Sensors in the Home or Office

• Alarm systems use a variety of methods to detect unlawful entry. Doors and windows have electronic contacts that trigger an alarm if separated. Motion detectors can sense movement in specific locations. Alarms can even be configured to only activate certain triggers, such as motion detectors, when the occupants are away, while continuing to keep external doors and windows active.
  
  

Alerting the Police

• When a security system is triggered, not only is a loud alarm usually sounded, an electronic signal is also sent to a central monitoring office, usually located hundreds or thousands of miles away. The idea is that most people in earshot of the alarm will take little or no action simply based on the alarm itself. False alarms on cars, homes and offices are so common, the argument goes, that depending on neighbors or passersby to alert the police is unreliable at best. So, for a monthly fee, the central monitoring office will alert police themselves.
  
  First, though, a call is usually placed to the home or office where the alarm is triggered. This gives the occupants there the opportunity to defuse the situation if it's indeed a false alarm. If the phone is not answered, or it it is answered in distress, the police are immediately notified and dispatched.
  
  

Costs

• Alarm monitoring is a lucrative business. The cost of monitoring the alarm system and placing the occasional phone call is far exceeded by the monthly fee the companies charge. However, calling police officers to a home takes them away from other responsibilities. It costs money for the officers' time responding to and reporting on the incident, and to fuel their transportation. The cost to respond can be up to $50 per alarm, but these costs are not borne by the monitoring agency -- they are paid from the taxes of not just the property owner, but all individuals and companies paying local taxes.
  
  Almost 99 percent of all alarms turn out to be false. The cost of responding to each and every one can get so high that most police force will charge the property owner for excessive alarms. However, the monitoring companies themselves have no cost incentive to limit false alarms. As a result, many of their clients choose to discontinue monitoring service and hope the signs and sounds of an otherwise disabled alarm will provide peace of mind and work as a deterrent to thieves and vandals, instead of continuing to allow a distant private company to capitalize on the response of their publicly subsidized local police force.