Fire Alarm and Security Industry Terminology:

"Yes, but what does it all mean?"
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in Young Frankenstein

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Refers to the method of signal transmission utilized by an ALARM SYSTEM to communicate an emergency signal to a CENTRAL STATION. The category itself is no longer being used but in order for an installation to have received a "AA Listing", the equipment and installation methods also had to meet a very strict standard.

When measuring sound pressure levels, this scale on the meter most closely resembles the response of the human ear.

Is a space (or area) within a building that can be distinguished from other spaces (or areas) either acoustically, environmentally or by the usage (type of occupancy), and is used in designing a speaker layout that considers factors such as reverberation time, sound reflective materials (used in the area) and ambient sound pressure levels.  An ADS allows the building designer to divide a building into areas (or spaces) and identify those areas that require a higher level of speech intelligibility.

Refers to a method of signal transmission to a qualified central monitoring station in which communication between the premises fire alarm communicator and the station receiver is continuously supervised. Loss of communication will result in a trouble condition at both the communicator and the receiver and will trigger a predetermined response by personnel at the monitoring centre. See also our sample TIP and DIRECT LINE.

Any of a family of addressable fire alarm components and modules that include heat detectors, smoke detectors, manual stations, monitor modules, relay modules, etc.  These devices incorporate circuitry that enable them to communicate bi-directionally with the common control or transponder.


Air Handling Unit.

Consists of a CONTROL PANEL, INPUT DEVICES, OUTPUT DEVICES, and their associated WIRING to comprise a means of notifying the occupants of a building (or communicating to a CENTRAL STATION) of an INTRUSION, FIRE, FLOOD, SUPERVISORY SIGNAL, etc.

A method by which an alarm (or supervisory) event must undergo another process in order to confirm an actual condition exists which requires the activation of an OUTPUT DEVICE. This may include the requirement for another independent device monitoring the same protected area to enter an ALARM state. It may also involve PROGRAMMING SOFTWARE (or FIRMWARE) that requires one event trigger to follow another within a specified (and usually programmable) time frame.

Canadian Standards define this as a component that “has a life safety application, and that is connected to the a fire alarm system, but is not part of the fire alarm system”.  To further clarify, an ancillary device can provide either an input function (i.,e. damper position indicator, exhaust fan “on” indication), or an output function (i.e. door holders, magnetic door release, elevator homing, pressurization fan activation), but cannot ACTIVATE the fire alarm system.

A device which displays ALARM, SUPERVISORY, and TROUBLE conditions and that is most often used when the main fire or burglary control unit is mounted in a location not easily accessible. Modern ANNUNCIATORS have the ability to mimic the control functions of the main panel.

An individual (or organization) that has demonstrated the required technical ability and knowledge to perform maintenance, inspection, and repair on specific equipment or systems to the satisfaction of the local authority. Manufacturer specific training may be included in the requirements to achieve "approval". A good example of approval criteria can be found on the City of Vancouver's List of Approved Fire Alarm Verification Agencies.

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An individual or organization that adopts and enforces the codes, rules, and by-laws which govern the various concerns of a community. Commonly referred to as the "final authority" for any matters relating to LIFE SAFETY and BUILDING CONSTRUCTION within that specific community.

A rechargeable source of standby power for the ALARM SYSTEM in the event of a power failure. The BATTERY is sized to take into consideration the number of INPUT DEVICES associated with the ALARM SYSTEM, the time required by CODE to operate in STANDBY and ALARM, and a safety factor (often referred to as a DE-RATING FACTOR).



When an INPUT DEVICE (such as a motion sensor) is electronically neutralized so that a FAULT on that sensor does not trigger an OUTPUT DEVICE. In the case of a MOTION SENSOR, this allows the occupants to freely move about while the BURGLAR ALARM SYSTEM is ARMED. In the case of a FIRE ALARM SYSTEM, a TROUBLE indication should register when an INPUT DEVICE is BYPASSED.

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Short for CANADIAN SECURITY ASSOCIATION. This is an association of alarm companies in Canada that advocates for the industry in matters concerning local law enforcement response, certification, standards, etc. For more information, click here.

An OUTPUT DEVICE triggered by the ALARM SYSTEM when its ARMED or it detects the sudden loss of the protected premises telephone line. It signals either of these events to the CENTRAL STATION so that an appropriate response can be instituted.

