page_title: Security alarm
section_title: Design
hierarchical_section_title: Security alarm / Design
caption_attribution_description: English: A Klaxon Flashguard external alarm bell box mounted on the front of a house in the UK. This is the warning device used in addition to a burglar alarm system to alert that an alarm event has occurred on the premises. This is a audio/visual deterrent in the act to prevent burglaries. They have comfort lights which are constantly flashing to alert intruders that the system is a live and working system. They also have a strobe flasher which flashes when the alarm is in an alarm condition. The units have a sound output ranging from 105db to 118db. The Klaxon Flashguard unit displayed has a sound output of 118db.
context_page_description: A security alarm is a system designed to detect intrusion – unauthorized entry – into a building or other area such as a home or school. Security alarms are used in residential, commercial, industrial, and military properties for protection against burglary or property damage, as well as personal protection against intruders. Security alarms in residential areas show a correlation with decreased theft. Car alarms likewise help protect vehicles and their contents. Prisons also use security systems for control of inmates.
  Some alarm systems serve a single purpose of burglary protection; combination systems provide both fire and intrusion protection. Intrusion alarm systems may also be combined with closed-circuit television surveillance systems to automatically record the activities of intruders, and may interface to access control systems for electrically locked doors. Systems range from small, self-contained noisemakers, to complicated, multirally systems with computer monitoring and control. It may even include two-way voice which allows communication between the panel and Monitoring station.
context_section_description: The most basic alarm consists of one or more sensors to detect intruders, and an alerting device to indicate the intrusion. However, a typical premises security alarm employs the following components:
  Premises control unit (PCU), Alarm Control Panel (ACP), or simply panel: The "brain" of the system, it reads sensor inputs, tracks arm/disarm status, and signals intrusions.  In modern system, this is typically one or more computer circuit boards inside a metal enclosure, along with a power supply.
  Sensors: Devices which detect intrusions.  Sensors may be placed at the perimeter of the protected area, within it, or both. Sensors can detect intruders by a variety of methods, such as monitoring doors and windows for opening, or by monitoring unoccupied interiors for motions, sound, vibration, or other disturbances.
  Alerting devices: These indicate an alarm condition.  Most commonly, these are bells, sirens, and/or flashing lights.  Alerting devices serve the dual purposes of warning occupants of intrusion, and potentially scaring off burglars. These devices may also be used to warn occupants of a fire or smoke condition.
  Keypads: Small devices, typically wall-mounted, which function as the human-machine interface to the system. In addition to buttons, keypads typically feature indicator lights, a small multi-character display, or both.etc.
  Interconnections between components. This may consist of direct wiring to the control unit, or wireless links with local power supplies.
  In addition to the system itself, security alarms are often coupled with a monitoring service. In the event of an alarm, the premises control unit contacts a central monitoring station. Operators at the station see the signal and take appropriate action, such as contacting property owners, notifying police, or dispatching private security forces. Such signals may be transmitted via dedicated alarm circuits, telephone lines, or the internet.
caption: Exterior alarm bell box
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