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Jargon Buster

The telecoms industry is full of acronyms and jargon, which can become confusing. To make sure you have a handle on your office phone system with the help of our useful office phone line glossary. If you have any further questions or want to understand a term not listed here, please contact us.


ADSL (Asymmetric Digital Subscriber Line) - This is the lengthy name for the technology that lets you receive broadband over your standard telephone line. It allows you to talk on the phone and surf the internet at the same time by splitting the signal on your telephone line in two. For this it requires a fully functional Microfilter (better described as a splitter). See also Microfilter

ADSL delivers fast download speeds but slower upload speeds.

ADSL2+ (Asymmetric Digital Subscriber Line 2+) - ADSL2+ extends the capability of basic ADSL by doubling the number of downstream bits. The data rates can be as high as 24 Mbps downstream and up to 1.4 Mbps upstream depending on the distance from the local exchange to the customer's premises.

Analogue Line - Analogue lines are the original lines used for making telephone calls. It commonly refers to a single line from your house/office to the point at which the line connects to the main telephone network (aka PSTN). Analogue lines are different from ISDN lines.

Anonymous Call Rejection - Rejects calls where the caller withholds their number.

Answer 1571 - Takes messages for you when you are unavailable or your line is engaged.

Anti-Virus Software - Anti-virus software is a program that searches your hard drive for any known or potential viruses. It will let you know if it finds anything, and can put the virus into quarantine until it can be disabled and safely removed.

Audio conferencing - A conference call is a telephone call in which the calling party wishes to have more than one called party listen in to the audio portion of the call. The conference calls may be designed to allow the called party to participate during the call, or the call may be set up so that the called party merely listens into the call and cannot speak. It is often referred to as an ATC (Audio Tele-Conference).

Auto Attendant - An automated system designed to guide a caller through the options of a voice menu. Typically set to answer and route incoming calls.


Bandwidth - Bandwidth is the term for the amount of data and the speed that it can be transferred over an internet connection. The amount of data is measured in bits, and bandwidth is usually measured in bits per second (bps). The necessary bandwidth is the amount of spectrum required to transmit the signal without distortion or loss of information. FCC rules require suppression of the signal outside the band to prevent interference.

Bar Use of Call Return - Means callers to your number cannot use the Call Return option (i.e. pressing '5' if you are engaged so that it calls them back)

Broadband - Broadband is the term for a high speed internet connection that is always on, so that you don’t need to constantly re-connect. A cable or wire is used to carry large volumes of data at high speed. It has a wide bandwidth, which can be either ADSL or SDSL. ADSL can suffer from vast bandwidth changes. See also Dial up & Contention Ratio


Call Barring - Stops certain calls being made from your phone. Allows you to bar a range of outgoing calls to prevent unwanted use of your phones e.g. premium rate calls or international calls

Call Deflection - Enables incoming calls to be identified and then forwarded to another destination before answering the call. Alternatively, incoming calls can be automatically forwarded to selected destinations dependent on their calling line identity.

Call Diversion - Allows you to divert calls to almost any phone - anywhere in the UK, most overseas destinations or a mobile phone! N.B. You will be charged for the forwarded part of the call.

Call Forwarding - Automatically transfers incoming calls to a different location, e.g. if moved to a different exchange area. Can either be admin provided or customer controlled. N.B. You will be charged for the forwarded part of the call.

Call Hold - A service feature that enables a user to retain an existing call, while accepting or originating another call using the same handset or phone device. The held call is tied to the handset that placed the call on hold and, therefore, can only be taken out of hold from the same handset.

Call Minder - Like Answer 1571, with the additional advantage of remote access and the option of having personalised messages.

Call Park - This service feature allows a user to place an active call on 'hold' (above) at one telephone handset and then retrieve the call, from any other handset within the same phone network. The call is effectively placed in a 'parking bay' and is allocated a parking bay number, e.g. 101. Users can then pick up another handset on the same network and type in the bay number to retrieve the held call.

Call Return - A service that will call your phone to let you know when an engaged number becomes free. It is normally activated by pressing '5' when you reach an engaged number. N.B. You will be charged for this service.