A facility that provides monitoring services for signals generated by their customer's ALARM SYSTEMS. Some CENTRAL STATIONS are listed by independent testing or certification facilities like UL, ULC, FM, NACOSS.

A communications format developed by Ademco® (Division of Honeywell) that utilizes bursts of DTMF tones in order to transmit alarm events over a standard telephone line (POTS) or cellular network.  Also called Contact ID.

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Common Intelligibility Scale - a measure of a sound system’s intelligibility.

CLASS "A" CIRCUIT (Type "6" or Style "Z" Loop):
A type of alarm circuit which has four physical terminations in a common control's input, output, or DCL (SLC) circuits and which employs a single continuous two-wire loop (path) from the panel to the first device, on through to the last device, returning to the panel via a separate entry point in the enclosure.  A break (or "open") in the wire along any part of the loop will result in a "trouble" condition at the panel but will not otherwise affect the operation of any device connected in the loop.  This type of circuit is commonly employed in an addressable communications circuit (also termed SLC or DATA COMMUNICATION LINK) RISER from which analogue devices on each floor of a multiple story OCCUPANCY are quite often "T" TAPPED through individual ISOLATION MODULES.  A wire short imposed on a CLASS "A" SLC (or DCL) circuit will result in failure of both segments of the circuit.  A similar condition on a conventional INITIATING CIRCUIT will result in an alarm condition that a RESET of the common control will not clear while a TROUBLE indication will be displayed if an OUTPUT CIRCUIT is shorted.

CLASS "B" CIRCUIT (Type "4" or Style "Y" Loop):
A two-wire input or output circuit which terminates in an END-OF-LINE DEVICE which provides circuit SUPERVISION. (An END-OF-LINE DEVICE is normally not required on a DATA COMMUNICATION LINK or SLC circuit.)

A fire in ordinary combustibles such as wood, paper, cloth, trash and plastics.

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A fire in flammable liquids such as gasoline, petroleum oil and paint. Class B fires also include flammable gases such as propane and butane. Class B fires do not include fires involving cooking oils and grease.

A fire involving energized electrical equipment such as motors, transformers and appliances. Remove the power and the CLASS "C" fire becomes one of the other classes of fire.

A fire involving burning metals and their chemical oxides. Magnesium, phosphorus, sodium and powdered aluminium (the latter is used in solid fuel rockets) are the more common examples. Class D fires utilize chemically generated oxidants and as such are extremely difficult to extinguish. In many cases the only method is "no method" (in other words you must allow it to burn itself out) and the role of the Fire Fighter is primarily concerned with stopping the possible spread of the fire to adjacent vehicles or structures.

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Involve cooking oils, grease and fats.

A device or assembly for closing an opening through a fire separation (such as a door), and includes all components such as hardware, closing devices, frames and anchors.

Any liquid having a flash point at or above 37.8 deg. C and below 93.3 deg. C.

Is the means by which INPUT DEVICES communicate a fault to the building occupants (or a CENTRAL STATION) through the activation of a programmed response that may or may not include specific OUTPUT DEVICES.  The CONTROL PANEL usually consists of a circuit board (also referred to as the MOTHERBOARD or COMMON CONTROL), and is usually housed in a metal box sized to accommodate both it and a standby source of power (the BATTERY). INPUT DEVICES, ZONE EXPANDERS, KEYPADS, and OUTPUT DEVICES are connected to the main circuit board.

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The means employed by an ADDRESSABLE type control panel to communicate with compatible devices in the field.  These may include INPUT DEVICES, OUTPUT DEVICES, ANNUNCIATORS, and remote TRANSPONDERS.

A cover (usually metallic) designed to shield sensitive components and terminations within a common control enclosure so as to prevent inadvertent or accidental contact with potentially dangerous voltages by an end-user or operator.  The cover is removable, usually by qualified service personnel who are familiar with the equipment’s field connections, for service and troubleshooting purposes.

(As defined in CAN/ULC-S537-13 - Standard for Verification of Fire Alarm Systems) “For the purposes of this Standard, this term refers to a device or function that does not operate as intended.”  A deficiency can also refer to an improperly installed fire extinguisher (wrong type, wrong size, or wrong height above the floor (or not mounted on the wall at all).  Consultation with the Authority Having Jurisdiction is recommended because the term has been applied to a variety of different deviations and inconsistent practices.

