Basic Alarm System Terminology

Access Code/User Code – A four-digit (usually) code that allows a user to turn an alarm system on (Arm) or off (Disarm). It may have other permitted functions, but usually cannot do things like change access codes or access programming modes.

AHJ/Authority Having Jurisdiction – The local authority that has jurisdiction concerning the operation and installation of alarm systems. Some locations regulate security and/or fire alarms more stringently than others.

Arm – To turn the security system on. In general, all zones have to be secure or bypassed in order to arm most current systems.

AWG – American Wire Gauge is the common standard for measuring wire diameter. Larger numbers represent smaller diameter wire, and vice versa. A cable is usually described by its AWG size followed by the number of wires (conductors) it contains. For example, a cable listed as 22-4 is a four-conductor cable made up of four wires, each 22 gauge (most system makers specify 22 gauge as the minimum for their systems to be installed to UL standards).

“B” Connector – A small insulated connector used to join and insulate two or more wires at a splice. The stripped ends of the wires are placed inside the connector, and it is crimped with pliers or (preferably) a crimping tool. The connectors are often call “beanies” or “chicklets” by installers.

Backup Battery/Standby Battery – A rechargeable battery, normally in the control enclosure, that provides power to the system in the event that AC power is lost. In some systems, it is also used to supply extra current if needed during an alarm situation (to help power the sirens, for example). It is sometimes referred to as the Backup Battery.

Bell – Industry term for the sounding device, usually a siren, that loudly announces that the system is in alarm. In early alarm systems, the device was usually a large bell mounted on the outside of a building. Although these are rarely used now, the term has persisted.

Bell Cutoff – The amount of time before an alarm system’s siren (or bell) shuts off automatically after an alarm takes place. In many jurisdictions, this is required by law to be between 5 and 10 minutes.

Bypass – To deactivate a zone or zones before arming the system. For example, the user might want to arm the system while leaving the upstairs window(s) open for fresh hair. The window zone would be bypassed at the keypad before arming the system. Some alarm brands use the word “shunt” for the same function.

“Can” – Installer jargon for the enclosure that houses the control unit motherboard and usually the battery.

Central Station/Monitoring Center – An location that monitors alarm systems transmissions and contacts subscribers and/or local authorities if an incident occurs. Most often, an alarm system communicates with the central station by telephone.

Chime – A sound that keypads can be normally be programmed to make when a zone is opened or closed. The opening of a front door, for example, might cause the keypad to chime. This function normally only works when the system is NOT armed.

Communicator/Dialer – The subsystem on an alarm control that automatically dials a central station and relays information about the protected building. It communicates digitally with the central station receiver; most cannot produce spoken words that could be understood by a human, and older models can ONLY communicate with a central station receiver.

Contacts – standard term for the switches that are mounted at doors and windows to inform the control panel of openings and closings. Most are magnetic reed switches, but some older and specialty models are mechanical switches.

Control Panel – An alarm system’s main circuit board, a backup battery, and possibly other components necessary for the control of the system. It is NOT the Keypad, although in some modular systems, the keypad is integrated with the control panel. Normally all of the components are contained in a metal or plastic enclosure “can”.

CS – Central Station

Default – The factory-set value for any programmable option in an alarm system. When you “default the system”: you use either a hardware or software operation that resets all options in the system to values they had when the system left the factory. This should not be done lightly, as installers often activate settings that defeat this procedure.

Disarm – To turn the security system off.

End-of-Line Resistor/EOL – A resistor placed in an alarm zone circuit, ideally at the last device on the loop, allowing the control panel to “supervise” the circuit (make sure that everything in that circuit is intact), and allow functions like mixing normally open and normally closed devices in the same circuit/loop. Many systems provide an option for turning off the requirement for these resistors, but they are usually still required for zones set as fire/smoke loops.

Entry Delay – The time delay before an alarm occurs after a triggering event. Typically, if a door opens while a system is armed, a warning will normally sound for the number of seconds set in programming before the siren sounds and/or the control panel calls the monitoring center.

Exit Delay – The time delay between the point a system is turned on (armed) and the point when it becomes active. During the delay, tripping a detection device (opening a door, moving in front of a motion sensor, etc.) will normally NOT cause an alarm.

Hardwired – A method of installing an alarm system where all of the contacts and other devices are connected to the control panel by wires.

“Heat”/Heat detector - A device that triggers an alarm zone if the temperature in a space rises at an unusually rapid rate or reaches a pre-set heat limit, or both. Heats DO NOT detect smoke, although some smoke detectors have heat sensors built in to their circuitry.

