There are many types of intrusion detection systems (passive and active infrared sensors, vibration sensors, glass shatter sensors, radar sensors, ultrasonic sensors, magnetic contacts, ground detection sensors, fence detection, laser sensors etc.)
The simplest alarm consists of one or more sensors for detecting intruders and a warning device to indicate the intrusion. However, a typical space security alarm uses the following components:
- The space control unit (PCU), the alarm control panel (ACP) or simply the panel: the “brain” of the system reads the sensor inputs, monitors the status of the arm / disarm and signals inputs. In a modern system, it is usually one or more computer circuit boards inside a metal enclosure, along with a power supply. Many newer systems often use sealed outdoor plastic boxes. Some also have control units built into the keyboard or other human-machine interface.
- Sensors: Devices that detect intrusions. The sensors can be located at the perimeter of the protected area, inside it or both inside and at the perimeter. Sensors can detect intruders through a variety of methods, such as monitoring the opening of doors and windows or by monitoring unoccupied interiors for movement, sound, vibration or other disturbances.
- Warning devices: these indicate an alarm status. Most commonly, these are bells, sirens and/ or flashing lights. The warning devices have the dual purpose of alerting occupants on the intrusion and scaring off potential burglars. These devices can also be used to warn occupants of fire or smoke.
- Keyboards: small devices, usually mounted on the wall, that function as a human-machine interface with the system. In addition to buttons, keyboards usually have indicator lights, a small multi-character display, or both.
Interconnections between components may consist in direct wiring to the control unit or wireless connections to local power supplies.
The trigger signal from each sensor is transmitted to one or more control units either by wires or by wireless means (radio, line carrier, infrared). Wired systems are convenient when sensors (such as PIRs, smoke detectors, etc.) require external power to function properly; however, they can be more expensive to install. Input-level wired systems use a stellar network topology, in which the panel is logically centered, and all devices at home run their line wires back to the panel. The more complex panels use a bus network typology in which the wire is practically a data loop around the perimeter of the installation and has drops for the sensor devices which must include a unique device identifier integrated in the sensor device itself.igger signal