Telecommunications jargon buster

4ESS

Class 4 toll switch made by Lucent.

5ESS

End office switch made by Lucent.

AAL – ATM Adaption Layer

This is the protocol used on top of ATM to support high-level service requirements, converting non-ATM bit streams into ATM cells.

AAL2 – ATM Adaption Layer 2

Used for carrying both CBR traffic and VBR traffic simultaneously, usually in support of voice-over-ATM.

Access Tandem

A tandem switch that’s used to interconnect between carriers for equal access. Typically this used to interconnect ILECs with IXCs, but now also includes CLECs.

ADPCM – Adaptive Differential Pulse Code Modulation

An ITU-TS standard technique for voice encoding and compression, which allows analogue traffic to be carried within a 32 Kbps digital channel.

AIN – Advanced Intelligent Network

An evolving and service-independent architecture that allows a carrier to create and modify telecommunications services for its customers quickly and economically.

A-Link

In the SS7 world, an A-Link is a signalling link that connects an STP to an SSP or an SCP. A-Links operate at a transmission speed of 56 Kbps.

ANSI – American National Standards Institute

UA non-governmental organisation that develops and distributes standards for transmission codes, protocols and high-level languages for suggested use in the USA

API – Applications Programming Interface

API is a set of routines, protocols and tools for building software applications. The API specifies how software components should interact. They’re used when programming graphical user interface (GUI) components.

ADSL – Asymmetric Digital Subscriber Line

Simply put, ADSL allows data to be transferred quickly over your phone line’s existing copper wires, as a form of common internet connection. Your broadband provider puts a splitter into your telephone wall socket so that you can run both your telephone and your internet connection at the same time.

In contrast with legacy ‘dial-up’ connections, ADSL internet connectivity allows you to access the WWW whilst chatting on the phone simultaneously. Nearly every home in the UK can get an ADSL connection, with a speed up to 8 Mbps. The further you live from the telephone exchange, the slower the connection speed.

ATM – Asynchronous Transfer Mode

An international standard for high-speed broadband packet-switched networks, operating at broadband digital transmission speeds. The technology is based on fixed-length 53-byte cells.

ATM includes protocols that specify how diverse kinds of traffic are transformed into standardised packets, whose transport can be managed uniformly within the network.

ALI – Automatic Location Identifier

A feature of 999 systems, which provides information to call agents, such as name, phone number and address.

AMA – Automatic Message Accounting

The network functionality that measures, collects, formats and outputs subscriber network usage data, to upstream billing and other operating systems.

ANI – Automatic Number Identification

Also known as Called ID, ANI is a service provided by local exchange carriers in which the phone number of a caller is sent to the receiving party’s telephone, between the first and second ring.

It’s one of several CLASS services, all of which require SS7 interoffice signalling.

Backbone

Part of a network used to connect smaller segments of networks together.

Bandwidth

The relative range of frequencies that can be passed by a transmission medium. Greater bandwidths mean a higher information-carrying capacity of the transmission circuit. Bandwidth is usually measured in Hertz (Hz) and is assessed as the number of bits that can be transferred each second.

BRI – Basic Rate Interface

The ISDN interface standard for single-line ISDN service. This standard provides for two message-bearing 64 Kbps B Channels for speech and data, plus a 16 Kbps D Channel for network signalling and data.

B Channel

Message-bearing 64 Kbps digital channel used for digital transmission of high-speed data and video.

BNS – Billed Number Screening

When consumers decide who can and can’t charge a call to their phone, based on an agreement with their local telephone company to screen calls.

Bit Rate

The number of bits transmitted over a telephone line per second.

B-Links, D-Links and B/D Links

The links interconnecting two mated pairs of STPs are referred to as B-Links, D-Links or B/D Links.

Broadband

The term used to describe a channel with more bandwidth than a standards voice grade channel. Broadband channels are used to carry multiple high-speed voice and data transmissions, on a common communications path.

B-ISDN – Broadband Integrated Services Digital Network

An evolving standard for the 2nd generation of integrated services digital networks. Broadband ISDN services employ packet switching to integrate voice and data services over a high-speed, packet-based infrastructure.

Bursty

Data transmitted in short and uneven bursts with relatively long silent intervals between.

Busy Hour

An uninterrupted 60-minute period during which the average volume of telecommunications traffic is at its maximum.

