We made this glossary and VoIPSure dictionary filled with helpful resources and articles to help you decode your business’ telecommunications.

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ACD – Automatic Call Distribution
Allows all incoming calls to be distributed equally amongst a group of people. Typically used in a call centre where operators (agents) log in to make or receive calls. ACD systems provide facilities for monitoring the agents’ performance and the performance of the call centre as a whole. An incoming call will be automatically routed to the first available agent, whether that is an agent who has been free the longest, or an agent that has just become free.
ADSL – Asymmetric Digital Subscriber Line – Broadband
Transforms the existing twisted copper pairs between the telephone exchange and the telephone socket into a highspeed digital line that is solely for access by the subscriber to the Club Connect Network. Speed of transmission is not the same in both directions; downloading is faster than uploading.
Analogue line
A single telephone line for used for analogue devices and broadband. These are typically what you will have at home.
Analogue device
A device that can be attached to an ordinary analogue telephone line, such as a telephone, fax machine, cordless phone, answering machine, modem etc.
Application or App
Applications are software programs that have been specially designed for mobile phones. They can include games, newsfeeds, media players, social networks, banking, etc. You name it, there’s probably an app for it. Some applications are free and may include advertisements, while others require a small payment.
A voicemail feature that allows callers to be automatically transferred to extensions or departments by dialling digits. A tone dialling phone is normally required to do this. For example, ‘press 1 for Sales, 2 for service’ etc.


The speed at which a circuit can carry data. The more bandwidth, the faster the data transfer, the lower the costs. Usually measured in Mbps (Mega bits per second).
A type of wireless transmission with a relatively short range (10 – 100 metres). This can be used to make a wireless connection between your telephone, computer, printer, car, headset etc.
A bolt-on is an additional mobile service that can be added to your main tariff. For example, additional texts, minutes or data can be added to your tariff to increase your inclusive allowance via a bolt-on.
This is effectively a packaged mobile deal. For example, with mobile phones you could get a text, minute and data bundle giving you inclusive minutes, SMS and data allowance for a predetermined fee or line rental. Bundles are also seen in fixed line, where service providers offer free calls for certain destinations / times of day for a monthly fee.


Call barring
The prevention of calls to certain destinations e.g. overseas calls or calls to premium rate numbers may be barred. This can be applied to the telephone system or at network level on the line.
Call forwarding
Also known as call diversion. By dialling a code, an extension user can divert incoming calls to another destination. The destination may be another extension, a group of extensions, the operator, or an external number, for example a mobile phone. Different types of diversion are usually possible, e.g. Diversion of All calls, Diversion on Busy, Diversion on no reply.
Call logging
Data recorded about calls made or received through a telephone system. This data can then be used for reporting.
Call management
The use of specialist software to analyse and report on call records, which are output from a telephone system and recorded on computer disk. The results can identify misuse, allocate costs to departments and verify the adequacy of resources.
Call park
A call can be parked by one user and then retrieved by another. Particularly useful when loudspeaker announcements are made, e.g. “Telephone call. Joe Smith dial 811”. If Joe goes to any phone and dials 811 he will get the call that has been parked there for him.
CDR – Call Detail Record
A digital file containing call records including CLI, date, time, number dialled, destination, duration and cost. A CDR will used to create and analyse bills.
Telephone service provider e.g. BT, Cable and Wireless, NTL etc. Carriers own their own infrastructure or network.
Cat 5
Abbreviation for Category 5. Strictly speaking, this is a specification for the transmission performance of a data cable.However it is commonly used to describe a building’s cabling system that allows the user to easily route voice and data circuits to any wall socket. It is designed to be network independent and to allow different computer and telephone systems to co-exist on the same cabling.
CCU – Central Control Unit
The box or cabinet housing the central equipment that controls the telephone system.
Coder / decoder – A technique used to compress/decompress speech or audio signals.
CLI – Calling Line Identity
The capture of the caller’s number. The CLI is associated to the line and is commonly known as the ‘telephone number’. The CLI can be presented on outbound calls and withheld. The user can also used an alternative CLI to present on their calls.
The joining together of more than two telephone users in a single call. Typically a call will be established between two persons; one will then hold the call, call a third party and then press a button to join all three parties in one call.
Contact centre
A progression of the call centre merging customer calls with other media such as internet and email in conjunction with CRM applications. A unified approach to customer contact, improving customer service levels leading to increased customer acquisition, satisfaction and retention.
CPE – Customer Premise Equipment
Equipment that is owned and supported by the customer.
CRM – Customer Relationship Management
A software application to deliver a single view of the customer. Customer records and information relating to the customer’s account are recorded in the CRM. Examples are Zoho CRM and HubSpot CRM.


