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MP500/4N-8-16 Installation
2.3
THE DEVICES USED TO CREATE AN ALARM SYSTEM
Essentially, an intrusion alarm system consists of four types of components:
the control panel;
the detectors;
the signalling devices;
the complementary devices.
These components are generally separate, but sometimes a single device may enclose more than one.
Below are illustrations of these components: what they are called, how they are made, and how they work.
2.3.1 The control panel
The control panel is the "brain" of the system and has various functions:
it interprets different signals that arrive from the detectors and then takes the most appropriate action, like ignoring the opening of
a window if the system is disarmed or activating notification devices if it is opened while the system is armed;
check that all the system devices are always functioning correctly;
signal potential anomalies that may threaten security and the functionality of the system;
record all the main events.
An intrusion alarm system only has one control panel.
2.3.2 The detectors
The detectors are devices capable of detecting changes - voluntary or involuntary - that an element or physical characteristic of the
environment where they are installed may undergo. A detector has one or more sensors that perceive these changes.
The detectors must be designed and installed so as to maximise the detection and minimise the risk of false alarms.
For the alarm system, the detectors are equivalent to our senses.
The detectors may distinguish events according to:
a functioning principle;
a type of change that must be signalled;
where they must be applied and what they must control;
the physical characteristics of the environment they must monitor.
2.3.2.1
Button
This is absolutely the easiest detector to use. There are all types available, from those that are activated manually, those that must be
pulled, and those that can be pressed by foot. It is sometimes and extension of a more advanced detector.
2.3.2.2
Magnetic contact (reed)
This contact is used to control the opening of doors and windows. The opening sensor has two parts: a magnet and a blade cont act, or
something similar. When they are placed next to each other, at a distance of a few millimetres, the magnetic field of the mag net keeps
the blade contact in position to close the electrical circuit. Separating them reduces the force of the magnetic field, the blade is no
longer in position, and the electric circuit is broken, generating an opening signal. The magnet is applied to the door or ca sement and
the magnetic contact is applied to the frame, as far as possible from the hinges, so that even slightly opening the door or window may
break the circuit. There are various models available to meet a wide range of aesthetic and technical demands (wooden doors a nd
windows, security doors, sunken contacts, etc.). This detector is used mainly to create perimeter protection.
2.3.2.3
Cable contacts for rollers
The detector is installed inside the roller box. The sensor is an impulse counter that is paired with an automatic cable wind er. By
connecting the end of the thin cable to the lower part of the roller, each time the blind is raised or lowered, the cable winder turns and
generates the impulses detected to the counter. Depending on the number of impulses generated during a specific interval, the
detector can signal an attempted intrusion. This type of detector makes it possible to keep the windows open and the rollers closed to
help air to circulate, thereby guaranteeing perimeter protection.
2.3.2.4
Broken glass detector
This detector can be created using various technologies and exploiting different principles of physics. For example, it can detect the
oscillations caused by the breaking or cutting of glass when it is glued to the glass or crystal to be protected, or detect the characteristic
sound waves generated by glass breaking, when it is positioned in the immediate vicinity. It is used to signal the breaking of shop or
showcase windows, large plate glass windows and skylights for perimeter protection, but also for breaking of bulletin boards and
display cases inside buildings.
2.3.2.5
Vibration detector
Also known as a seismic detector, this device picks up vibrations from the surfaces it is glued or screwed to and filters them to prevent
false alarms. When applied to a door or window, unlike the magnetic contact, it can signal an attempted break-in before the door or
window is actually opened. Indeed, by seeking to force the opening, vibrations are produced that generate a signal of attempted
intrusion.
