Asymmetric Digital Subscriber Line - the broadband technology used to deliver standard copper broadband products. It is designed to be able to run over long copper cable lengths, sacrificing speed for distance, allowing wider data coverage with fewer DSLAMs across the network.


Backhaul Network Services. Backhaul Network Services (BNS) is a solution for communications providers who want to backhaul data from a number of outlying Local Loop Unbundling (LLU) or mobile Base Station Controller sites to their own network.


Calling Line Identity (also known as Caller ID, caller identification, CID, Calling Number identification, or CNID). A telephone service that transmits a caller's number to the receiving telephone equipment during the ringing signal, or when the call is being set up, but before the call is answered.


Digital Access Carrier System (also known as 0+2 Pair gain system). Modern ISDN technology based digital systems, made up of two normal subscriber lines over one copper pair.


Digital Access Signalling System. Our original ISDN30 offering used this as a signalling standard.


Direct Dialling In. A facility that lets callers dial direct into a firm's PABX extensions as if they were normal public telephone numbers. Most of our offices have DDI facilities.


Dynamic Line Management - this is a system that monitors each line in real time based on a set of rules within a defined policy to change the parameters of the line to achieve the best balance of speed and line stability. There are currently three policies which have different rules for managing the lines, Speed, Standard and Stable.


Digital Main Switching Unit. These are the original long-distance exchanges. They are System X switches with the capacity to handle 30,000 simultaneous calls each. Every DMSU is connected to all the other DMSUs. This involves a much smaller number of links than would be required to link together the Digital Local Exchange.


Digital Private Network Signalling System. A network protocol used on digital trunk lines for connecting two PABX. It supports a defined set of inter-networking facilities.


Distribution Point. A point within a network where the cable or fibre terminates. This provides a point of entry for engineers to terminate or test the network. Typically these points are located on telegraph poles.


Digital Subscriber Line Access Multiplexer. A network device, located in the telephone exchanges of the service providers,


Dual Tone Multi Frequency. Used for telecommunication signalling over analogue telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching centre.


European Telecommunications Standards Institute. An independent, non-profit, standardisation organization in the telecommunications industry in Europe with worldwide projection. ETSI has been successful in standardising the Low Power Radio, Short Range Device, GSM cell phone system and the TETRA professional mobile radio system.


Ethernet Access Direct. Offers permanently connected, point-to-point high speed data circuits that provide a secure and un-contended Ethernet service for Communications Providers between flexible network and customer nodes.


Ethernet Backhaul Direct. Offers permanently connected, point-to-point high speed data circuits that provide a secure and un-contended Ethernet backhaul service for Communications Providers over a defined network infrastructure.


Fibre to the Cabinet - the term for the supply of data services over a fibre optic cable running between the local exchange and the local street cabinet, then using existing copper cable to deliver the data to the end user’s premises. In FTTC, the device which translates the data into a signal that can be carried over copper wire, the DSLAM, sits in a local street cabinet, rather than in the local exchange.


Fibre to the Premises - the term for the supply of data services over a fibre optic cable running between the local exchange and the end user's premises. This technology completely replaces the need for copper cabling within the Openreach network.



  • AN – Aggregation Node
  • BFT – Blown fibre tube
  • CBT - Connectorised block terminal
  • CMJ – Compact multi-function joint (used as small plitter or intermediate joint)
  • ELM – External locking mechanism (locking bollard)
  • FDP – Fibre DP
  • MMJ – Medium multi-function joint (used as medium splitter or intermediate joint)
  • NJ4A – Node Joint 4A
  • OTDR – Optical Time Domain Reflectometer
  • PM – Pole mounted
  • PMC – Pole mounted closure (interim pole mounted transition joint)
  • SN – Splitter Node
  • SST- Standard single tube (small profile cable)
  • ULW – Ultra Lightweight (36 fibre cable)
  • UN2 – Universal node 2 (used as large splitter or intermediate joint)


Fibre to the (Cabinet - FTTC, Premises - FTTP, etc). Any broadband network architecture that uses optical fibre to replace all or part of the usual metal local loop used for last mile telecommunications.


