Control Panel Functional Design Specifications
The Intruder Alarm control panel is an enclosure that contains all the electronic components, wire termination points, backup battery packs, and telephone termination wiring.
Each sensor receives power and is managed from the control panel. It monitors the health and operating status of the total system and sends a signal to the siren when an alarm condition exists. The panel should be mounted in a location that is out of plain view and near a 220VAC outlet where a plug-in transformer can be used to supply low-voltage power to the total system. If a phone line is planned for connection to an external monitoring facility, access to the location where the phone line enters the home must be considered when locating the control panel. Preferred locations are utility rooms, basements, and closets.
Keypad Functional Design Specifications
The best location for a keypad is an area that is both convenient to the family users and secure for the system. The homeowner must ultimately determine how many keypads are desired and where they are to be located in the home. Typically, keypads are placed at the main entry/exit door, in the master bedroom, or in the main hallway of the home. In a multilevel home, keypads are commonly placed on each level.
Keypads
The keypad is the device used by the home residents to initiate commands for control options and observe the status of the security system. It usually contains an alphanumeric keypad and LED or LCD displays that indicate the status of the alarm system.
The keypad is used to arm and disarm the system and often includes a panic switch by which the alarm can be triggered instantly in an emergency situation. The alarm can be silenced by the owner by entering the correct coded sequence of numbers on the numerical keypad. The keypad is typically installed inside the home near a door that is most frequently used by the residents. A programmed delay is included as a feature of most systems to enable the users to enter and disarm the system within a fixed delay period (normally 30–45 seconds). The same fixed delay is also used to allow the user to arm the system and exit the home within the fixed delay period. Keypads can also be used to bypass certain areas.
NOTE: The bypass function is used to arm the system but disable selected zones or motion detectors inside the home when the family is present. Residents often desire to secure the perimeter area of doors and windows after retiring for the evening but need to bypass interior area motion detection sensors that are activated only when the home is not occupied.
Sensors
Sensors are designed to protect both the perimeter and the open spaces inside the home. As mentioned earlier, perimeter devices primarily protect doors and windows. The most common perimeter sensors are magnetic door switches, window vibration detectors, and window acoustical detectors. Space protection sensors called motion detectors cover interior rooms and hallways and can detect an intruder who has been able to defeat a perimeter device. Exterior motion detectors and motion-activated security lights are also used. The following paragraphs describe the types of sensors required in basic home security and surveillance systems.
Door Switches
Door switches work on a basic principle of a two-part magnetic switch. A switch that is sensitive to a magnetic field is mounted on the fixed structure (frame), and wires from the switch are routed through the wall to the control panel. A magnet is mounted on the door in a position where it is in close proximity to the switch when the door is closed; this also keeps the switch closed. Opening the door moves the magnet away from the switch and causes the switch to “open,” which is sensed by the central control panel and activates an alarm. Magnetic switches are available as normally open (NO) or normally closed (NC) to accommodate different wiring designs and controller options.
Security system magnetic switches are designed for both normally closed (NC) and normally open (NO) options. An NC switch opens when the magnet is moved near the switch, and an NO switch closes when the magnet is moved in close proximity to the switch. This enables magnetic sensor-type switches to be used with various types of security system designs. Sensor door switches wired in parallel use NO contacts so that any closure of the contacts in the circuit activate an alarm condition. Series circuits use NC magnetic switches where any opening of a switch results in an open condition for the circuit, which triggers an alarm condition by the controller.
Window Acoustic and Vibration Detectors
Window sensors are used to detect the sound of breaking glass. Large glass doors such as patio doors are usually protected by magnetic switches. Windows in the home can also be protected by magnetic switches if they can be opened; however, glass break detectors are recommended by most home security contractors to protect against an intruder entering through a broken window.
Glass break detectors are available in either vibration type or acoustical type. The vibration type is mounted on the glass or on a nearby wall.
Motion Detectors
Motion detectors work by detecting the changes in the infrared energy in an area. Because these devices do not emit any energy, they are called passive infrared (PIR) detectors. PIR detectors use a lens mechanism in the sensor housing to detect a change in infrared energy across the horizontal sectors covered by the sensor. This type of detector is insensitive to stationary objects but reacts to rapid changes that occur laterally across the field of view. They are the most common and economical type of motion detectors and are available in standard, pet-friendly, and harsh-environment (outdoor) models.
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