Telecoms Jargon Buster Let the experts do the talking.

Here at DRC, one of the three pillars we stand by is to keep things simple. We understand that at times, the world of telecoms can be full of jargon and tricky to navigate. Our aim is to listen to your business needs and plans, and then recommend a straightforward solution that is both fit for purpose now, but will also support your business growth. We hope you find this guide useful and if you need any extra support regarding terminology, or want an open and honest chat about your own business needs, get in touch.

Stands for ‘Asymmetric Digital Subscriber Line’. A popular, older type of broadband that works through the copper wires of existing phone lines and mainly used for home broadband and very small businesses who are cost conscious.


Analogue Line
A simple copper phone line with a maximum data transfer rate of 56k. Used for phone calls, alarm monitoring, fax and PDQ machines but more commonly for ADSL broadband connections. There are many areas in the country where they are no longer sold, and the plan is for a full UK switch off by 2025.


Anonymous Call Rejection
Rejects incoming calls where the caller withholds their number. This can be set up on a ‘whole account’ basis or at a DDI level.


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, meaning each caller is delivered to the right place to increase business efficiency.


A measurement for the maximum data transfer rate of a network, including an Internet connection. In simple terms it’s how much data can be transmitted in a given amount of time and is typically expressed in bits per second. Kbps is Kilobits per second and Mbps is megabits per second. K being 1,000 and M being 1,000,000. Therefore, a 70Mb connection (70,000Kpbs) is receiving 70 million bits of information per second. See ‘Bits vs Bytes’ below.


Bits vs Bytes
Bits are generally used to measure data transfer rates (see bandwidth) and Bytes are used to measure data capacity and storage. 1 Byte consists of 8 bits. In written form a Byte is depicted with a capital B and a bit is depicted with a lower-case b. For example, 1MB means 1 Megabyte (size) but 1Mb means 1 Megabit (speed).


Stands for Busy Lamp Field. A BLF is a small light on an IP phone that shows you whether an extension is on a call or not.


A term used to describe internet access. This a generic term that covers an internet connection using any access method other than ‘dial up’ (aka narrowband). In reality, most people would now consider basic ADSL to also slot into the narrowband category since most of the population has become used to much faster internet connections via Fibre to the Cabinet, Fibre Leased Lines and 4G.


Call Barge or Call Monitoring
This facility allows specified users to join an active call and therefore create a three-way call. The person barging in can choose to mute their handset before joining the call, thus creating a ‘silent call monitoring’ scenario. There are normally a set of users (supervisors) that are set up to be able to ‘barge’ in on active users (monitored users).


Call Barring
Removes the ability for a phone or system from dialling certain destinations or codes. Normally used to reduce costs and/or prevent fraud.


Call Diversion
Allows you to divert calls to almost any phone - anywhere in the UK, most overseas destinations or a mobile phone.


Call Hold
A service feature that enables a user to retain an existing call, while accepting or making another call using the same handset or phone device.


Call Paging
A feature that allows a user to make an announcement to numerous users simultaneously using the speaker on each handset. This is a one-way communication, i.e. only the caller can speak. Think of it as similar to a tannoy system in a warehouse.


Call Pickup
The ability to take a call that is currently being presented on another phone or phones. The ringing phone(s) need not necessarily be in the same physical location as the user wishing to pick up the call. In this instance the user would be aware of another ringing phone by an indication on their own handset.


Call Queue Group
A Call Queue Group is essentially a Hunt Group with the ability to queue calls, should all users in the Hunt Group be busy. Call Queue Groups would normally have music/messages played to callers whilst they are held in the queue. As users become free, calls will be passed through, sometimes called Calls to Pass.


Call Transfer
A service feature that allows a user to place a call on hold and then transferring the call to another destination. The destination can typically be either an internal or external telephone. The transfer can be attended (you announce the caller) or blind (the caller gets put straight through with no introduction)


Call Waiting
A tone or message that alerts you that someone is trying to call when you’re already on the phone.


Caller Display
Displays the number calling you assuming the caller has not chosen to withhold their number.


Cellular Network
The cellular network is a communication network that uses fixed data transceivers (mobile masts) to connect cellular devices, such as mobile phones, to the internet.


Stands for ‘Calling Line Identification’ – sometimes called Caller ID. A CLI allows the recipient of a telephone call to identify the number of the incoming caller. In the UK, an outgoing caller can withhold their number to the recipient by dialling 141 before dialling.


