialist element of electrical installation work in high-security buildings to the much wider market of schools, shops, offices, housing. An alternative is a wire-free or radio frequency installation that has appeal to the DIY market. Hammering or structural impact produces vibration in the pendulum, sufficient for the contacts to meet and complete a detector circuit. Magnetic reed –can be used in the same situations as a micro-switch but it has the advantage of no moving parts. It is also less exposed to damage or tampering. An intruder penetrating the microwaves disturbs the frequency which effects the detector circuit. Infra-red beams will penetrate glass partitions and windows, each pane of glass reducing the beam effectiveness by about 16%.
