SAFETY : Get Alarmed for Security's Sake

From Associated Press

A burglar alarm can help deter burglars. It can also warn you or your neighbors if someone breaks into your home.

Even the most sophisticated system can give a false alarm, be bypassed by an expert burglar, or be worthless in a home where other precautions aren't taken. Yet of all the security measures you can take, installing an alarm system is the most effective.

To determine which system is best, ask your local police department to conduct a free survey of your property.

You can pay thousands of dollars for a professionally installed burglar alarm system, but most of the cost is for labor. If you're handy, you can install an equally effective system for considerably less.

Basic Equipment

There are two basic systems: perimeter and motion detector. A perimeter system sounds an alarm when someone opens a door or window. A motion detector sounds an alarm when sensors inside the house detect motion. The most effective system often combines the two basic types: magnetic sensors on all the doors and windows and motion-detecting sensors in all crucial spaces near valuables.

Both types consist of sensors connected to a control box, a digital key pad or remote-control key switch to turn the system on and off, and a bell, siren or other warning device. Make sure the switch has a delayed action which will allow you to leave and re-enter the house without sounding the alarm.

Both systems use 12-volt wiring and a transformer to convert 110-120-volt current to 12 volts. Some systems have rechargeable backup batteries to guard against blackouts.

Estimate your needs by drawing a floor plan, showing windows and doors for each room. This will let you easily determine the number of sensors and feet of wire you need for a perimeter system and the best locations for modern decoders. Buy the components at an electronics store or directly from a manufacturer.

Perimeter Systems

A perimeter system protects the boundaries of your home. It sounds an alarm when someone opens a door or window, thus breaking an electric circuit. This system is inexpensive, easy to install, and is a deterrent because it's visible.

A simple perimeter system can be bought in kit form, with a control box, a bell or siren, magnetic sensors, a key pad or remote key switch, and wiring. It detects intrusion instantly. But it requires a lot of wiring since every vulnerable entry must have a sensor.

Magnetic sensors are made up of a magnet and a switch. Install the magnet on a closed door or window and the switch on the frame. As added security, you can install foil tape or vibration detectors on the window panes to guard against glass breaking. Mount the control box in a closet.

Motion-Detector System

These systems require less wiring. They sound an alarm only when an intruder prowls into a monitored indoor space.

A motion-detector system sounds off when motion is detected. This type of system is difficult to spot and elude. But it can be activated by pets, children, or by breezes that cause movement of drapes or curtains.

The sensors in this system might be an electric eye (with infrared beam), ultrasonic (with inaudible sound waves), or passive infrared (body-heat sensitive). Install an electric eye and its reflector across a doorway or corridor a few feet from the ground. Mount other sensors in the corners of rooms near the ceiling, aimed at crucial traffic areas.

You can also install pressure-sensitive mats under rugs by doors and valuable items. When stepped on, these mats will sound the alarm.

Rig the switch for either system near the entrance so that you can quickly disarm the system when you enter. Mount the bell or siren on the outside of the house at least 10 feet above the ground.

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