Installer Code -- A (usually) four-digit code that allows access to the alarm system to configure and program various functions. Normally, the installer code cannot arm or disarm a system, and the code only works while the system is disarmed.

Keybus/data bus – The set of connections on an alarm system that allows other digital devices to communicate with it. Keypads and expansion modules are among the devices that would be connected to these same terminals. Most systems use 4 wires, but the number can range from 3 to 6.

Keypad/Touchpad – A remote device that allows a user to control an alarm system by pressing keys numbered 1 through 0. In addition to the keys, almost all keypads have some means of displaying information to the user about the system. The keypad is not the Control Panel, although in some wireless systems, the keypad is mounted directly on the control panel.


Line Seizure – An system feature that allows the alarm dialer to take complete control of the house telephone system in the event of an alarm. This is intended to prevent an intruder from disabling the alarm system phone dialer by simply taking a phone off hook.

Loop – A common term often used for the security zone wiring circuit. Such a zone might have multiple switches forming one continuous loop.

Master Code – The primary user code for a system (usually 4 digits) that allows the primary user of an alarm system to turn the system on (Arm) or off (Disarm) and is usually the code that can add, remove or change secondary user codes.

Memory – Most alarm systems have a function for storing the most recent alarm event and displaying it on command.

NC/Normally Closed – Alarm system wiring in which detection device(s) use a switch or circuit that is closed when the door or window is closed, or active devices like motions are not being triggered (its “normal” condition).

NO/Normally Open - Alarm system wiring in which detection device(s) use a switch or circuit that is open when the door or window is closed, or active devices like motions are not being triggered (its “normal” condition). Fire devices normally use this style of circuit.

Partition – A means of splitting an alarm system into two or more “virtual” alarm systems. For example, one system could serve two offices, with certain zones assigned to one office, certain zones assigned to the other, and some zones (like a common foyer) assigned to both. Each partition would have its own keypad for independent control.

PIR - “Passive InfraRed”, the most common type of motion detector. It is passive because it does not emit any type of energy, but rather senses the relative movement of body heat through the zones “sees” the coverage area in.

Programming – Setting the options that determine the operation and behavior of the alarm system.

Resistor – A small semiconductor that changes the electrical properties of a circuit by changing the electrical resistance. Resistance value is expressed in Ohms. Different alarm systems require different resistor values for various functions.

RJ31X – A special telephone jack that allows a user to disconnect the house telephone system from the alarm panel in case the system malfunctions without disturbing the basic line seizure wiring. Only required if the system is connected to the house telephone wiring.

Security system – Also called an Alarm System, an interconnected system of components which monitors the perimeter and interior of a building.

Smoke/Smoke detector – A sensor that detects smoke in the air, which is connected to an alarm system control panel and relies on the alarm system for power and notifying the occupants (Smoke ALARMS have their own internal sounders, and are usually independent of a control system). Some system smoke detectors also include Heat detectors that trigger an alarm if the temperature in a room rises at an unusually rapid rate or reaches a pre-set heat limit, or both.

“Snake” – (noun) A tool with a long, usually flat, and somewhat flexible wire used for fishing wire through enclosed spaces; it coils inside a case for storage. Some models are made of fiberglass.
Often used as a verb to refer to the process of fishing wire through walls and other void spaces.

Supervision – A configuration that allows an alarm system control panel to make sure that other components of the system are intact.

Voice Dialer – A device that will automatically call pre-programmed telephone numbers, and play a recorded voice message that a human listener can understand, when triggered by the alarm system. It’s usually an add-on device, but a small number of systems have this function built in.

Wireless – Alarm system devices that use radio frequency (RF) transmitters and receivers in place of hardwiring. This can be in place of hardwired zones, or in addition to hardwired zones, depending on the system.

Zip Cord – Cable in which each conductor is insulated, but there is no additional jacket surrounding them and can be easily split lengthwise, like speaker cable, for example. Usually one of the conductors has a different color wire, or a stripe or ridge to be able to differentiate it from the other.

Zone – A specific protected area of a building, as seen by the alarm system. A zone might include a single door, multiple windows, a motion detector, or any other detection device that is monitored by the control panel, alone or in a group. Wireless devices are normally each a zone by definition. This is one of the most custom parts of alarm systems, because the zone behavior is affected by programming. Some systems use phrases like “sensor group” instead of “zone type”.