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Installing a home intrusion or burglar alarm system offers personal protection and peace of mind. Modern burglar alarm systems provide remote monitoring so you can keep an eye on your home even when you're not there. The home intrusion alarms available today offer many options while also being relatively inexpensive. A system with modest features is better than none at all.
 | Your alarm system can begin as a basic control unit, and you can add features as your needs require and budget allows. |
Comparing intrusion alarms
An alarm system includes these parts:
- The alarm company sign. The most important part is the alarm company sign in your yard, which can deter an intruder.
- The intrusion alarm panel. This is preferably located out of sight. All of the sensors and control keypads are wired to this panel.
- The operations center. This keypad should be in a convenient location. The monitor and control keypad is located near the door you most often use to leave the house. This operations center allows you to arm the system as you leave and set a time delay to disarm the system when you get back (but you can add keypads to other locations).
- The control panel. The center is wired to door, window, and motion sensors and is usually in the basement or a mechanical equipment area. If any of the sensors signals the system, it activates a signal to alert you of the findings. The signal can be audio, visual, or both, and it can be in one or multiple locations. The center can also automatically make phone calls for help. The central control panel should be out of sight and locked.
Intrusion-detection systems can be divided into two basic types:
- Single zone: A typical intruder alarm system consists of one central control unit. These systems usually have a 120-volt power unit and include a battery backup to ensure operation when the power goes out (whether due to natural causes or intruder disconnection). The central unit is wired to sensor switches at doors and windows using two-conductor cable. A single-zone system drawback is that the whole shebang is either enabled or disabled.
- Multiple zone: A security zone is an area you've defined. Larger homes may have six or more unique security zones. You can control each zone independently, depending on its use or need. Turn off the kitchen monitoring if you plan to be in there for a while, but leave the other zones fully armed.
Understanding sensors
Your alarm's control system needs something to monitor, and that something is sensors — the devices that tell the central control system when a door or window has been opened, or when motion has been detected.
Magnetic sensors
Alarm systems use one of two types of magnetic sensors for doors and windows:
- Closed-circuit: Closed-circuit door and window sensors are two-part magnetic switches. The magnet is mounted securely to the window frame or door, which is the moving item. The on/off switch is mounted to the stationary door or window casing. When you open the door or window, the switch opens (breaks contact) and opens a circuit to the central control. This initiates the alarm process, which may include a local alarm, phone dialing, and other actions.
- Open-circuit: These systems also use magnetic sensors at doors and windows, but the circuit closes instead of opening when the door or window opens. If a wire or connection fails on a open-circuit system, you've no way to detect it without testing.
Nonmagnetic sensors
Alarm systems use one of two types of nonmagnetic sensors for doors and windows:
- Button switches: These magnetic switch alternatives are recessed into the doorframe. A ball or probe on the switch face moves back and forth to operate when the door is opened or closed.
- Motion: Detectors for motion come in two flavors:
• Passive Infrared (PIR): You may get a false alarm from this heat detector if you aim it toward heat sources such as ducts or sunlit windows.
• Dual Technology (DT): This type emits high-frequency sound waves that bounce back to the sensor. With those waves it can detect heat and disturbances. Both elements — fluctuating heat and disrupted sound reflection — must be present to trip this alarm.
Wiring and installing sensors
Unless your control-equipment manufacturer recommends otherwise, all of the alarm sensors will be wired using a four-conductor, 22 AWG or heavier, unshielded cable with solid or twisted-copper conductors. The cable should also have a UL Class-2 rating.
Cable from each switch location is a home run directly to the master control unit location. Follow the manufacturer's recommendations for pre-planning, drilling, and installing the wiring. Try to keep the wiring and the switch sensors hidden and protected to increase the alarm's security and reliability.
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