Call Sign - Allows you to distinguish between incoming calls on the same line.

Call Transfer - A service feature that allows a user to place a call on hold whilst, simultaneously, transferring the call to another destination. The destination can typically be both an internal or external telephone.

Call Waiting - Tells you if someone is trying to call when you’re already on the phone.

Caller Display - Displays the number calling you, unless the caller is using CLIR or COLR.

Caller Redirect (CNI) - A recorded announcement on a ceased line advising the caller of the new number to dial. This is a chargeable service.

Calling Line Identity Presentation (CLIP) - Lets you see the number of the person calling before you pick up the phone, enabling you to greet the caller in an appropriate manner.

Calling Line Identity Restriction (CLIR) - This prevents your directory number from being released at any time. Please be aware that there may be restrictions on its usage.

Choose to refuse – This enables you to bar the telephone number of the last answered incoming call.

CLI (Caller Line Identification) - The number of a specific telephone line.

CoLo - Colocation is often used in the data sourcing industry to mean off-site data storage, usually in a data centre. This is very important for businesses since the loss of data can be crucial for companies of any size.

Connected Line Identity Presentation (COLP) - This allows you to see the number of the line that you have been connected to.

Connected Line Identity Restriction (COLR) - This restricts the access of incoming callers to your identity. Please be aware that there may be restrictions on its usage.

Contention Ratio - This term is used to describe the number of individual broadband customers connecting to a single internet node at the local public exchange. High contention ratios will cause vast speed differences depending on time of day and number local users on line. Beware of busy periods, e.g. morning office hours and when people get home from work and log on.

Convergence - In recent years, changes in technology have meant that many businesses can now run both voice and data over the same Local Area Network, thereby causing them to ‘converge’. Cost savings are one benefit of Convergence but far more importantly there are significant productivity and efficiency gains to be achieved. VOIP, IP Telephony, Unified Messaging, Remote Working etc all come under the ‘Convergence’ umbrella.

Contract - The contract is the agreement you sign up to with a broadband provider, which may include a minimum contract period.

CPS (Carrier Pre-Select) - A system allowing clients to select their chosen ‘indirect’ carrier without the need of ‘smart boxes’ or least cost routing software.


Data - This is a general term for information sent back and forth over the Internet, whether it’s a web page, an email, music, images or any other type of electronic file.

Data Centre - A data centre (or data center or datacentre) is a facility used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression) and security devices.

Data Networks - An electronic communications process that allows for the orderly transmission and receipt of data. A data network is configured to transmit data only and provides transparent, symmetrical and un-contended or contended (5:1) bandwidth between two Ethernet ports in point-to-point, point-to-multipoint or meshed configurations. Many of our ISPs Data networks offer full UK coverage for short, medium and long distance data applications.

Dial-up - Dial-up is a way of connecting to the Internet through a modem. Your computer needs to be connected to a normal phone line and dials your Internet Service Provider (ISP) for access. Every time a connection is needed, the ISP must be called by your computer. The connection also tends to be much slower than broadband Internet, and while connected you cannot use your phone line. See also Broadband

DDI (Direct Dial Inbound) – A feature available on ISDN (see below) switchboards enabling callers to call people directly at their desks. DDI’s are mapped onto specific ISDN lines and the PBX is then programmed to direct the incoming DDI call to the specific extension or hunt group as required. Customers can rent a large volume of DDI’s whilst benefiting from renting an optimum number of lines based on required usage.

DEL - Stands for ‘Direct Exchange Line’

Directory Enquiries Only (DQR) – Upon request, your phone number will not be listed in the BT Phone Book, but is held on Directory Enquiries (118 services).

Download - When you are transferring data from the Internet to your computer, you are downloading. Download speed tends to be measured in Kilobytes per second (Kbps) or Megabytes per second (Mbps). See also uploading.

Download Restriction - Many broadband providers offer packages that place a cap or restriction on the amount of data you can download onto your PC – this helps them regulate how much bandwidth is being used and can therefore charge less for the service e.g. basic business broadband packages. If you should go over the limit, you may be charged for the amount you go over. See also Usage.