BHCA – Busy Hour Call Attempts

A measure of dynamic traffic calls that can be attempted in an average Busy Hour.

BHCC – Busy Hour Call Completion

A measure of dynamic traffic calls that can be completed in an average Busy Hour.

BLV – Busy Line Verification

A feature that allows an attendant to verify the busy or idle state of telephone lines, and to break into the conversation.

CDR – Call Detail Record

A billing feature of a telephone setup, which allows the system to collect and record information on outgoing and incoming phone calls, such as who made and received the call, what time it happened and how long it lasted for.

CPN – Called Party Number

When a call is set up over an ISDN network, SS7 send an initial address message, which contains the CPN as part of the ISUP protocol.

CCV – Calling Card Validation

The process of verifying that a calling card is valid and then processing a call to be billed to that account.

CAC – Carrier Access Code

The sequence that an end-user dials to access the carrier’s switch service. The codes are composed of 7 digits, in the form of 101xxxx, where xxxx is the CAC.

CCS – Centi Call Seconds

In telecommunications traffic engineering terminology, CCS represents one hundred call seconds or one hundred seconds of the telephone conversation. One hour of telephone traffic is equal to 36 CCS [60 x 60 = 3600, divided by 100 = 36].

CO – Central Office

The facility of a telecommunications common carrier, where subscribers’ lines are joined to switching equipment for connecting other subscribers to each other, locally and long distance.

Centrex

A type of phone service offered by local exchange carriers, which provides PBX-like functions to a group of users without the need for an actual PBX. Despite having individual phones connected to the central office, users can dial each other by extension, transfer calls and all the other features you might expect with a PBX system.

CIC – Circuit Identification Code

An SS7 term used to identify a particular circuit within a trunk group.

Circuit Switch

A switching system that establishes a dedicated physical connection between end points in a network, for the duration of the communication sessions.

C-Links

Links that interconnect mated STPS. They’re used to enhance the reliability of the signalling network in cases where one of multiple links are unavailable.

Compression

Reducing the size of the data, image, voice or video file sent over a telephone line, lessening the bandwidth needed to transmit the file.

CTI – Computer Telephony Integration

The combining of data with voice systems to enhance telephone service. Examples include the delivery of Caller ID information and the ability to access mail, all via a PC.

CLASS – Customer Local Area Signalling Services

A grouping of optional features to basic local exchange or enhanced telephony services that utilise the signalling system 7 (SS7) channel to carry data about a call. CLASS provides subscribers with the ability to screen and selectively reject, forward, trace and redial incoming calls. Caller ID is one example.

CPE – Customer Premise Equipment

The equipment that resides on the customer’s premises, such as a PBX or IAD.

Default Routing

The ability of the switch to continue the call based on the dialled number, when the SCP cannot be accessed due to abnormal circumstances.

DSP – Digital Signal Processor

A digital microprocessor that calculates digitised signals that were originally analogue (e.g. voice) and then sends the results on. DSPs are used in telecommunications for tasks such as echo cancellation, call progress monitoring, voice processing and for compression.

DN – Directory Number

A unique complement of digits associated with the name of a subscriber in a telephone directory – i.e. your phone number.

DLC – Digital Loop Carrier

An access provisioning system by which a telephone switch can remotely deploy telephony interfaces to customers. Typically, the connection between the switch and the DLC is via a digital or fibre connection, and user interfaces such as POTS (analogue) lines are deployed out of the DLC to customers.

DSL – Digital Subscriber Line

DSL is the technology that’s employed between a customer’s location and the carrier’s network, which enables more bandwidth to be provided by using as much of the existing network infrastructure as possible.

DSLAM – Digital Subscriber Line Access Multiplexer

A network device at a telephone company central office that receives signals from the multiple customer DSL connections, and puts the signals on a high-speed backbone line using multiplexing techniques.

Donor Exchange

The switch the directory number was initially ported from.

DTMF – Dual Tone Multi-Frequency

A term used to describe push button or touchtone dialling.

Echo Cancellation

A technique that allows for the isolation and filtering of unwanted signals caused by echoes from the main transmitted signal.

E-Links

Links that provide backup connectivity to the SS7 network if the ‘home’ STPs are unreachable using the A-Links.

End Office

The location where carriers place telecom equipment closest to the customer. Typically, this is where customers are provisioned. Class 5 switches are usually located here.

