Alarm Monitoring Glossary

ARC (Alarm Receiving Centre): A continuously staffed control room that receives alarm signals and acts on them under procedures agreed in advance for each property. ARCs handling police-response signals in the UK are certificated to BS EN 50518.
ATS (Alarm Transmission System): The signalling path between an alarm system and an ARC, together with the equipment at each end. Classified by EN 50136 according to how quickly a failure is detected and reported.
Audio challenge: A feature of remotely monitored CCTV where an operator speaks to an intruder through a loudspeaker on site. Frequently ends an intrusion before anything is taken.
Bells-only alarm: An alarm that sounds a siren at the property but sends no signal anywhere. Nobody is notified unless a person nearby hears it and chooses to act. No UK police force responds to a bells-only activation.
BS 5979 withdrawn: The former British standard for alarm receiving centres. Withdrawn and replaced by BS EN 50518. A provider still advertising BS 5979 certification is quoting a withdrawn standard.
BS 7858: The British standard for security screening of personnel, covering identity, employment history and criminal record checks. Applies to people holding keys to your property or working in a monitoring centre.
BS 7984: The British standard for keyholding and response services, covering how keys are held, secured and used, and how attendance is carried out.
BS 8243: The British standard for designing and installing alarm systems so that activations can be confirmed, in order to reduce false alarms. It underpins the confirmed-activation requirement that police response depends on.
BS 8484: The British standard for lone worker services and devices, covering provision, monitoring and police escalation. Compliance is what gives a lone worker service access to an enhanced police response level.
BS EN 50131: The European and British standard series for intruder and hold-up alarm systems, covering system requirements, components and installation. It defines the four security grades used to match a system to the risk at a property.
BS EN 50518: The current standard for monitoring and alarm receiving centres, covering the building, physical security, resilience, staffing and procedures. It replaced BS 5979, which is now withdrawn.
BSIA (British Security Industry Association): The trade association for the UK private security industry. It publishes guidance and represents members, but it is a trade body rather than an inspectorate — membership is not the same as certification.
Confirmed activation: An activation supported by more than one independent indication of a genuine intrusion — typically two separate detectors triggering, or a detector plus audio or video verification. Police forces treat confirmed activations more urgently than unconfirmed ones. System design for confirmation is covered by BS 8243.
Digital Voice: Telephone service delivered over broadband rather than the analogue network. It depends on your router, so it fails when power or internet fails, and older alarm communicators expecting analogue signalling tones may not work over it at all.
Dual-path signalling: A configuration where the alarm can reach the ARC by two independent routes, typically broadband and a mobile network, so failure or sabotage of one does not leave the property unmonitored. Standard on commercial premises and often an insurer requirement.
EN 50136: The standard for alarm transmission systems, classifying signalling paths by transmission time, how quickly a fault is detected, and the resilience required. Higher categories imply shorter detection times and more redundancy.
Engineer code: The code allowing access to an alarm system's programming, held by the maintaining company. Not knowing it is a common obstacle when taking over a system in a newly occupied property, and sometimes forces a panel replacement.
Entry and exit time: The permitted period to leave after setting, or to reach the keypad and unset after entering, before the system treats the activity as an intrusion. Set too long it weakens the system; set too short it generates false alarms.
Environmental monitoring: Monitoring for non-security conditions such as water leaks, low temperature or power failure, using the same signalling path as an intruder alarm. Often more valuable than intruder cover on empty properties, where burst pipes cause more loss than burglary.
False alarm: An activation with no genuine cause, usually from user error, pets, insects, poorly sited detectors or ageing sensors. Forces operate a false-alarm allowance over a rolling twelve-month period; exceeding it can suspend or withdraw a URN, with thresholds set locally rather than nationally.
Hold-up alarm: A manually operated alarm used to summon help when under threat, as distinct from an automatic intrusion detector. Covered alongside intruder alarms in BS EN 50131 and treated differently from an intrusion signal by an ARC.
Keyholding: A service in which a security company holds keys to a property and attends when the alarm activates, checking the building and either resetting the system or escalating. Covered by BS 7984, with staff screened to BS 7858.