Giggabit Passive Optical Node


High Speed Digital Subscriber Line (also known as High-speed Digital Subscriber Loop). A copper delivered service on Copper Wideband Serving Section (CWSS). It is subject to reach limitations and is used primarily to provide 2 Mbit service to singleton sites.


Integrated Services Digital Network. A digital network that lets a whole host of services be carried together on the same circuits. Considered an extension of the public switched telephone network, the key similarity is that it lets any two compatible pieces of connected equipment talk to each other. ISDN can carry any form of data, such as voice, video and computer files.


Local Area Network


Lead To Cash (provisioning). The lead to cash process goes from initial contact, to sale, to service delivery, to payment collection.


Local Loop Unbundling. Lets communications providers offer the full range of voice and broadband services, without having to route through our main network.


Main Distribution Frame. A point in a telephone exchange where cables from outside can be connected to the exchange equipment.


Multiple Subscriber Number. An ISDN version of Direct Dial In.


A service within the Openreach network for distributing live television broadcasts to many users over broadband at the same time, in real time.


Next Generation Access (also known as Super Fast Fibre access). Our programme that is dedicated to shaping tomorrow's communications environment. We work with communications providers, the regulator, industry and other stakeholders to ensure that we build a clear picture of an access network that's fit for the future.


Network Termination Equipment version 5 - also commonly known as the master socket, this is the copper termination point within the end user's premises and the place where the GEA over FTTC SSFP is installed. The master socket marks the demarcation point between the Openreach network and the end user's home network with respect to voice wiring.


Network Terminating Equipment. Equipment that is located in the home or office. Examples are set top boxes and LAN.


Network Terminating Point. The place where the network ends.


Openreach Handover Point. Mainly located in Metro Nodes, which are the breakout point for our Bulk Transport Link and Ethernet Backhaul Direct products.


Openreach Network Backhaul Service. Offers connectivity between a communications providers' equipment (installed within Co-location, Netlocate or BT Locate at a BT MSAN Site) and their equipment (installed within Co-location, Netlocate or BT Locate at either the nearest BT MSAN Site, BT Metro Node Site or another BT MSAN Site or Metro Node Site which is within a distance of 15 radial kilometres of the first BT MSAN/Metro Site).


Private Branch Exchange. A telephone exchange that serves a particular business or office.


Primary Cross-connection Point - this is the local street cabinet in which cables extending out to local distribution points are aggregated and connected to larger copper and fibre optic cables to move the voice and data signals to and from the local exchange. The number of connections managed in a PCP depends on the number of end user premises in an area, but is usually several hundred (200-400) lines.


Plain Old Telephony Service (also known as an analogue telephone line). The basic services provided over the Public Switched Telephone Network (PSTN).


Public Switched Telephone Network. It was originally a network of fixed-line analogue telephone systems but the switching (or telephone exchange) element of the PSTN is now digital. The mobile telephony networks are considered to be part of the PSTN.


Power Supply Unit (power supply). A power supply unit is a device that supplies electrical power to a device or group of devices.


Passive Optical Node (Network)


Symmetric Digital Subscriber Line (also known as Symmetric Digital Subscriber Loop). Uses a single wire pair to carry a few Mbit/s of data. However, unlike ADSL, upload and download speeds for the user are the same (hence symmetric versus asymmetric).


Superfast Fibre Access - the marketing term used to describe Openreach's fibre optic access products


Single Number Direct Dialling In. An individual number DDI range, which means that for incoming calls the network will send, as default, 6 routing digits to the customer equipment so that calls can be directed to the correct channel.


Telephony over Passive Optical Networks. A technology that we have designed, it is made up of slim fibre optic cable instead of lots of copper wire pairs.


Very high bit rate Digital Subscriber Line - the broadband technology used to deliver the higher speeds associated with FTTC compared to standard copper broadband products which are delivered over ADSL. VDSL is designed to work on shorter lengths of copper cable.


Virtual Interconnect Circuit. Allows for migration of interconnect routes from the DLE to the NGS.


Virtual Local Area Network - a subdivision of the capacity within the network representing the "pipe" provided for a single end user’s data traffic through the Openreach network.