Conference Calling
Allows multiple callers to participate in one phone conversation simultaneously. Users all call one number and may have to enter a PIN. Conference calls can usually be recorded.


Contention Ratio
A term used to describe the number of individual broadband customers connecting to a single internet node at the local public exchange. Different contention ratios will cause vast speed differences, as higher ratios normally equate to slower speeds. This can often vary depending on time of day and number of users online.


Historically, Voice & Data networks were kept entirely separate. However, in recent years, changes in technology have meant that many businesses can now run both voice and data over the same LAN, 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 Comms, Remote Working etc. all come under the ‘Convergence’ umbrella.


Communications Provider. Any company able to provide telecoms products and services.


Customer Premises Equipment. Meaning devices, extension sockets, cabling, routers, switches etc, which are on site at a customer location. Typically the responsibility of the customer to maintain.


Stands for Communications Provider Identity. This is a unique identifier allocated to communications providers by Ofcom.


Stands for ‘Direct Dial Inbound’ – allows users to rent individual phone numbers without the need to rent individual lines. Customers can choose to rent a large volume of DDIs without having to pay for a user for each of these – each DDI can be programmed to divert to a specific end point.


Stands for ‘Digitally Enhanced Cordless Telecommunications’. A technology used to link cordless mobile handsets to a wired telephone system. Usually a perfect solution for users not tied to a desk, such as in a warehouse or hospitality environment.


Another term to describe an Analogue Line and stands for ‘Direct Exchange Line’


Directory Enquiries.


Ethernet in a premise is a cable type, but Ethernet is also used as a term for a Leased Line.


Ethernet Circuit
See ‘Leased Line’


Exchange Line
Another term to describe an Analogue Line.


A BT specific service running over the PSTN (telephone network). Designed for small companies (typically max 3 users), it is an outdated product that provides limited basic PBX functionality requiring one dedicated phone line per user.


Fibre To The Cabinet (FTTC)
This is a generic term for any broadband service that uses fibre optic cable, in place of traditional copper wiring, to connect a telephone exchange to the 'green cabinets' in the surrounding roads. This means that copper wires are only used in the last few hundred metres between a green cabinet and a customer's premises. Unlike copper, fibre is extremely fast, does not suffer from signal loss over distance, or is susceptible to interference caused by severe weather. Therefore, fibre can provide much faster download and upload speeds and greater bandwidth.


Fibre To The Premises (FTTP)
This means that the entire broadband service is provided on fibre optic cable, from the telephone exchange into the premises. Typically, you can expect noticeably higher speeds on FTTP services than FTTC.


A firewall protects a network from threats, virus, hacking, or unapproved access. It’s also used to allow access in to a network for remote working.


Hosted Telephony / Hosted VoIP
Hosted Telephony (aka Hosted IP Telephony) is an IP based phone system that is "hosted" in a data centre. Customer sites connect to the hosted phone system via an internet connection. All the intelligence of the phone system is held within the data centre and the on-site equipment is controlled by the central system. Customer communication profiles are normally configured via a 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. Hosted Telephony licenses often now include free calls.
The quality of the internet connection is critically important, and it is often recommended to keep the voice and data on separate internet connections.


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 departments. 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.


Stands for ‘Internet Protocol’. 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.


Stands for ‘Integrated Services Digital Network’. ISDN is generally provided to connect to a customer’s on premise PBX.
Openreach have announced plans to discontinue this service by 2025.


Provided in pairs i.e. 2 channels per ISDN2e line. The majority of customers would get a maximum of 4 pairs before moving up to ISDN30e. The e stands for the European standard.


Provided over one large circuit (bearer/pipe) either as copper or in many cases fibre optic. The minimum number of channels/lines one can have is 8 moving up to 30. Larger organisations can rent multiple ISDN30es should they require more lines. The e stands for the European standard.


Stands for Interactive Voice Response. A facility that allows a computer to interact with users through the use of voice and/or tones input through a keypad. Often used with Auto Attendants and voicemail services.


The constant jump from good to bad latency, causing a poor / intermittent service for callers.


Stands for ‘Local Area Network’ – a data network that connects computers, servers, printers etc. together, generally within one physical location. This can be either wired, or wireless, or a mixture of both.


A measure of delay. In a network, latency measures the time it takes for some data to get to its destination across the network. It is usually measured as a round trip delay (RTD)- the time taken for information to get to its destination and back again. Network latency is measure in milliseconds. A telephone call requires a latency of 80ms or less to work effectively. Above that and the speech delay becomes noticeable to the human ear and is no longer an effective mechanism for a conversation.


