Alarm Intruder Views

General Goods

Now I can create a function that tests and acts on the result of the scene changes. If the size of the biggest change is more than 1,000 pixels, then we will call that an intruder event, and we will use the SendMail command to send me email to tell me about it together with the highlighted changed image. I ignore the case of over 70,000 pixels, as I don ’t want an alarm when someone turns off the office lights and the entire image changes.

A taut wire perimeter security system is basically an independent screen of tensioned tripwires usually mounted on a fence or wall. Alternatively, the screen can be made so thick that there is no need for a supporting chainwire fence. These systems are designed to detect any physical attempt to penetrate the barrier. Taut wire systems can operate with a variety of switches or detectors that sense movement at each end of the tensioned wires. These switches or detectors can be a simple mechanical contact, static force transducer or an electronic strain gauge. Unwanted alarms caused by animals and birds can be avoided by adjusting the sensors to ignore objects that exert small amounts of pressure on the wires. This type of system is vulnerable to intruders digging under the fence. A concrete footing directly below the fence is installed to prevent this type of attack.

A fibre-optic cable can be used to detect intruders by measuring the difference in the amount of light sent through the fibre core. If the cable is disturbed, light will ‘leak’ out and the receiver unit will detect a difference in the amount of light received. The cable can be attached directly to a chainwire fence or bonded into a barbed steel tape that is used to protect the tops of walls and fences. This type of barbed tape provides a good physical deterrent as well as giving an immediate alarm if the tape is cut or severely distorted. Other types work on the detection of change in polarization which is caused by fiber position change.

Monitored alarms and speaker phones allow for the central station to speak with the homeowner and/or intruder. This may be beneficial to the owner for medical emergencies. For actual break-ins, the speaker phones allow the central station to urge the intruder to cease and desist as response units have been dispatched.