Equal Access

A condition where the local exchange access service offered by a carrier is made available in equal kind, quality and price to all long-distance companies.

ESS – Electronic Switching System

One type of Lucent’s family of stored, programme-controlled central office switches.

ETSI – European Telecommunications Standards Institute

The European counterpart of ANSI, tasked with paving the way for telecommunications integration in the European community.

EWSD – Electronic Digital Switching System (English translation)

A switching system made by Siemens.

Exchange

Another term of switch, commonly used in the UK to refer to a single-housed control centre for telecommunications.

Frame Relay

A packet-switched method of data communications provided by telecommunications carriers and internet service providers (ISPs). Frame relay can provide guaranteed bandwidth at no additional charge if the lines are open during periods of low traffic.

H.323

A framework of protocols for inter-working voice, video and data across an IP network.

Hot Swappable

The ability of a component to be added to or removed from a piece of equipment without powering down the device, providing maximum uptime.

Hunt Group

A series of telephone lines organised so that if the first line is busy the next line is ‘hunted’, and so on until a free line is found. Often used in an on-site PBX application where handsets replace available lines.

HFC – Hybrid Fibre Coax

Another term of switch, commonly used in the UK to refer to a single-housed control centre for telecommunications.

In-Band Signalling

A method of controlling information in a telecommunications network by using tones or other signals carried within the same band or channel as the information being carried. For example, telephone call tones can be used to control transmission, receipt or disconnection of the call.

IAM – Initial Address Message

An SS7 signalling message that contains the address and routing information required to establish a point-to-point telephone connection.

IAD – Integrated Access Device

An access device located on the customer premises that can handle both voice and data services.

ICP – Integrated Communications Provider

A company that provides bundled communications services, including voice and data services.

ISP – Internet Service Provider

An organisation that provides services for accessing, using or participating in the internet.

ILEC – Incumbent Local Exchange Carrier

This is the incumbent local phone company, which owns most of the local loops and facilities in a serving area, namely BT/Openreach.

ISDN – Integrated Services Digital Network

A switched network providing end-to-end digital connectivity for simultaneous transmission of voice and/or data over multiple multiplexed communications channels, and employing transmission and out-of-band signalling protocols that confirm to internationally-defined standards.

IoT – Internet of Things

A development in which everyday objects and applications have network connectivity allowing them to communicate with ourselves and each other.

IP – Internet Protocol

A network layer (Layer 3) standard for data transmission that performs addressing function and contains some control information, to allow packets to be routed through networks.

LAN – Local Area Network

A geographically localised network located on an individual organisation’s premises. LAN-enabled computer devices can communicate with each other as well as share and have access to peripherals such as printers, fax services, modem services and centralised databases.

LATA – Local Access Transport Area

A geographical area within which a divested RBOC is permitted to offer regional toll and access services.

Local Exchange

Geographic area determined by the appropriate state regulatory authority, in which calls generally are transmitted without toll charges to the calling or called party. Several local exchanges may exist within a LATA.

LCR – Least Cost Routing

A telephone system feature that automatically chooses the lowest cost phone line to the destination. The ‘lowest cost’ is determined by algorithms, equations and decision trees programmed into a PBX.

LIDB – Line Identification Database

Database deployed by RBOCs and all local telephone companies that contain all the valid telephone and calling card numbers in their regions and have the necessary information to perform billing validation.

Line Served by Switch

Any Directory Number that’s connected to the switch. The DN may be physical subscriber port of virtual DN.

LNP – Local Number Portability

The ability of telephone subscribers to maintain their phone numbers when they change local telephone companies.

LEC – Local Exchange Carrier

Any company authorised to sell local telephone services.

LERG – Local Exchange Routing Guide

Often used by carriers for network design.

Local Loop

The Local Loop is the telephone line that runs from the local telephone company’s end office switch to the user’s premises.

LLU – Local Loop Unbundled

The routing of alternative suppliers when lines hit the exchange, generally utilising Openreach copper to terminate to an NTE. The exchange then has space for the appropriate carrier to install their own equipment.

LRN – Local Routing Number

A 10-digit number used to uniquely identify a switch that has ported numbers.

LES – Loop Emulation Services

An ATM forum specification designed to emulate a customer’s local loop using ATM by extending class 5 service capabilities, along with high-speed data services, to customers.