Leased Line
A dedicated private internet access circuit – provides secure, fast and uncontended (not shared) internet access for the exclusive use of the end user. Historically these have been very expensive, but costs are coming down rapidly, putting leased lines within the reach of many smaller businesses.


Stands for Local Loop Unbundling. The process whereby the network operators (Openreach and Kingston Communications) make the local network available to other companies, so that they may in turn rent them to end users.


Stands for ‘Machine to Machine’. M2M is a technology that allows a user to remotely connect to an M2M device over the cellular network.



Stands for ‘Metallic Path Facility’ and is used by LLU providers to offer broadband and voice services.


Stands for ‘Multi Protocol Label Switching’ – A flexible and cost-effective way of providing a WAN. Used to transport data over public services whilst keeping the data private.


Stands for Non-Geographic Number. A number that normally begins with 03, 08 or 09, and is therefore not linked to a specific geographic location (or, more accurately, a telephone exchange)


Ofcom is the regulatory body for communications services in the UK. Amongst other things they are responsible for setting out various rules and regulations to which the communications industry must adhere.


Packet Loss
Usually a symptom of inadequate bandwidth, this is when traffic gets ‘lost’ on its way to the destination or on the way back. This results in more packets being sent and gives a poor user experience.


Public (Automated) Branch Exchange also called a Switchboard or Phone System. A phone system that is located on the end user’s premises, to which are connected the incoming lines and telephone extensions. The system manages the routing and handling of inbound and outbound calls, as well as internal calls. Historically all on a customer premises, now we hear more about Hosted PBX (see Hosted Telephony)


Stands for ‘Power Over Ethernet’. PoE is a method of supplying a device with power using an Ethernet connection and not a separate power supply.


The process by which a specific telephone number or numbers are moved from one supplier to another. This enables end users to change suppliers or telephony platform whilst retaining their phone number.
The porting of a number is led by the gaining communications provider, and the end user should expect to be asked to sign a document giving their authority to port the number.


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 may have a number beginning 0207 but they want an 0800 number to be displayed to every end user that they call.


Stands for ‘Primary Rate Interface’ – see ISDN30e.


Stands for ‘Public Switched Telephone Network’. This is the generic term for the public telephone network provided by multiple carriers.


A device that is used to connect you to external connectivity, connecting to a supplier network and ‘routing’ traffic to its destination.


Stands for ‘Software Defined Wide Area Network’, using software on the router or in the cloud to control the network and give new controls and visibility.


Stands for 'Session Initiation Protocol'. It is essentially a communications protocol used to set up and clear down sessions with one or more users over the internet. Can be used in a multitude of scenarios, but most common is in the initiation and termination of Voice over IP calls, or to connect a customer’s on-premise PBX to the PSTN.


SIP Trunk
In simple terms, an internet phone line. A SIP trunk is a virtual link between an IP PBX (usually at a customer site or data centre) and a network operator, which is designed to carry private SIP traffic (VoIP phone calls). Each trunk contains SIP channels and each phone call requires one channel. There is no limit to how many channels can be provided on one SIP trunk. SIP trunks are much cheaper to rent than traditional phone lines and also offer vast scope in terms of DDI number allocation and management.


Stands for 'Service Level Agreement' - 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.


Stands for ‘Shared Metallic Path Facility’ and used by LLU providers to offer broadband services.


Stands for ‘Short Messaging Service’. It’s another way of saying text message.


Stands for ‘Simple Mail Transfer Protocol’. The standard Internet protocol for transferring electronic mail from one computer to another.


Stands for ‘Single Order Ethernet Access’. It’s a new technology that allows you to have a high speed internet access without the need for a separate analogue phone line.


Unified Communications
Enables you to access voice, video call, fax, and text messages via one single email or telephone account.


VoIP (see also Hosted Telephony)
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!)


Stands for ‘Voice Over LTE’. VoLTE is a method of delivering telephone calls using a cellular data connection. A VoLTE call is a VoIP call using the UK’s 4G / 5G network rather than a fixed line connection.


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.)


Stands for ‘Wide Area Network’ – Connects multiple LANs together, typically via VPNs over broadband and/or Leased Lines – (The internet is a WAN)




Learn more about industry-specific jargon, or simply call us for friendly no-obligation advice. Call us now.