A circuit triggered by an INPUT DEVICE that allows the building occupants a set period of time in which to DISARM the ALARM SYSTEM.  The time period is adjustable through system PROGRAMMING and usually takes into account how far the KEYPAD is from the main entry door.  It is desirable to have the ENTRY DELAY set as low as possible.

A term that usually refers to a multiplier used in the calculation of a BATTERY's standby capacity and which actually serves to determine the correct size of BATTERY to use in a fire alarm system or other mission critical applications.  The Building Code will usually specify the amount of stand-by and alarm time required based on the type of occupancy.  The number takes several factors into account which may affect the battery's capability to produce the required power over it's service life.  These include age, cell degradation, charger condition, environmental factors, purity of the internal components, construction, etc. The most commonly used DE-RATING FACTOR is 1.3 (some would argue 1.2 or 1.25). A sample calculation (*based on a 30 minute alarm time requirement) is:

.350 amp
(supervisory current)
24 hours
(required standby time)


1.8 amps
(alarm current)
0.5 hours
(alarm time)


(de-rating factor)


12.09 AH


In the above calculation, the minimum battery size to meet the requirements of CODE would be 13 AH (Amp Hours).  You should round up to the next highest whole number.  It would be suggested  that the nearest size equivalent (available from most wholesalers) is 18 AH.  Keep in mind that (in this example), either 12AH or 18AH would work if the manufacturer's actual de-rating factor (as suggested in the installation manual for the panel) was 1.2.  This highlights the necessity of having access to the panel’s manual for even the ANNUAL system test!

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This is an OUTPUT DEVICE utilized by the ALARM SYSTEM to communicate an emergency signal to a CENTRAL STATION or a pocket pager.  It uses the premises normal telephone line to transmit the signal and is the most cost effective means of doing so.  Some DIGITAL COMMUNICATORS employ TLM (TELEPHONE LINE MONITORING) to supervise for the sudden absence of the subscribers phone line which results in the activation of additional OUTPUT DEVICES to warn the building occupants or the CENTRAL STATION.  You can read more about communicators in our TIPS  section.

Also known as Dedicated Line and Direct Wire.  This is a specially installed telephone line that links the premises ALARM SYSTEM directly to a CENTRAL MONITORING FACILITY or CENTRAL STATION.  The line is supervised to prevent tampering.  Any interruption is immediately signaled to the CENTRAL STATION and appropriate action is taken depending on the level of response required.  In addition to certain types of FIRE ALARM SYSTEMS, banks, financial institutions, ATM machines, some jewelery and gun shops require this level of security.  You can read more about communicators in our TIPS section.

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The act of turning off or deactivating a BURGLAR ALARM or SECURITY SYSTEM.

Most modern alarm panels (both burglary and fire) are equipped with the ability to be programmed by a remote computer (or local laptop).  The applicable software to perform this function is furnished by the system's manufacturer.  This allows the MANUFACTURER TRAINED TECHNICIAN (or service company) to make changes to the panel's software and firmware which ultimately affects the operation of the system.  It also helps to speed the set-up of the system and often incorporates "error checking".  In the case of a fire alarm system, changes to programming (or the updating of firmware) will usually trigger the requirement for a VERIFICATION INSPECTION.

Refers to a number of INPUT DEVICES that employ two separate methods of detecting an alarm or fault condition (short for DUAL TECHNOLOGY) and thereby eliminating or severely reducing the chances of a FALSE ALARM in environments where single technology sensors may not be appropriate for use. DUAL TECHNOLOGY fire sensors typically incorporate both a smoke and heat detection components, activation of either of which will result in an ALARM condition.

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Short for DIGITAL VOICE ACCESS CONTROL SYSTEMS.  A means by which a number of ALARM SYSTEMS can communicate with a CENTRAL STATION over a network type of connection. Similar to DIRECT WIRE.  It utilizes transponders connected to the CONTROL PANEL that are continuously interrogated by special receivers in the CENTRAL STATION.  Many such receivers can also perform "on premises" functions like arming, disarming, zone bypassing, etc.  You can read more about communicators in our TIPS section.

When a RESISTOR, it is normally "paired" to an alarm panel's input or output circuit and has a specific value determined by the equipment manufacturer.  A POWER SUPERVISION RELAY is often used to monitor a panel's auxiliary power output when it is used in conjunction with four wire SMOKE DETECTORS, BEAM DETECTORS, or other DEVICES which may draw power from a panels auxiliary outputs.  Both these types of End-Of-Line Devices are normally installed as the last device in a CLASS "B" type circuit.

