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Intruder Alarms - Next Generation Networks & Next Generation Access [Hardfacts]


The telecommunications industry is increasingly embracing new digital data transmission concepts, namely "Next Generation Networks" (NGN) and "Next Generation Access" (NGA).

  • NGN refers to the use of digital Internet Protocol (IP) technology in place of analogue switched circuit (PSTN) technology within telephone networks/exchange equipment.
  • NGA refers to new ways of connecting customers to the NGN, i.e. by means of optic fibre cables from exchanges to roadside cabinets, called Fibre To The Cabinet (FTTC); or directly into customer's premises, called Fibre to The Premises (FTTP).

The use of NGN/NGA reflects the latest telecommunications technology, and is necessary to improve data transmission capacity/access speed to satisfy increasing/expected demand.

Although much is said about its advantages, NGN/NGA could adversely affect many intrusion and hold-up alarm systems using Alarm Transmission Systems (ATS) to signal alarm events to an Alarm Receiving Centre (ARC); those most likely to be affected being older systems that use a digital communicator* (Digicom) signalling device, of which there are many thousands still in use. NGN/NGA may also affect some fire alarm systems that also use a Digicom, although these a few in number.
Note* Digicoms are so named because they send alarm information messages via a recognised code in the form of digits, e.g. 1, 2, 6 etc, not because they use digital technology.

Background to NGN/NGA

As the UK’s largest telecommunications provider, British Telecom (BT) Wholesale are instrumental in these changes. At present BT manages a huge estate of telephone exchanges and networks operating on different technologies, e.g. PSTN, ISDN and IP (Broadband). This is costly to maintain and leads to inefficiencies. As part of a plan to improve matters, BT is gradually replacing existing exchange equipment and networks with a single new NGN system running on IP, although at present their focus is on the roll out of NGA.

BT’s NGN (21st Century Network - 21CN) and NGA (Infinity) programmes will affect both their direct customers and customers of other Telecommunication providers (Telco’s) who rent services (network links &/or lines from phone exchanges to customer’s premises) from them.

Note. Most Telco’s, e.g. companies like Talk Talk, Virgin Media, etc, being fairly new organisations, commenced their operations using the new NGN &/or NGA technology. As such, if you decide to swap your telephony services to them it is prudent to check that their service is compatible with any ATS used by your current intruder/fire alarm system to connect you to an ARC. Indeed, some Telco’s terms and conditions actually advise users not to connect alarm systems to their networks.

NGN and  21CN
21 CN was the name BT originally gave to their intended programme of phased exchange upgrades (Migration) to NGN. As part of this programme a trial upgrade of around 75,000 analogue ‘phone lines took place in parts of the Cardiff area in 2009, and was extended in 2010 to include all Cardiff area lines.

Although deemed a success, BT’s priorities then changed and, rather than a phased roll out across the whole UK, they announced that further exchange upgrades would only take place as a need arose. This would either be because of exchange capacity limits being reached, or because of the need to replace life expired exchange equipment.

Will a NGN upgrade be announced?
Originally, BT intended to write to all affected users some time in advance of any scheduled 21CN upgrade. However, as such work will now take place on a piecemeal basis, and then maybe at very short notice in response to equipment breakdown, customers may have little or no time to prepare, and indeed may only learn of the change after the event.

How is Migration handled?
Migration will involve a short break in service whilst telephone lines are connected to new equipment in local exchanges. BT will tend to make the changes overnight, between 2400 and 0600, to minimise inconvenience, and anticipate maximum disruption periods as follows:

  •      PSTN/ISDN – 3 mins outgoing and 30 mins incoming
  •      Broadband – 5 mins outgoing and incoming

Will my telephone equipment need upgrading due to NGN/NGA?
In general no, as NGN (21CN) upgrades should only require new equipment to be fitted in exchanges. Most existing Customer Premises Equipment (CPE) should, with the exception of some (older) Digicoms, continue to work as normal unless connected via FTTP – in which case the CPE will need its own electrical power supply to operate (unlike legacy CPE that often runs off low voltage power supplied from the local phone exchange via copper wires).  

What is the impact on alarm systems of NGN?
There are two areas of potential impact on alarm systems connected to an ARC:

  • At Migration - The physical break in service whilst lines are transferred from old to new exchange equipment. This will usually take place overnight when networks are quieter. It may have an immediate impact on security, as many ATS are likely to detect a landline based transmission path fault during this time and report it to the ARC. Given the large numbers of lines possibly affected at any one time, ARC’s are unlikely to treat a ‘flood’ of such faults as an event needing individual notification to keyholders or the emergency services.