EFM - Ethernet in the first mile (EFM), also known as IEEE 802.3ah, is a collection of protocols specified in IEEE 802.3, defining the Ethernet in the access networks, i.e. first or last mile.

With wide, metro and local area networks already standardized, the EFM allows continuous standard Ethernet network across the globe, eliminating non-native transport such as Ethernet over ATM from the access networks.

Email - An email (short for Electronic Mail) is a message, which can be sent almost instantaneously to anyone with an email address, over the Internet.

Ethernet - Ethernet is the most widely used way of sending information from computer to computer at high speed. Unlike an old-fashioned modem, an Ethernet modem doesn’t have to turn the information on your computer into sound to transmit it along phone lines. It is a very common method of networking computers in a LAN (Local Area Network).

Ex Directory - Calls Offered (XDCO) - Not in the BT Phone Book, and not disclosed by Directory Enquiries. The operator will offer to call the customer for persistent enquiries. Please note that this is a chargeable service

Ex Directory - No Calls Offered (XDNC) - Upon request, your phone number will not be listed the BT Phone Book or held on Directory Enquiries.

Exchange - Essentially, an exchange is the building that provides your phone and broadband services in a certain geographical area. Each exchange serves thousands of phone lines, but you may not be eligible for certain broadband packages where you live because, for example, your local exchange has not yet been set up to receive it.

Exchange Line - In the UK we call lines that connect to the network provider exchange lines.


Feature phone (aka a system phone) – This is a phone with additional features for that particular phone system. Typically you are not able to swap these between different phone systems.

Frame relay - An interface designed to provide high speed packet transmission with minimum delay and efficient use of bandwidths.

Featureline - This is a BT specific service running over PSTN. Designed for small companies (typically max 3 users), it is a dated product that provides limited basic PBX functionality requiring one dedicated phone line per user. Featureline is not considered to be cost effective for 4 or more users.

Firewall - A firewall protects your computer against attacks from potentially harmful computer viruses and other threats. It acts as a sort of guardian, checking all of the data coming into your computer from the Internet and denying access to anything it sees as harmful.


Geographic number - A geographic number is a telephone number, from a range of numbers in the United Kingdom National Telephone Numbering Plan, where part of its digit structure contains geographic significance used for routing calls to the physical location of the network termination point of the subscriber to whom the telephone number has been assigned, or where the network termination point does not relate to the geographic area code but where the tariffing remains consistent with that geographic area code.

GB (Gigabyte) - A Gigabyte is a unit of measurement for both data storage and data transfer. For storage it equates to 1024 megabytes. For data transfer it equates to 1000 megabytes.


Hosted Telephony - An IP based phone system that is "Hosted" in a data centre. Customer sites connect to the hosted phone system via an internet connection that is generally either ADSL or SDSL but can be a leased line. Customer communication profiles are configured via a simple web based browser and individual users can control their own phone profile from any internet connection, with ease. Hosted Telephony is particularly beneficial for companies with two or more sites and can be used internationally.

The quality of the internet connection is critically important and it is recommended to keep the voice and data on separate internet connections.

HTTP (HyperText Transfer Protocol) - Essentially, it’s the language of the Internet - the set of rules for transferring text, images, sound and video. As soon as a user opens their web browser, they are making use of HTTP.

Hunt Group - Multiple phones allocated to a single DDI or extension number, thereby enabling an inbound call to be answered from any phone, within the allocated group of phones. i.e. accounts or sales department etc. Inbound calls can be configured to ‘hunt’ from one phone to another (until answered) or to be "broadcast" across all phones in the group, so they all ring at once.


IDA (In-Direct Access) - A coding used by carriers to facilitate calls via their networks.

Internet - The Internet is a worldwide collection of computer networks, working together to exchange data using a common software standard – usually HTTP. Nobody owns the Internet – so it is bound by few rules and answers to no single authority.

