Motion detection systems detect movement in areas covered by the security sensors.
Some motion detection systems transmit high frequency radio wave signals into
the secure area of a room or hallway. Other systems may use infrared light to
detect heat changes, such as when a person (body heat) walks by the infrared sensors.
If a person moves in the range of the motion sensors, the alarm (audible,
visual, or silent) is activated.
Some motion detection systems use
lasers and photoelectric beams. The laser is a light beam shot across to the other
side of the room, doorway or passageway. If this light beam is interrupted
the unit's alarm signal is activated. Other motion detecting systems detect vibration.
Many car alarms have this feature to alert the owner that something has
bumped into his automobile or somone has broken into it.
Outdoor motion
detecting systems are often used to monitor driveways and work when movement
causes floodlights to illuminate an area of the driveway. They usually use
an infrared detection sensor which senses temperature changes. Unfortunately, squirrels,
cats and sudden wind gusts can turn the lights on and off repeatedly,
which makes them annoying to many homeowners. |
