EACH SYSTEM SHOULD BE "MADE TO MEASURE" for the rooms it needs to protect: it will be necessary to consider the kind of risks and the requirements of the customer to have an adequate system.

The outdoor protection is very useful as an anti-aggression pre-alarm when persons are inside, but the same must never directly trigger the sirens, as there is an elevated risk of improper outdoor alarms.

The perimetric protection is signalling breaking attempts of the accesses, whereas the volumetrical protection signals the intruder at the inside of the rooms; both together they form a double barrier which may directly activate all means of alarm, i.e. sirens and automatic phone diallers for calls for help.

The protections must be efficient locally for dissuasion, one of the basic goals of an alarm system, and inform at a distance at the same time. For this reason it is necessary to distribute the detectors and the means of alarm of the system in a balanced way, in the proportion of at least 1 outdoor siren + 1 indoor siren each 4 detectors which are installed, since investing all in detecting devices and control will not send away a possible intruder, being ineffective to create a situation of real panic, which principally can be obtained with sirens at the inside of the rooms.