    Although possible, it seems unlikely that most criminals will be sophisticated enough to exploit this situation. However, at very high risk premises where customers do receive advance notice of Migration, it may be prudent to consider temporary alternative security measures, e.g. site manning/guarding.


  • Post Migration - When existing analogue CPE remains in use between a customer’s premises and the local exchange, data sent by it will need to be converted to IP form at the exchange, be converted back to analogue at its destination and possible also converted several times en-route. This conversion increases the end to end data transmission time (‘round trip delay’). The increased delay is small, but after migration non NGN compliant CPE, typically older Digicoms, may not recognise that a call has been connected, so could hang up and redial - possibly continuously. Depending upon the type of Digicom in use, this fault may be picked up and reported to customers by their ARC, or may just manifest itself in a larger than usual phone bill - reflecting a non NGN compliant Digicom trying, since Migration, to repeatedly, (unsuccessfully) dial the ARC to try and make a call.

Which Digicoms will be affected?
Any Digicom with a tolerance to round trip delay below the NGN (21CN) levels could be affected. However, without suitable testing Digicom suppliers do not reliably know which Digicoms are going to be affected or not, and older Digicoms may have no current manufacturer, or one with an interest in testing old (obsolete in their eyes) equipment.

Sourcing NGN compliant Digicoms
A combination of uncertainty over BT’s plans and difficulties replicating a loaded IP network, initially led to delays in testing Digicoms for 21CN compatibility. The British Security Industry Association (BSIA) led this process, and matters with BT have now been resolved or remaining issues identified and compatible replacement equipment identified. The BSIA are still working through suitable Digicom testing protocols/facilities with some NGN Telco’s.

What is the impact on alarm systems of NGA?
NGA was initially restricted to cities/major urban areas, but at the behest of Government is expected to be rolled out to most areas of the country over the next few years.

In terms of installation, NGA FTTC it is only likely to create the same brief problems as NGN (21CN) Migration at changeover. In terms of post Migration effects, FTTC is unlikely to create any issues for alarm signalling systems (other than round trip delay issues for older Digicoms); as existing copper cables from the cabinet to a customer’s premises will typically remain in-situ.

However, where FTTP is implemented it is possible that copper cables from a cabinet to customer’s premises will either not exist (new built premises) or existing cables may be removed, meaning that both Digicoms and other types of current alarm signalling equipment may cease to work. In such cases alarm users will either need to retain an existing copper cable link to the exchange for alarm use, or select a signalling product that can use fibre links, e.g. an IP capable transmission system.

What are your options?
Alarm users should talk to their alarm companies about this issue and, where a Digicom is now in use, consider a ‘future proof’ upgrade.

In doing so it should be borne in mind that Digicoms are a relatively insecure form of ATS; any break in service, e.g. intruders cutting a telephone line, not usually reported to the ARC - or if it is reported, not for many hours. Rather than buying a new Digicom, it may more cost effective, and certainly more secure, to opt instead for a form of ATS that incorporates frequent monitoring and fault reporting (to the ARC) of one signalling path (Single Path ATS) or both signalling paths (Dual Path ATS).

Will any of this affect my insurance cover?
If a policy contains an Intruder Alarm or Automatic Fire Alarm condition you may find that failure to maintain the alarm in full working order could jeopardise any claim that may occur related to that failure.

In addition you may be required to obtain insurer agreement for any changes to the system, e.g. a change of ATS. In this regard insurers are likely to prefer/recommend signalling products that have good fault reporting times, i.e. those that will report faults with a performance at, or near, to ‘grade’ 4. See ‘Hardfacts’ 3012: Intruder Alarms - European Standards for further information.

Key Action Steps

  • Watch out for news of NGN (21CN) or NGA enhancements in your area, especially those advised by your telecommunications provider
  • If unsure of your current alarm signalling, ask you alarm company to check and confirm it now
  • If a Digicom is in use, ask your alarm company to either provide a written statement of NGN (21CN) compliance or disclose their plans for a NGN compliant upgrade
  • Rather than installing a NGN compliant Digicom, consider the benefits of a better (fully monitored) signalling product and check proposed replacement alarm signalling with any interested insurer
  • If retaining a current Digicom, arrange for an immediate post NGN (21CN) migration check
  • Don't change your telecommunication provider without checking the possible impact on any current alarm signalling with your alarm company.

Sources of Further Information

Other Hardfacts in the Property Protection - Security series, which are available in our ‘Knowledge Store' at

BT -

British Security Industry Association (BSIA) - Tel 0845 389 3889 or

Your alarm company/telecommunications provider

Next Steps

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Please Note
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.

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