Burglar alarm control panel
Encyclopedia
A burglar alarm control panel is a wall-mounted unit where the detection devices and wiring of the alarm are ultimately connected and managed. These include devices such as bells, sirens
, door contacts, motion detector
s, smoke detector
s, etc. Typical panels are located in utility closets or access rooms.
. In this type, the sensor circuit (called the loop
in industrial terminology) holds the relay energized. Since the path for the loop goes through a set of contacts which are normally open (when the relay is restored they are open, when the relay is energized they are closed), when the loop opens, even momentarily, the relay will drop out and stay that way. A second set of contacts on the relay, normally closed (when the relay is restored they are closed, when the relay is energized they are open) is used to operate the annunciator, usually a bell. The system is disarmed by a key-operated shunt which forces the relay to energize, and is armed by closing all traps and then by opening the shunt. While burglar alarm controls are now very elaborate, the single-relay control incorporates all the functionality of any control. These controls and a closely related dual-relay design are still widely used in stand-alone applications, powered by lead-acid batteries.
s when inactive and double the value when active. This wiring system is called dual loop
and allows for both alarm and anti-tamper detections to be incorporated into one circuit (anti-tamper occurs when the resistance level moves outside normal open/close values). This is the standard circuit in most modern systems.
which sends operating information to the control. Thus, there is no point in attacking the keypad, as there is no intelligence in the keypad, it is all located in the control. Also, many controls feature integrated transmitters, using wired telephony or optionally, cellular telephony. These controls also monitor the status of the telephone line
, and can be programmed to trip if the telephone line fails (or is cut). The controls which utilize cellular telephony report either periodically or at a pseudo-random interval to the central station, and a failure to report will result in a dispatch.
High-security alarm controls use current and impedance monitoring on the premises, and may report to the central station via dedicated voice-grade or DC (obsolescent) circuit, or by means of multiple-drop AC grade transmitter (multiplex).
Siren (noisemaker)
A siren is a loud noise making device. Most modern ones are civil defense or air raid sirens, tornado sirens, or the sirens on emergency service vehicles such as ambulances, police cars and fire trucks. There are two general types: pneumatic and electronic....
, door contacts, motion detector
Motion detector
A motion detector is a device for motion detection. That is, it is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices that alert the user of the presence of a moving object within the field of view...
s, smoke detector
Smoke detector
A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector...
s, etc. Typical panels are located in utility closets or access rooms.
Overview
The simplest type of burglar alarm control consists of a single relayRelay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...
. In this type, the sensor circuit (called the loop
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
in industrial terminology) holds the relay energized. Since the path for the loop goes through a set of contacts which are normally open (when the relay is restored they are open, when the relay is energized they are closed), when the loop opens, even momentarily, the relay will drop out and stay that way. A second set of contacts on the relay, normally closed (when the relay is restored they are closed, when the relay is energized they are open) is used to operate the annunciator, usually a bell. The system is disarmed by a key-operated shunt which forces the relay to energize, and is armed by closing all traps and then by opening the shunt. While burglar alarm controls are now very elaborate, the single-relay control incorporates all the functionality of any control. These controls and a closely related dual-relay design are still widely used in stand-alone applications, powered by lead-acid batteries.
Modern panels
Modern alarm controls are solid-state devices, and do not use the relays that the older alarm panels used to go into alarm. They make use of relays to modulate the alarm notification device as needed. And they use a relay to seize the telephone line to communicate to the monitoring station. Most switching devices are N.C. (normally closed) circuits, so when the device is not in an alarm condition, the circuit is closed. Most alarm circuits (zones) are also set up to open or close on reading a certain resistance, usually between 1K and 5K ohmOhm
The ohm is the SI unit of electrical resistance, named after German physicist Georg Simon Ohm.- Definition :The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere,...
s when inactive and double the value when active. This wiring system is called dual loop
Dual loop
This article refers to the electrical circuit as used in burglar alarms. Several other uses for the term "Dual loop" may also exist.Dual-loop is a method of electrical circuit termination used in electronic security applications, particularly modern intruder alarms. It is called 'dual-loop' because...
and allows for both alarm and anti-tamper detections to be incorporated into one circuit (anti-tamper occurs when the resistance level moves outside normal open/close values). This is the standard circuit in most modern systems.
Summary
Early (c.a. 1980) solid-state alarm controls used shunt switches or momentary closures on the key circuit to arm or disarm the control. Modern controls can use these arming techniques, but more frequently use a keypadKeypad
A keypad is a set of buttons arranged in a block or "pad" which usually bear digits, symbols and usually a complete set of alphabetical letters. If it mostly contains numbers then it can also be called a numeric keypad...
which sends operating information to the control. Thus, there is no point in attacking the keypad, as there is no intelligence in the keypad, it is all located in the control. Also, many controls feature integrated transmitters, using wired telephony or optionally, cellular telephony. These controls also monitor the status of the telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
, and can be programmed to trip if the telephone line fails (or is cut). The controls which utilize cellular telephony report either periodically or at a pseudo-random interval to the central station, and a failure to report will result in a dispatch.
High-security alarm controls use current and impedance monitoring on the premises, and may report to the central station via dedicated voice-grade or DC (obsolescent) circuit, or by means of multiple-drop AC grade transmitter (multiplex).