That part of a means of egress that leads from the floor area it serves, including any doorway leading directly from a floor area, to an open public thoroughfare or to an exterior open space protected from fire exposure from the building and having access to an open public thoroughfare.

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When the ALARM SYSTEM is triggered without an obvious cause (intruder, fire, etc.).  Equipment malfunction (due to environmental factors or outright failure), vandalism, and user error are the common causes of FALSE ALARMS.

A device intended for use in horizontal assemblies required to have a fire-resistance rating and incorporating protective ceiling membranes, which operates to close off a duct opening through the membrane in the event of a fire.

A device designed to deliver a calculated volume of water at a specific pressure for a sprinkler or STANDPIPE system. It is usually found in HIGH RISE residential or commercial buildings. It is usually electrically driven, but in some instances may also be engine driven and is normally activated when a drop in water pressure is sensed (such as would be caused by the activation of a SPRINKLER HEAD). It is extremely important to test run a fire pump on a regular (monthly) basis to prevent the build-up of corrosive elements which may impinge upon or hinder the flow of water from a sprinkler head.

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A document which outlines the responsibilities of the building's occupants in the event of a fire. It assigns the FIRE SAFETY OFFICER, DEPUTY FIRE SAFETY OFFICER, and FLOOR WARDENS and details the requirements for periodic testing of the building's life safety systems (including the elevator, generator, fire pump, emergency lighting, hoses, extinguishers, and sprinkler system). It also contains a list of those occupants which require special assistance, and provides detailed plans of each floor area for reference purposes by responding fire fighting personnel.

Any liquid having a flash point below 22.8 deg. C and having a vapour pressure not exceeding 275.8 kPa (absolute) at 37.8 deg. C.

The minimum temperature at which a liquid within a container gives off vapour in sufficient concentration to form an ignitable mixture with the air near the surface of the liquid.

An enclosed passageway for conveying flue gases (usually formed by combustion).

Factory Mutual. This is a US based certification agency. For more information, visit the Factory Mutual website.

This is an INPUT DEVICE which is triggered by either the sound of breaking glass or the sudden impact of something against a pane of glass. WINDOW BUGS, FOIL, AUDIO GLASS BREAK SENSORS all fall into this "family" of INPUT DEVICES.

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A term often used to describe an existing functional fire alarm system that does NOT meet the installation or design requirements of modern Codes and Standards, but is still viewed as an acceptable means of notifying occupants to an emergency.  Grandfathered systems may require additional procedures and response stratagems in order to successfully achieve compliance within the framework established by the local AUTHORITY HAVING JURISDICTION.  This is often achieved through a consultative process with the building owner and may entail a review by a Code Consultant or other expert building safety professionals.

A condition in which an alarm system references a structure's common electrical ground plane. This can be caused by a wire to an INPUT or OUTPUT DEVICE that is "pinched" or been abraded so as to contact the metal back box (or conduit). In the latter instance, the wire can become abraded (or skinned) during the installation process exposing the bared conductor(s). In some systems a fault condition can be artificially generated when the wiring is incorrectly terminated or when multiple power supplies are involved. Another common cause is water ingress at a field device such as a ceiling mounted smoke or heat detector. Ground faults are not difficult to pinpoint but often present a challenge to the servicing technician when more than one are present on a system or if the fault is intermittent (as may be the case for water ingress). For information on how to solve a ground fault trouble, you might want to visit our TIPS page.

NOTE: It is extremely important that a building FIRE ALARM SYSTEM is able to detect a GROUND FAULT. If for some reason, ground fault detection has been inhibited or otherwise compromised, the FAS may not function correctly or start causing FALSE ALARMS.

This is an INPUT DEVICE specifically designed to detect a rapid rise of temperature in a protected area. It is also triggered when a specific temperature is reached. HEAT DETECTORS come in three main fixed temperature settings: 135, 180 and 200 degrees Fahrenheit. HEAT DETECTORS are also known as fire detectors. As they are activated by heat, they are not considered a LIFE SAFETY device.

