3.0—Home Security and Surveillance Systems
3.0—Home Security and Surveillance Systems
3.0—Home Security and Surveillance Systems
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140<br />
Chapter<br />
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3<br />
Motion Detectors<br />
Motion detectors work by detecting the changes in the infrared energy in<br />
an area. Because these devices do not emit any energy, they are called<br />
passive infrared (PIR) detectors. PIR detectors use a lens mechanism in the<br />
sensor housing to detect a change in infrared energy across the horizontal<br />
sectors covered by the sensor. This type of detector is insensitive to stationary<br />
objects but reacts to rapid changes that occur laterally across the<br />
field of view. They are the most common <strong>and</strong> economical type of motion<br />
detectors <strong>and</strong> are available in st<strong>and</strong>ard, pet-friendly, <strong>and</strong> harsh-environment<br />
(outdoor) models. An example of a motion detector for interior use is<br />
shown in Figure 3.4.<br />
Figure 3.4 Motion detector.<br />
<strong>Security</strong> Panels<br />
<strong>Security</strong> panels provide several functions to coordinate the operation <strong>and</strong><br />
management of a security system. They can include an integrated keypad or<br />
LED indicators. Most designs include a power transformer for converting<br />
the AC voltage to a DC voltage for the sensor loop <strong>and</strong> contain a rechargeable<br />
battery for backup if the commercial power fails. A terminal strip provides<br />
for the connection of the wiring that connects all the sensors to the<br />
controller as well as the external telephone line. Most designs include a<br />
printed circuit board containing all the electronics <strong>and</strong> a microprocessor. It<br />
also connects to <strong>and</strong> controls the siren that is activated when an alarm condition<br />
exists.<br />
<strong>Security</strong> panels are known by numerous names, such as central control box, control panel,<br />
alarm panel, <strong>and</strong> interface panel. They all perform similar functions including controlling <strong>and</strong><br />
monitoring sensor status, providing power to the system, connecting the telephone line to the<br />
monitoring station, <strong>and</strong> h<strong>and</strong>ling the programmable options for the system.