Dating back to his eviction from the Garden of Eden, man has used any available means to protect himself, his family and his possessions. Early man found shelter in primitive huts, crude tents or caves. Weapons were fashioned, and dogs were domesticated to protect against predatory neighbors.
Early societies were formed primarily to provide mutual protection through strength in numbers. As these societies grew, and man developed more sophisticated weapons, more elaborate defenses were needed.
Eventually, walled cities were protected by professional armies, which also enforced laws and kept the peace. Meanwhile, families continued to use dogs, geese and other animals to warn of intruders.
It seems amazing that despite great social upheavals and scientific breakthroughs, we still must protect ourselves and our property from thieves and attackers. We haven’t done away with the criminal element, unfortunately, but we have developed effective security barriers, locks and alarm systems.
In fact, it’s now a difficult task just to sort through the various security devices available. This month, we’ll talk about equipment best-suited for residential security systems. We’ll save a discussion of locks, doors and barrier devices for a future column.
Selecting a home security system involves identifying appropriate components and installing them properly. Alarm sensors can be categorized as “perimeter” and “interior”.
Perimeter sensors include door and window contacts, acoustic discriminators and photo-electric beams.
Door and window contacts are simple “balanced magnetic” switches; one magnet attaches to the door and one to the frame to complete an electric circuit.
Acoustic discriminators sound when exposed to high-frequency sound waves produced by breaking glass. Photo-electric beams are invisibly projected across open areas; an interrupted beam announces an intrusion.
Among available interior sensors are ultrasonic motion detectors, passive-infrared motion detectors, microwave beams, dual-technology motion sensors and electro-magnetic proximity sensors. (And you thought it would be easy to find something that “works”.)
Ultrasonic motion detectors emit sound waves that deflect off walls, floors and ceilings; when disrupted, an alarm sounds. Microwave beam sensors operate similarly, but the beam does not necessarily stop at the building walls. This extra sensitivity can trigger false alarms when the device detects objects moving outside.
Passive-infrared motion sensors emit beams reflected back to the sensor at an accepted intensity, triggering an alarm when the beam’s intensity is disrupted. Like the microwave sensor, ultrasonic and passive-infrared sensors tend to produce false alarms under certain circumstances. (Let’s face it: All systems trigger false alarms under certain circumstances.)
To minimize false alarms, dual-technology sensors were developed, combining two technologies into a single device. To trigger an alarm, both sensor mechanisms must sense the event. Dual-event, passive-infrared systems also are available to reduce false alarms.
Electro-magnetic proximity sensors can be utilized to protect safes, jewelry boxes and other valuables. These sensors produce an electro-magnetic field around valuable, sounding an alarm when interrupted.
Most systems are installed with wire-lines connecting sensors to a central processing unit, but effective wireless systems also are available. A good wireless system may cost a little more to install than a wireless system, but it’s less likely to be damaged if the home or nearby utility pole is struck by lightning.
A “top-of-the-line” home security system might include a photo-electric beam system around the outer property line that, when interrupted, would automatically turn on outer porch and yard lights. Doors and windows would have sensor contacts, and acoustic discriminators would be located near sliding glass doors or large windows.
Dual-technology or dual-event motion sensors would cover interior rooms and hallways, and valuables would be stored in a safe protected by an electro-magnetic proximity sensor. Smoke sensors (for fire protection) also might be installed in the kitchen.
Each of these devices would be centrally monitored, via dedicated telephone line, by a central monitoring station capable of contacting police or fire departments after receiving an alarm.
Of course, most of us can’t afford (and probably don’t need) such an elaborate system. So, what do the rest of us need?
Well, each of us should install at least one-dual-technology or dual-event motion sensor covering the area most likely to be crossed by an intruder. You should have contact sensors on all accessible first-floor windows and doors. And you should install a smoke sensor in the hallway and heat sensor in the kitchen.
These sensors should be monitored by a central station for maximum protection. Several reputable companies provide effective monitoring service for a monthly service fee.
In Dallas, you must obtain a permit for your alarm system. If you don’t, the city can charge you $50 for each false alarm. Most security companies will help you fill out the appropriate paperwork.
It’s important to remember, of course, that no security system is effective unless it is regularly utilized.
Now that we’ve briefly discussed the technological advances in security systems, I’d like to mention the most effective alarm system available today: a great big dog.
As they say, the more things change, the more they remain the same.