M2M – Machine to Machine 

M2M can be used to describe any technology that enables networked devices to exchange information and perform actions without the manual assistance of humans.

Media Gateway

Communications switch equipment operating at the edge of multi-service packet networks.

MGCP – Media Gateway Control Protocol

An IETF draft standard for a protocol that allows Voice Gateways to control external call control elements. MGCP assumes a call control architecture where the call control ‘intelligence’ is outside the gateways and handled by external call control elements.

MF- Multi Frequency

In-band, analogue trunk signalling.

MMF – Multi-Mode Fibre

Fibre in which the ultrapure glass that forms the core transmission medium between 50 and 62.5 microns. This fibre has less carrying-capacity than single-node fibre.

Multiplexing

A process that concentrates traffic by combining many lower-speed transmission lines into one high-speed line, by splitting the total available bandwidth of the high-speed line into narrower bands (frequency division). Alternatively, this can be done by allotting a common channel to serve different transmitting devices, one at a time in sequence (time division).

MUX

A multiplexing device.

Next Gen – Next Generation

Used to describe emerging telecommunications or IT technologies.

NP – Number Portability

The ability for end-users to retain their telephone number when they change service providers.

Open Standard

A computer or communications standard whose technical specs are readily available to equipment manufacturers and other parties that want to incorporate the standard into their products or systems.

OSI – Open Systems Interconnection Model

An international set of rules for computer networking that creates open standards to allow a computer on any network to share information with any other computer on that network.

OAM – Operations, Administration and Maintenance

A group of network management functions that provide information and specifics to manage a system or network, such as performance info, network fault indications, and data and diagnosis functions.

Packet Switching

The technique by which a stream of data is broken into standardised ‘packets’, each of which contains address, sequence, control, size and error-checking information, in addition to the user data. Packet switches operate on this added information to move the packets to their destination in the proper sequence and again to present them in the correct continuous stream.

PVC – Permanent Virtual Circuit

This is a connection between end points that is defined in advance and needs little, if any, setup time. End points are normally defined for the carrier, by the customer, in advance.

POI – Point of Interface

The point in a network at which carriers’ interface with one another.

POP – Point of Presence

A long-distance company’s switch that’s connected to the local telephone company’s central office. The POP is the point at which telephone and data calls are handed-off between local telephone companies and long-distance telephone companies.

Port

The act of moving a telephone number from one network or technology to another one.

POTS – Plain Old Telephone Service

The traditional telephone services for the transmission of speech across the telephone network.

PRI – Primary Rate Interface

This is the narrowband ISDN interface standard for high-speed ISDN service.

PBX – Private Branch Exchange

Equipment used to switch telephone calls within a business or closed environment, and also for that environment to outside lines.

PSTN – Public Switched Telephone Network

The current narrowband-based telephone network that was designed for voice traffic.

PCM – Pulse-Code Modulation

An analogue to digital conversion technique. It’s used to convert voice for transmission over digital facilities. It’s also used to convert voice analogue data to digital data for transmission in a multiplexed voice and data stream, over T1 or other digital circuits.

Redundancy

Having backup systems available to provide uninterrupted continuous service in the case of a failure in the main system.

Scripting Language

Simplest form of a computer programming using nearly plain English commands. JavaScript is an example of a scripting language.

SIP – Session Initiation Protocol

A protocol for transporting call setup, routing, authentication and other feature messages to end points within the IP domain, whether those messages originate from outside the IP cloud over PSTN resources, or within the cloud.

Trunk

The line of communications between switching systems, also used in reference to SIP or SIP trunks.

Unbundled

As part of the telecom deregulation, BT was required to unbundle their network elements and lease them at wholesale rates to alternative suppliers.

UC – Unified Communications

A term used to refer to combined communications methods, in a single solution. Telephony, mobile, email etc.

UM – Unified Messaging

Voice, fax, email, image and video all on one platform, available to consumers via a local area network (LAN).

VC – Virtual Circuit

A link between two or more end stations on a packet switch mesh network. It provides temporary or dedicated connection-oriented sessions between two end points – the defining characteristics are a pre-defined path through a network that has many paths.

VR – Virtual Reality

Virtual Reality refers to the use of computer technology to create a simulated environment. Rather than viewing the experience on a screen, VR places the user within the experience.

VoIP – Voice over IP

The process of transmitting voice traffic across an IP-based packet.