Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, September 20, 1994 TAG: 9409230009
SECTION: EXTRA PAGE: 3 EDITION: METRO
SOURCE: David Butler
DATELINE: LENGTH: Medium
A: Most home security systems are designed to detect an intruder only after your home has been violated. Notwithstanding the effect of deterrence, a window or door sensor can't do much to keep someone out of your home. For the best possible protection, you should augment your existing alarm system with outdoor sensors and high-wattage security lighting. And don't underestimate the importance of high-quality window and door locks.
Several types of sensors are available for protecting your property's outer perimeter: photoelectric beams, buried magnetic and seismic sensors, microwave beams, shock detectors and passive infrared detectors. Because of their high cost, microwave and seismic sensors are rarely used in residences.
Photoelectric beams, one of the most reliable and popular methods for perimeter protection, can be used to create an invisible fence around your home. Each corner consists of one transmitter and one receiver unit, usually mounted on a post. Although small animals can pass under a properly aligned PE beam, dogs and other large animals will be detected, as will people.
If your property is fenced in, you can install a shock sensor on each entrance gate. A wireless model is available that boasts a range of up to 300 feet. The receiver/sounder simply plugs into an electrical outlet inside your home. Shock sensors can also be used to monitor a mailbox, an out-building or a fenced-in swimming pool.
Because outdoor sensors can't distinguish friend from foe, your alarm system should not be allowed to take preemptive action in response to an outdoor perimeter violation. An indoor alert or chime is more appropriate.
Perimeter sensors can also be tied to outdoor security lights. However, an intruder is likely to flee as soon as the lights come on. I prefer to switch on the lights manually after I'm in position to view the area. Otherwise, I may never know who or what triggered the alert.
If you simply want to be alerted to approaching vehicles, you should consider a driveway alert system. One type uses a magnetic sensor that's buried alongside or beneath the driveway. The sensor detects vehicles that pass within its 15-foot range. If burying cable is not your cup of tea, you can opt for a wireless driveway alert. Several models are available that rely on easy-to-install motion sensors.
Most people are familiar with the motion-activated floodlights sold in home centers. When anything passes through their coverage zone, the lights turn on for a preset interval. However, there's no signal inside the house let you know the detector has been tripped.
One unique security light solves this problem with power line carrier technology. It broadcasts a signal over the electrical wiring whenever something trips the motion detector. This signal can be used to activate a variety of receivers, including an inexpensive chime module.
To receive a list of companies that manufacture photoelectric beams, driveway alerts and other outdoor security sensors, please send $1.50 and a self-addressed envelope to David Butler F-418, Department TWN, 14713 Pleasant Hill Road, Charlotte, N.C. 28278-7927. The list includes toll-free phone numbers and a summary of each company's products. You'll also receive sources for motion-activated floodlights.
Q: I've just started using power line carrier modules and controllers. Could you please explain the difference between an appliance module and a lamp module?
A: Lamp and wall-switch modules are dimmable and therefore should only be used to control lights. Appliance modules and receptacles instead have a mechanical relay. They can switch any electrical load rated at up to 15 amps.
by CNB