A specially designed heating element comprised of a coated wire which is wrapped around exposed domestic or WET SPRINKLER SYSTEM piping and is thermostatically controlled to prevent the water in the pipe from freezing. HEAT TRACED piping is usually insulated with glass fibre. In parkades or other exposed locations, tears or other damage to the insulation material (or covering) should be investigated and repaired. Loss of power to the HEAT TRACE CONTROLLER should result in a supervisory trouble signal on the FIRE ALARM SYSTEM and often only requires a RESET of the system once power is restored.

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HOLD-UP BUTTON (also known as a PANIC BUTTON):
This is an INPUT DEVICE that is manually activated by an occupant in a protected premise to signal an emergency to the CENTRAL STATION.

Describes the field wiring and terminations in the FIRE ALARM or SECURITY SYSTEM's common control to which the building's signalling or notification appliances are connected.

Any of a family of devices designed to detect unauthorized access, fire, smoke, flood, motion or any condition requiring notification or response by a building's occupants or a CENTRAL STATION. INPUT DEVICES can be MAGNETIC DOOR CONTACTS, GLASS BREAKAGE DETECTORS, MOTION SENSORS, PHOTOELECTRIC BEAMS, SMOKE DETECTORS, WATER DETECTORS, LOW TEMPERATURE DETECTORS, etc.

Is the means of measuring of the clarity of verbal announcements over a public address system.  Two measurement scales have been established: CIS (Common Intelligibility Scale) and STI (Speech Transmission Index).

Any of a family of field devices designed to ensure survivability of the fire alarm system if one segment thereof becomes compromised by an open circuit or short circuit condition.  There are three types of isolators which may be deployed: 
Data Communication Loop (DCL) Isolators (sometimes referred to as SLC Isolators) ensure communications with active field devices such as heat, and smoke detectors, manual initiating stations, and signalling modules remains unaffected (or is minimized) by a circuit trouble condition.  While it is recommended that DCL isolators be located in an electrical service room, they can also be deployed in the field;
Signal Circuit Isolators are normally installed to serve suites in a residential occupancy.  One such isolator will handle two suites.  If the in-suite signalling appliance (usually a buzzer) is compromised for any reason, the signalling devices in the other suites serving the floor will remain unaffected.  A “trouble” condition will be displayed on the common control however;
Power Buss Isolators are designed to protect the integrity of a power distribution riser usually employed by a distributed (addressable) system (some conventionally wired systems may also employ these units).
We review the testing procedures of these three types of isolators in this FAQ.

A device that controls the functions of an ALARM SYSTEM, can access both user and installer programming levels, and can act as both an INPUT DEVICE and an OUTPUT DEVICE. The entry of a numeric code sequence will determine the response of the ALARM SYSTEM. It usually consists of a numeric keypad modelled after the standard telephone touch pad.

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Usually refers to an additional service provided by an ALARM COMPANY whereby keys are provided to the protected premise to allow access by security personnel in the event of an alarm event.

A term often used to describe replacing (or changing out) a detector (or field device) with the same type of detector (or field device) (e.g. an old smoke detector for a new smoke detector, or a heat detector for another heat detector).  “Like-for-like” implies that the detector will have the same ratings and employ the same technologies, but when it comes to smoke detectors, you should consider the nature and type of combustibles in the area served by the device before replacing it “like-for-like” (an exception would be addressable type smoke detectors as the fire alarm control will only recognize the exact type).

This is an ALARM SYSTEM that is not connected to a CENTRAL STATION, but is designed to activate a local OUTPUT DEVICE like a siren or bell.

A condition in a DRY PIPE SPRINKLER SYSTEM in which the air pressure has fallen below a pre-set level. This is utilized to warn the building's occupants that the system's air compressor may be compromised (or the power to the unit may be turned off) and a further reduction in pressure may cause the system to TRIP.

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This is an INPUT DEVICE that is normally used to detect the opening of a protected door or window. On sliding doors or windows, another contact can be installed that will allow an opening for fresh air circulation that is too small for an intruder to fit through (usually four to six inches).

A wall mounted device that is normally located close to an EXIT DOOR that, when activated, will cause the FIRE ALARM SYSTEM to sound in the premises.

A continuous path of travel provided by a doorway, hallway, corridor, exterior passageway, balcony, lobby, stair, ramp, or other egress facility or combination thereof, for the escape of persons from any point in a building, room, or contained open space to a public thoroughfare or other acceptable open space (means of egress includes exits and access to exits).

An ALARM SYSTEM that has been programmed to transmit signals to a CENTRAL STATION or other SECURITY or FIRE CONTROL CENTRE.