IP (Internet Protocol) - It’s a standardised method of transporting information across the Internet in packets of data. It is often linked to Transmission Control Protocol, which assembles the packets once they have been delivered to the intended location.

IP Address - IP is short for Internet Protocol, and an IP Address is a set of four numbers that are basically the virtual address of the computer you are using – a unique identifier if you like. Your Internet Service Provider (ISP) will assign your computer with a temporary IP address purely for when you are connected to the Internet. If you disconnect and reconnect later, you will be assigned a new IP address.

IP Telephony - Using Internet Protocol as a method of carrying voice calls. With IP, voice communications (in the form of IP packets) are routed directly from the origin to destination devices.

IP VPN - A virtual private network (VPN) is a computer network that uses a public telecommunication infrastructure such as the Internet to provide remote offices or individual users with secure access to their organization's network. It aims to avoid an expensive system of owned or leased lines that can be used by only one organization.

It encapsulates data transfers between two or more networked devices which are not on the same private network so as to keep the transferred data private from other devices on one or more intervening local or wide area networks. There are many different classifications, implementations, and uses for VPNs.

ISDN (Integrated Services Digital Network) – It’s a digital telephony service that gives better call quality, quicker connection times and DDI facilities. ISDN is generally provided to connect to a customer’s PBX. ISDN can also be used in Radio and was historically used for faster Internet connection before the advent of broadband.

ISDN2e – This digital telephony service is provided in pairs i.e. 2 channels/lines per ISDN2e. For offices with 2 - 8 concurrent users, ISDN2e allows for up to 8 simultaneous calls into or out of your business. The e stands for the European standard.

ISDN30e - This digital telephony service is provided over one large circuit (bearer/pipe) either as copper or in many cases fibre optic. Designed for larger offices whom expect to make or receive over 8 simultaneous calls. The minimum number of channels/lines one can have is 8 moving up to 30. Larger organisations can rent multiple ISDN30e’s should they require more lines. The e stands for the European standard.

ISP (Internet Service Provider) - Your ISP is the company that supplies your connection to the Internet. In our case, it would be our recommended ISP.


LAN (Local Area Network) – It’s a data network that connects computers, servers, printers etc together, generally within one physical location.

Landline (aka Analogue line or PSTN) - Your landline is the fixed analogue telephone line, which you can receive your broadband and phone services through. It is often used as a facsimile line. See also analogue line and PSTN.

Leased Line – It’s a dedicated private internet access circuit – provides secure, fast and unrivalled internet access.


MAC (Migration Authorisation Code) - Your MAC code is an identification number specific to your broadband connection. If you want to switch broadband supplier, your new Internet Service Provider (ISP) will need it to give you virtually uninterrupted service when they switch you over (usually your Broadband will only be unavailable for a few minutes). Please note: a MAC code is valid for 30 days, after this, if the change hasn't happened a new one will need to be requested.

MB (Megabyte) - A Megabyte (abbreviated to MB) is equal to 1,000 bytes, and is a standard unit of storage.

MIA (Managed Internet Access) – It is a highly reliable and flexible fixed Internet access service offered under the Surfwise brand. Customers can choose any speed between 1Mbps and 1Gbps and have the guaranteed peace of mind of 24/7 support. A huge advantage of MIA is that bandwidth to the Internet can be upgraded or ‘flexed’ at very short notice within an access class. This offers peace of mind to companies who cannot predict their needs.

Microfilter - Microfilters are small devices that you’ll have to plug into your home phone socket. Your modem and telephone both plug into the microfilter. All they do is stop your broadband signal interfering with your telephone calls.

Modem - A modem is a device that converts analogue signals (transferred by your phone line) into digital signals (to be read by your computer) and vice versa. This allows your computer to connect to the Internet via your telephone line. Usually, they’re directly connected to your computer, but some will allow your computer to connect to them wirelessly – which is just the job if you own a laptop or a number of Internet devices spread around your home. See also Router

MPLS (Multi Protocol Label Switching) – A flexible and cost effective way of providing a WAN.


No Directory Entry Required (NQR) - No directory entry is required. It is usually only available for lines connected to alarm systems, modems etc.

