Home burglar alarms were once only found on houses of the rich & famous. In recent years, however, they are becoming more and more common in the homes of "Joe Average".

Many people choose a simple do-it-yourself security system. These systems can be either wired or wireless and will set off an audible alarm when an intruder breaks in or when they are moving in the house.

There are two types of burglar alarms - open or closed circuit. With an open circuit alarm system the alarm is set off when the circuit is closed. When a door or window is opened, it completes the circuit and sets of the alarm. A closed circuit system works in the opposite way - when a door or windows is opened, it breaks the circuit and sets off the alarm.

Motion sensors are a slightly more sophisticated option. They sense motion within a certain field around the sensor. When motion is sensed, a signal is sent to the control panel which analyzes it to see if it is enough movement to be suspicious.

The sensitivity of these motion sensors can be adjusted to account for things like air movement that might rustle papers or pets walking around the house.

Ideally, it's best to use both magnetic switches and motion sensors in a burglar alarm setup. The switches protect doors and windows and motion sensors make it easier to protect large spaces like halls and large rooms.

Another option that many people use is video cameras. The cameras are mounted in such a way as to "see" strategic areas around the house. The images they pick up are displayed on a monitor inside the house, and may be recorded on videotape.

Most home security companies also provide remote monitoring of their alarm systems. If the alarm is tripped the security company will alert the police or may send its own security personnel to the home.

Four of the most popular types of burglar alarm systems include:

1. Single premise alarm systems

These systems are meant to provide protection against specific things, which include door alarms (to warn you if a door is opened), carbon monoxide alarms, heat/smoke detectors, etc.

2. Local alarm systems

These systems will sound an alarm in case of intrusion, but they are not monitored by an outside company.

3. Telephone dialer alarms

These systems will dial a specific phone number if the alarm is tripped. They may also be able to dial multiple numbers and will generally play a pre-recorded message when the call is answered.

4. Monitored security systems

These are the most effective systems because they are constantly monitored by the alarm company. If the alarm is tripped, a signal is sent to the monitoring station and they can follow up by calling the police or sending their own personnel to the home.