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This refers to a family of INPUT DEVICES designed to detect movement within a specific field of view or detection pattern. Most MOTION SENSORS use one of two detection technologies: passive infrared, or microwave. Some sensors have been specifically designed to allow movement of pets (small animals) without triggering an alarm. These are commonly referred to as PET RESISTANT or PET IMMUNE. There are still some older motion detectors in service that use ultrasonic technology to sense movement within their range, but their use has been largely discontinued. A special motion sensor is often installed above an exit door to trigger an electronic release and open the exit door on the approach of an OCCUPANT.

Refers to a method of transmitting fire alarm information from a premises directly to a responding authority's dedicated receiving centre (usually located in the main fire hall). Some municipalities retain the infrastructure to provide this service at a very low monthly cost. See also DIRECT LINE. Can also be a part of a Municipal Call Box system. A special module is installed into a fire alarm panel that is supervised by the receiving equipment for "line fault", "common trouble", "supervisory" and "alarm".

Short for "Notification Appliance Circuit". Also called the Bell Circuit, Signal Circuit, or Output Circuit. OUTPUT DEVICES are terminated to the NAC in either a Class "A" or Class "B" configuration.

Are specific signals transmitted by an ALARM SYSTEM that indicate whether it has been ARMED or DISARMED. Some CONTROL PANELS are capable of storing multiple user codes (normally input through the KEYPAD). Utilizing this feature, a CENTRAL STATION can usually determine who ARMED or DISARMED the system.

This refers to a family of devices used to alert building occupants or an outside agency of a fault, alarm, or trouble condition. These can include BELLS, SIRENS, KEYPADS, COMMUNICATORS, STROBE LIGHTS, BUZZERS, RELAYS and PAGERS.

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This is an INPUT DEVICE that comprises an emitter and a receiver both of which must be in sight of one another. In security type applications, the detector uses a narrow focused beam of infrared light that when broken will result in a fault or alarm. BEAM FIRE DETECTORS operate on a similar principal. The sensor is designed to respond to specific inputs that allow it to discern the difference between SMOKE and HEAT within the protected environment. A complete or partial blockage of the beam in this type of application will result in a TROUBLE condition however, not an alarm.

See MOTION SENSORS. Short for Passive Infrared Detector.

Short for PERIODIC MAINTENANCE AGREEMENT. This is a contract between the building owner (or property manager) and (normally) a fire equipment service company to perform semi-annual and annual testing and maintenance of the life safety equipment on a site.

Short for PLAIN OLD TELEPHONE SERVICE. In British Columbia this is provided by primarily by TELUS. It's essentially the service that's been a staple throughout North America for the last ninety-plus years. Services are routed to the building through overhead lines (or underground) to a central location where it's distributed to the various telephone devices. These days a lot of the old "copper" wires have been replaced with much more efficient fibre-optic cable. This allows for faster transmission and much more data "throughput".

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Is the action of restoring a fire alarm or security system to a "normal" condition (usually following an ALARM or SUPERVISORY TROUBLE).

Short for Security Industry Association.  Also refers to a communications protocol used by alarm panels to transmit events over a standard POTS line.

The means employed by an ADDRESSABLE type control panel to communicate with compatible devices in the field. These may include INPUT DEVICES, OUTPUT DEVICES, ANNUNCIATORS, and remote TRANSPONDERS.

This is an OUTPUT DEVICE installed at the protected premises to audibly signal an alarm to the building's occupants.

A combined smoke detector and audible alarm device designed to sound an alarm within the room or suite in which it is located upon the detection of smoke within that room or suite. There are two different types of sensing technologies utilized: photoelectric and ionization (with photoelectric being preferable in most residential settings).

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This is an INPUT DEVICE used as part of a FIRE ALARM or SECURITY SYSTEM to sense the presence of smoke and products of combustion. There are two different types of sensing technology utilized: photoelectric and ionization (with photoelectric being preferable).

An arrangement of dedicated piping, valves, hoses and associated equipment installed in a building with the hose connections located in such a manner so as to facilitate controlling (or extinguishing) a fire. Only individuals trained in its use should operate this type of equipment.

Speech Transmission Index - a measure of a sound system’s intelligibility.

An OUTPUT DEVICE that employs an intense pulse of visible light to alert the building's occupants to an alarm, trouble or fault condition.