Non geographic numbers (NGNs) - Non-geographic numbers are telephone numbers available for private sale which, rather than being assigned to a particular telephone line or circuit, provide callers with a contact number which gives no indication as to the geographical location of the line being called. The owner of the number can retarget the NGN to any other telephone number including mobile, international and even other NGNs at any time therefore enabling them to take their calls on the move or at various locations at different times or simultaneously.

NTS - Number Translation Service: A number that is not geographically based, traditionally beginning with any other digit sequence except 01x and 02x.

Number portability - An agreement which allows for telephone numbers to be moved between telecoms companies.


Ordinary Directory Entry (O) – A directory entry held in the BT Phone Book and from Directory Enquiries (118 services)


PBX aka PABX - Public (Automated) Branch Exchange aka Switchboard aka Phone System.

POTS (Plain Old Telephone Service) – See analogue line or PSTN

Presentation Number - Enables the option of "masking" the main outbound number of a telephone line with a different number. This option is useful for call centres or companies that are located in obscure locations and don’t want end users to know their physical location or if they want to present a non-geographic number to the customers they are calling. For example, a company has a simple 0207 number but they want a 0845 number to be displayed to every end user that they call.

PSTN - Stands for ‘Public Switched Telephone Network’. This is the standard telephone service provided over basic analogue phone lines.

Pulse Metering - Sends 50Hz pulses to customers’ lines to indicate units of charge.


Reminder Call - Pre-programme alarm calls through your phone

Remote Call Forwarding (RCF) - A method for forwarding calls made to a ceased line to a new number, without the caller being aware that the call has been forwarded. The set up cost and monthly charge for this service is much more than for ‘Caller Redirect’. In addition the owner of the line has to pay the cost of the forwarded part of the call, as well as the exchange line rental for the ceased line (this is because the number of the ceased line cannot be reallocated to another user whilst RCF is in effect)

Ring Back - See 'Call Return'

Router - In essence, a router is a translator – it helps otherwise incompatible networks to communicate with each other and allows only authorised machines to connect to other computer systems.


SDSL (Symmetric Digital Subscriber Line) – Like ASDL, it the technology that lets you receive broadband over your standard telephone line. The advantage is that it provides the same speed/bandwidth in both directions, hence symmetric. It is especially useful for for companies needing to upload high bandwidth packets quickly such as data. It is a very common requirement with VOIP networks.

Short Message Service (SMS Services) – This is the text communication service component of phone, web or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices.

Service Maintenance Levels – These are the four service maintenance levels provided on all phone lines by Openreach.

It is now possible to Expedite repair from any Service Maintenance Level to any other for a one-off visit fee. For further details, please contact us.

Service Maintenance Level 1 – This service level is the basic level for residential phone lines only and is included in the line rental cost.

It operates during normal working hours (0800 – 1800 Monday to Friday exc. Public and Bank Holidays). If a fault is reported during these hours, the commitment is to clear it by the end of next working day + one e.g. a fault reported at any time between 00.01 – 23.59.59 on Tuesday would have a commitment time of 23.59.59 on Thursday

Service Maintenance Level 2 – This service level is the basic level for business phone lines and is included in the business line rental cost. It can be provided for residential lines at an additional cost.

It operates during normal working hours (0800 – 1800 Monday to Saturday exc. Public and Bank Holidays). If a fault is reported during these hours, the commitment is to clear it by the end of next working day e.g. a fault reported at any time between 00.01 – 23.59.59 on Tuesday would have a commitment time of 23.59.59 on Thursday

Service Maintenance Level 3 – This operates every single day including Bank Holiday. From

Monday – Friday it is from 07:00 - 21:00, whilst at the weekend (Saturday – Sunday) is operates from 08:00 – 18:00. It can be provided to both residential and business lines at an additional cost.

If the fault is reported by 12.59, the commitment is to clear it by 23.59.59 same day or the day of the appointment where later. If the fault is reported after 13.00, the commitment is to clear it by 12.59.59 next day.

