Security systems have long been an important residential technology, and home control has remained relatively popular since the 1980s. This article, the last of 12 parts, covers the basics of home control, and then moves on to the design considerations for intrusion detection systems — burglar alarm technology.


The appeal of home-control systems comes from their ability to improve a person's lifestyle. This is the reason why homeowners are interested in them, and why home builders want to offer them to their customers.

Home-automation systems are completely flexible devices; they don't force people into any one pattern of living and will do whatever you tell them to do. They are completely agreeable to your likes, dislikes, tastes and personality.

The systems give the homeowner great flexibility and control. (For example, they can allow you to turn on your bathwater over the phone before you leave the office).

A properly designed home-automation system will also save a good deal of money in utility bills, often paying for itself quickly. These special control systems deliver entertainment and communications better than regular telephone, TV and stereo systems alone. They can also do exotic things, such as turn anything on or off upon voice commands only. You can set sequences of operations (lighting or sound for various situations) simply by speaking a command into the air. The possibilities are endless.


Before you can begin automating any home, old or new, you need to know the basics of home automation systems. A home control system has four basic parts:

  1. The central controller. This is a control unit that contains the “brains” of the system. For basic systems, this is a table-top device, appearing similar to a clock-radio. Complex systems use a computer as a central controller. (The computer can usually be used for other things also, not only as a central controller.)

  2. A means of communication between the various parts of the system. This can come in numerous forms: Copper wires, radio communication, infrared light or signals sent over power lines.

  3. Sensors. Many different types of sensors monitor all sorts of conditions. These would include thermostats, electrical sensors, light sensors or humidity sensors.

  4. Actuators or “action-makers.” These are the parts of the system that make something happen. These would include such things as motors, valves, relays or anything else that causes an action.

All of these four parts working together are what make the system capable of controlling the home. The sensors give notice to the central controller of certain conditions (window open or temperature), the controller compares these conditions with its program, and the correct signals (if any are required) are sent to the actuators.


In recent years, home automation and security systems have begun to overlap with each other. Wireless security components and RF home automation components are very similar. In fact, the only substantial difference between home automation controls and security controls is the supervision capabilities built into most security systems.

When these two types of systems are combined, they can be used creatively to provide not only intrusion detection, but also intrusion prevention. This is done through long-range outdoor detection of persons or vehicle, and the use of lighting, or even audio warnings.


All intrusion systems, regardless of how simple or complex, can be divided into three basic parts. Notice how similar these are to those of home automation systems.

  1. Sensors. These devices sense or respond to certain conditions in and around the protected area. (Several types of sensors are used for many different applications.)

  2. Controls. As the brains of the system, these controls respond to the input from the sensors according to the desires of whoever set the system up.

  3. Signaling devices. These devices give out some type of signal (most typically a siren or buzzer) when an alarm condition is reached.


The following sections cover a variety of design suggestions. You may not need to follow all of these suggestions, but they will give you a lot of good ideas, and will also help you direct your thinking about your system.


Intrusion detection alarm systems are used to accomplish one or more of the following:

  • Economize — permit more economical and effective use of manpower by requiring smaller guard forces instead of larger numbers of personnel for patrols.

  • Substitute — use in place of other physical security measures, which cannot be used because of safety regulations, operational requirements, appearance, layout, cost or other reasons.

  • Supplement — provide additional controls at critical points or areas.


The following are some basic principles upon which intrusion detection systems operate:

  1. Breaking an electrical circuit.

  2. Interrupting a light beam.

  3. Detecting sound.

  4. Detecting vibration.

  5. Detecting motion.

  6. Detecting a change in capacitance due to penetration of an electrostatic field.


The following factors need to be considered to determine the necessity and feasibility of installing an intrusion detection system:

  • Mission of the installation or facility.

  • Criticality of the installation or facility.

  • Vulnerability of the installation or facility.

  • Accessibility to intruders.

  • Location of an installation or facility (geographical) and locations of areas to be protected inside the installation.

  • Construction of a building.

  • Hours of operation.

  • Availability of other forms of protection.

  • Initial and recurring cost of the system as compared to cost, in money or security, of possible loss of materials or information.

  • Design and salvage value of the system.

  • Response time by the security force.

  • Savings in manpower and money over a period of time.

  • Intruder time requirement.


Each type of intrusion detection system is intended to meet a specific type of problem. The factors, which should be considered in selecting the appropriate components and system, include the following:

  • Location and response time capability of security personnel.

  • Value of facility, material or the sensitivity of material to be protected.

  • Area environment, to include building construction, sound levels inside and outside or climate.

  • Radio and electrical interference.

  • Operational hours of the installation or facility.

  • Specific target to be protected.

  • Availability of security personnel.

A consideration of these factors indicates the advisability of obtaining technical data to assist in making a wise selection. Often more than one type of sensor, or even system is necessary to give adequate protection for an area or structure. Check with persons already using such systems or devices before purchasing your own whenever possible.