Refers to a level of operational functionality between control units, control units and transponders, and transponders which employ a Class “A” circuit wiring scheme in a single fire alarm zone (applies to Canadian fire alarm installations).

Refers to a level of operational functionality between control units, control units and transponders, and transponders which employ a Class “B” circuit wiring scheme (applies to Canadian fire alarm installations).

Refers to an improved level of operational functionality when a short circuit condition is imposed on the communication loop between control units, control units and transponders, and transponders which employ a Class “A” circuit wiring scheme where the wiring loop passes through a number of fire alarm zones (applies to Canadian fire alarm installations).

A term which refers to an alarm circuit that when cut or tampered with will initiate a fault or trouble signal to alert the building occupants.

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Refers to a condition in which a device supervised by a fire alarm system is moved from it's "normal" state such as would be the case when you close a "normally open" sprinkler valve, or the air pressure in a sprinkler dry system falls below a pre-set level, or the power is interrupted to a sprinkler heat trace controller (these are only three examples of supervisory type signals). In many jurisdictions supervisory signals must be "latching" (that is where a return to the "normal" condition for the supervised device must be followed by a systemwide RESET). A supervisory fault (or signal) is different from a COMMON TROUBLE.

In the security alarm industry, this is a fault on a communicator zone usually attributed to a malfunctioning field device or relay that ultimately causes a large number of the same signals to be transmitted to the central monitoring station. Also called a nuisance alarm.

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Is a programmable feature of most modern alarm communicators enabled by an installer to limit the number of events transmitted on a specific zone or circuit during either a twenty-four hour period or an ARMED cycle. Normally this is utilized to prevent repeated false signals being sent to the central station from a defective field device or common service issues like a loose door contact or an intermittent connection in a sensor. The more common setting is three "events" in a twenty-four hour period. Multiple alarm trips from a device (or zone) is called a "swinger" and when you get dozens of events in a short period the station may also refer to the account as a "runaway". Fire alarm communicators cannot employ SWINGER SHUTDOWN and technicians performing annual testing of monitored fire alarm systems should be confirming this. You can read more about the procedure in our TIPS section.


A trouble condition or trouble light on a fire alarm or security system indicates a condition that might adversely affect the proper operation (or actually compromises part) of the system. The loss of primary power, back-up power, or a wiring problem (such as a cut or an abrasion which might ground a circuit in a back box) are all common "trouble" indications. "Trouble" conditions usually self-restore (that is the system returns to a "normal" state once the trouble has been cleared). A trouble on an input zone may prevent detectors in the circuit from functioning. It is extremely important that system TROUBLES be corrected as soon as possible.  Several of these that you’ll see typically displayed are explained on a separate page called Common Trouble Signals.

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Underwriters Laboratories. An independent certification agency. The Canadian agency has close links to it's US counterpart, but maintains separate standards.

An inspection through which a newly installed or upgraded fire alarm system is tested to CAN/ULC-S537 (the Standard for Verification of Fire Alarm Systems). All affected components of the FAS are electrically tested for supervision, ground fault, and operation. They are visually inspected for correct placement and installation in accordance with the design, applicable Building Code, and the Standard for Installation of Fire Alarm Systems (CAN/ULC-S524). You can see what's involved in a VERIFICATION by downloading a sample Appendix “C” here.

Short for Voice Over Internet Protocol. It is a method of telephone communication which utilizes a cable or DSL modem to facilitate voice communication over a high speed internet connection. More information can be viewed on our Communicator TIPS page.

An input zone which features a programmable delay used in preventing false alarms due to inadvertent activation of flow switches often caused by intermittent and sudden changes in water pressure (sometimes referred to as a “water hammer”).  Some jurisdictions in the United States allow the use of this feature, while others do not.  It’s best to consult with your local authority before you engage this option.  In Canada, employing a programmed delay on an input circuit is not permitted.

This is an ALARM SYSTEM that uses INPUT DEVICES that utilize radio energy on a special frequency to transmit fault, alarm and trouble conditions to the CONTROL PANEL.

An INPUT circuit that when faulted will trigger a programmed response in the CONTROL PANEL. ZONES typically denote areas of the building (or premises) and may also identify specific device types (pull stations, smoke detectors, heat detectors, etc.). These days, ADDRESSABLE PANELS utilize software zones (ones actually programmed to illuminate a specific indicator lamp) as opposed to the older style conventional panels in which the zones are "hardwired".

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