Service Maintenance Level 4 – This operates all the time i.e. Monday – Sunday (inc Bank Holiday) 24/7. The commitment is a 6hr fix round the clock, 365 days a year. It can be provided to both residential and business lines at an additional cost.

SLA (Service Level Agreement) – This is the part of a service contract where the level of service is formally defined. In practice, the term SLA is sometimes used to refer to the contracted delivery time (of the service) or performance.

Smart Divert - This product is Call divert with remote access

SMTP (Simple Mail Transfer Protocol) - The standard Internet protocol for transferring electronic mail from one computer to another.

Sub Addressing (20 Octet) - This service allows calling parties to send up to 20 alphanumeric characters (except #) with the digits of the number they are dialling. Different combinations of characters can then be allocated to each device connected to a called ISDN 30e line. The characters sent would depend which piece of equipment is accessed, i.e. the phone will ring, access will be gained to PC, etc. Note: Terminal equipment must have the capability to send and/or receive Sub Addresses to use this service.

Speed - Speed is just that - the speed at which you can receive data. Broadband is far faster than the old dial-up connection that usually only worked at speeds of 56 Kilobits per second (Kbps). Business broadband packages offer speeds of up to 8 Megabits per second (8Mbps).

Streaming - Streaming lets you access a file – a video or music for example – as you are downloading it, rather than having to wait for the whole thing to download first.

Speed dials - This is the storing of regularly dialled numbers under short codes.

Switch - Engineers often refer to phone systems as switches.

Symmetric Digital Subscriber Line – See SDSL


Terminal - Telephone handsets are often referred to by engineers as terminals. All phones - all phones in the group ring together;

Three Way Calling – This allows you talk to two people at the same time - even if one of them is abroad!

TPS (Telephone Preference Service) - A service that bars calls to residential numbers that have been registered as “do not disturb”. Used mostly to prevent unwanted sales or marketing calls.

Trunks - Incoming lines from a public telephone operator (PTO).


Unified messaging – This enables you to access voice, fax, and text messages via one single email or telephone account. Typically a Microsoft Windows based panel on a PC running off a LAN. The unified messaging may provide visual control of voice and fax messages which are delivered to the PC node through a connection of the voice processor to the LAN’s file server.

Upload - When you are transferring data from your computer to the Internet, you are uploading (for example, when transferring pictures from your computer to a photo-sharing website). Upload speeds tend to be slower than download speeds and are measured in Kilobits per second (Kbps) or Megabits per second (Mbps). See also downloading.

URL (Uniform Resource Locator) - URL is the technical term for a website address (e.g.

Usage - Your usage is the amount of data you receive over the Internet. Many broadband providers offer packages that place a cap or restriction on the amount of data you can download onto your PC – this helps them regulate how much bandwidth is being used and can therefore charge less for the service e.g. basic business broadband packages. If you should go over the limit, you may be charged for the amount you go over. See also Download restrictions

User - That’s you.


Virus - A computer virus is a nasty piece of software that can copy itself and infect a computer without permission or knowledge of the user. They can be used for many purposes, including damaging files, discovering personal information, and even taking over your computer altogether.

Voice mail - The ability to receive information direct from a caller when you are unable to answer the telephone. Extremely versatile it allows you, as a basic feature, to provide callers with a personalised greeting and to give them the option of leaving a message. It is also possible to offer callers the opportunity to speak to an operator or a colleague.

VOIP - Stands for ‘Voice Over Internet Protocol’ - Voice translated into data packets and transmitted across an internet connection or network - just like any other file or email you might send. Upon reaching the other end data is transformed back into its original form and emerges like a regular phone call. (VOIP is critically dependent upon the speed of the packets across the internet and the correct assembly order once they arrive at their destination …for obvious reasons!)

VPN - Stands for ‘Virtual Private Network’ – A way of creating a private communications network over a public network (mostly the internet) using secure protocols (passwords, authentication methods etc).


Wireless Broadband - Wireless broadband offers high speed internet connection that uses radio waves to connect your computer to the Internet, doing away with the need for any physical wires to be connected to your computer.