Burglar alarms can deter burglars and warn you or your neighbors if someone breaks into your home. You can pay thousands of dollars for a burglar alarm system, but you'll be paying mostly for labor. If you're handy, you can install an equally effective system yourself for a fraction of the cost.

Types of burglar alarmsThere are two types of do-it-yourself systems: perimeter and motion-detector.

- A perimeter system protects the boundaries of your residence. The alarm is activated by a break in an electric circuit when someone opens a door or window. A perimeter system is inexpensive and easy to install. It is also an effective deterrent, because it is visible. However, it can be penetrated by an expert burglar. Perimeter systems require a lot of wiring, which for esthetic and safety reasons must be hidden under moldings or snaked through the walls.

- A motion-detector system sounds an alarm when sensors inside the house detect motion. Infrared beams, electric eyes, ultrasonic waves, special microphones and pressure-sensitive mats are some of the sensing devices used in this system.

Motion detection systems have the advantage of being difficult to spot and elude. However, they can be activated accidentally by pets, children or even by breezes from a fan or air conditioner which cause movement of drapes and curtains.

The most effective burglar alarm system combines the two types: a perimeter system on all entry doors and windows, and motion detecting sensor in all other crucial spaces.

Basic equipment

Along with sensors, both types of alarm systems have a control box, a remote-control switch to turn the system on and off, and a ball, siren, or other warning device.

The remote-control switch may be digitally or key activated. Digital activation lets you periodically change the combination that unlocks the switch. Either system should have delayed action to give you enough time to enter the house and turn off the switch without sounding the alarm.

Mount the control box in a closet and rig the switch near the entrance so that when you enter you can quickly disarm the system.

You an install a panic button in the bedroom so you can sound the alarm if you detect a prowler at night.

Some systems have a backup battery to guard against power failures.

Installation tips

Alarm systems can be purchased at an electronics store or directly from the manufacturer. A simple perimeter system can be bought in kit form, with control box, bell or siren, magnetic sensors, remote key switch, and wiring. Panic buttons and additional sensors can be added separately.

Estimate your needs by drawing a floor plan of your residence, showing windows and doors for each room. Include windows and exit doors in a basement or attached garage.

Installing a perimeter system

1. The sensors on a perimeter system consist of a magnet plus a magnetically activated switch. Install the magnet on a closed door or window and the switch on the frame. If possible, recess them in the wood so that they cannot be seen from the outside.

2. Following the manufacturer's instructions, wire the sensor switch top to the control box. Each detector also needs a shunt switch that allows you to disconnect it when you want to open the door or window without shutting off the entire system.

3. To guard against window breaking, install aluminum foil strip or vibration detectors on the glass panes.

Installing a motion-detector system

The sensors in a motion-detector system might be electric eye (with infrared beam), ultrasonic (with inaudible sound waves) or passive infrared (body-heat sensitive).

1. Following the manufacturer's instructions, 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 the room near the ceiling, aimed at crucial traffic areas.

2. Install pressure-sensitive mats under rugs by doors and valuable items. When stepped on, these mats will sound the alarm.