Lone worker alarm: A personal device allowing an employee working alone to raise an alert to a monitoring centre, which can listen, locate and escalate. Where provided and monitored to BS 8484, it can access an enhanced police response route.
Maintenance contract: The ongoing agreement under which an approved company services an alarm system. Distinct from the monitoring contract, and required as a condition of holding a police URN — if it lapses, police response can be withdrawn.
NPCC (National Police Chiefs' Council): The body that sets national policy for policing in England and Wales, including policy on police response to security systems and the conditions attached to URNs. It succeeded ACPO, whose name still appears in older alarm industry material.
NSI (National Security Inspectorate): A UK inspectorate body that audits security and fire companies against the relevant standards and publishes a register of those approved. One of the two routes — the other being SSAIB — by which a company qualifies to obtain police response for its customers. NSI Gold adds an audited quality management system.
Open and close reporting: A commercial monitoring feature where the ARC is told when premises are set and unset, and raises an exception if it does not happen within an expected window. Catches both a forgotten lock-up and a member of staff being prevented from setting the alarm.
PSTN (Public Switched Telephone Network): The traditional analogue telephone network, now being retired across the UK in favour of digital voice over broadband. It carried its own power and stayed up during a mains failure, which is why alarms that signalled over it need migrating to broadband or mobile paths.
Redcare withdrawn: BT's alarm signalling service, for decades the UK default, closed in 2025 following an announcement in 2023. Systems that used it required migration to an alternative signalling provider such as CSL, WebWayOne or Chiron.
Secured by Design: A police-backed UK crime prevention initiative that accredits products and building designs meeting its security requirements. Relevant when specifying physical security around an alarm, and often referenced by insurers.
Security grade: A classification under BS EN 50131 describing the capability of intruder a system is designed to resist, from Grade 1 (low risk, unskilled intruder) to Grade 4 (high risk, planned attack with specialist equipment). Most UK homes are specified at Grade 2, most commercial premises at Grade 2 or 3.
Signalling device: The hardware that connects an alarm panel to an ARC and transmits activations to it. Separate from the control panel, and usually the only component that needs adding to make an existing alarm monitorable.
SSAIB: A UK certification body for security, fire and telecare providers, and the main alternative to the NSI. Equally accepted by police forces for URN purposes, and it publishes its own register.
Standby battery: The battery that keeps an alarm panel running during a mains failure. Minimum duration is a graded requirement under BS EN 50131 rather than a manufacturer choice, and it is finite — a multi-day outage will outlast it.
Supervision: Regular automatic checking of a signalling path, so that a loss of connection is itself detected and reported as an event within a defined time. Supervision is why a properly monitored system notices a cut line rather than simply going quiet.
Takeover: The process by which an approved company inspects an alarm installed by someone else, then maintains and monitors it — either as found or after specified remedial work. Normally far cheaper than replacing a working system.
Tamper: Detection of interference with alarm equipment or wiring — opening a detector housing, cutting a cable — reported separately from an intrusion. Tamper requirements get stricter at higher system grades.
Telecare: Monitored personal alarm services for vulnerable or elderly people, typically a pendant or wristband raising a call to a monitoring centre. A separate certification scope from intruder alarms, though often provided by the same centres.
Unconfirmed activation: An activation from a single detector, with nothing corroborating it. The great majority are false, and they do not normally attract a police attendance even at a property holding a valid URN.
URN (Unique Reference Number): The reference a police force issues to a specific monitored alarm system at a specific address, which allows an ARC to pass activations from that system to the police. It belongs to the address and the force, is applied for by an approved company rather than by the owner, and can be suspended or withdrawn for excessive false alarms.
Video verification: Use of camera footage by an ARC operator to establish whether an activation is genuine. Can support a confirmed activation, which is one reason commercial sites pair CCTV monitoring with intruder monitoring.
Zone: An individually identified part of an alarm system, usually one detector or a small group, so that the ARC can see which area of a property activated rather than just that something did.