Now the security alarm system is realised, as a rule, on the basis of infra-red (Ir) - the detectors providing fixing of the malefactor on thermal (Ir) to radiation. Modern Ir-detectors possess in the small sizes and aesthetic design.

The security alarm system on base Ir - detectors is necessarily equipped with the reserve accumulators providing power supplies at failures of the electric power. Powerful dynamic or siren will provide strong psychological influence on the malefactor.

If you build a country house we can equip with its system of the security (security-fire) alarm system. Thus it is important to have time to put conducting of chains of the alarm system (as well as chains electricians, a telephony) prior to the beginning of shtukaturno-painting and decorating. Chains of the security alarm system are spent by a special wire, with the automatic control of integrity and absence of short circuits.

If house furnish (or apartments) is already finished, installation of the wireless (radio channel) alarm system is possible. Wireless alarm systems are characterised by smaller noise immunity, but they are more mobile and are convenient for embedding in an existing interior.

Modern systems of safety of objects, all of them possess common fault: cannot provide early detecting of intrusion on object territory. All modern systems of protection, as a rule, are focused on detection of the infringer which has already got on protected territory or into a building. The qualified infringer always counts on a certain time window which passes from the penetration moment on object till the moment of operation of the alarm system. Minimisation of this interval of time is the radical factor defining efficiency of any security system, and in this sense appeal on perimetre the security alarm system is conclusive.

The perimetralnaja border of object is the best place for early detecting of intrusion since the infringer co-operates first of all with physical perimetre and creates indignations which can be registered special gauges. If the perimetre represents a protection in the form of a metal lattice it should be cut or overcome from above; if it is a wall or a barrier through them it is necessary to get (or to do undermining); if it is a wall or a building roof they need to be destroyed; if it is open territory it needs to be crossed.

The gauge any on perimetre systems reacts to crossing by the infringer of a line of protection. Gauge signals are analyzed by the electronic block (the analyzer or the processor) which, in turn, generates an alarm signal at excess of the set threshold level of activity in a protected zone.

Advantages of protection on perimetre:

• Possibility of early detection of the infringer even before its penetration into protected buildings, premises;
• Exact following to perimetre contours, absence of "dead" zones;
  Whenever possible latent installation of gauges of system;
• Independence of parametres of system of a season (winter, summer) and weather conditions (a rain, a wind, hailstones etc.);
• Immunity to external factors of "not disturbing" character industrial radio noises, noise of transport passing nearby, small animals and birds;
• Stability to electromagnetic hindrances lightning discharges, sources of powerful electromagnetic radiations, etc.