DDI – Direct Dial Inward
A software application to deliver a single view of the customer. Customer records and information relating to the customer’s account are recorded in the CRM. Examples are Zoho CRM and HubSpot CRM.
DECT – Digital Enhanced Cordless Telephony
A technology that provides greater clarity and smaller handsets for cordless phones.
Delayed ringing
A feature often used to provide an overflow if the switchboard operator is busy or absent. Incoming calls are sent to the operator but other extensions have delayed ringing, so they will start ringing if the call is not answered after a pre-set time.


EFM – Ethernet in the First Mile
An access technology delivering dedicated synchronous and uncontended bandwidth to a site over multiple copper MPF pairs. This bandwidth can connect a site to the internet or to an MPLS network. EFM has industry standard SLAs.
Ethernet fibre
An access technology delivering dedicated synchronous and uncontended bandwidth to a site over a 100Mpbs or 1Gbps fibre bearer circuit. This bandwidth can connect a site to the Internet or to an MPLS.


Fixed Line
Fixed line is often the term used when referring to a solution or product that uses the PSTN network such as a telephone line and calls.
FTTC – Fibre to the Cabinet
A broadband access technology offering higher download and upload speeds than ADSL. Theoretically it offers up to 80Mbps download and 20Mbps upload but due to advertising rules quotes at 76Mbps and 19Mbps.
FTTP – Fibre to the Premises
A broadband access technology offering higher download and upload speeds than ADSL or FTTC. Theoretically it offers up to 330Mbps download and 30Mbps upload. There are no current defined advertising rules on the quoted speeds as it’s too new.


Group ringing
A group of extensions is rung by dialling a number. The group may be set as a ring group, in which case all of the extensions ring at once, or it may be set as a hunt group, in which case the system will find a free extension in the group to take the call.


A term used for cloud services where equipment is hosted on another premise such as a data centre. For example, hosted PBX will be accessed through user licenses paid by subscription. The handsets will be in the customer premises but the features and functionality will come from the platform hosted in a data centre.
Hot spot
‘Hot spots’ are locations where mobile phone users can connect to the internet using WiFi via a wireless access point. Many airports, hotels, even coffee bars are now equipped with this technology. Your device needs to have WiFi capability, but this is often built into smartphones.
Hunt groups
A means of finding a free extension to take a call. Calls are directed to a hunt group and will search for a free extension to take the call. Various hunting types are available: first free or terminal hunting will search for the first free extension in the group, so this person gets most of the calls. Circular or UCD (Uniform Call Distribution) hunting will share calls equally over the group.


Instant messaging
A service that allows you to ‘chat’ with another internet user in real time, by sending messages to each other. Modern messaging applications may allow users to send and receive attachments like photos and video.
IP address
A series of characters that uniquely identifies the terminal equipment, which is the origin or destination of data being transmitted. IPv4 is the current but now old variant with 32 bit address (an example is and the emerging standard is IPv6, which is a 128 bit address. IPv6 allows for a worldwide pool of 3.4×1038 addresses, or more than 7.9×1028 times as many as IPv4 address. IPv4 is a pool of 4,294,967,296 addresses which, as of 2013, is almost all used.
ISP – Internet Service Provider
An organisation set up in business to connect a consumer or business to the Internet.
ISDN – Integrated Services Digital Network
Digital lines over the PSTN. Businesses will tend to have digital lines and a digital telephone system. The benefits of digital is DDI, CLI, trunk-to-trunk transfer and faster data transfer. ISDN lines come in 2 flavours: ISDN2 – offering 2 channels of voice. If more channels are required, several ISDN2 bearers can be presented over one number; ISDN30 – ultimately a 2mb circuit divided into 30 channels. A minimum of 8 channels must be open; you can then increase the capacity 2 channels at a time without installing any more bearers until you reach 30.


Music on hold
An audio signal that is played to a caller on hold to reassure him that he has not been cut off. Typically music, it may be interspersed with advertising messages or could be simply a reassuring beep played every few seconds.


NGN – Non Geographic Number
Numbers that are not geographically located, typically 0300, 0500, 0800, 0808, 0844, 0845, 0870, and 0871. Premium rate numbers are also classed as NGN but priced more aggressively. These numbers are inbound only so do not have any equipment or lines associated with them. It is a cloud service.


PBX – Private Branch Exchange
On-premise telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network.
PAC Code – Porting Authorisation Code
A PAC code allows you to transfer an existing mobile phone number from one mobile phone network provider to another mobile phone provider so that if you change mobile phone networks you do not have to give everyone a new number. You can keep your existing mobile phone number. The process is termed mobile number portability, or number porting.
Porting / number porting
Porting is the name given to the process of transferring from one network provider to another network provider. Porting allows you to keep your number and is typically seen for mobile (O2 to Vodafone) or in fixed line (BT to another carrier).The process requires a LOA (letter of authority) from the end user.
PSTN – Public Switched Telephone Network
The world’s collection of interconnected voice-oriented public telephone networks, both commercial and government owned (AKA a traditional telephone network).
POE – Power over Ethernet Switch
A device that has several ports available. The switches come in 8 port, 16 port 32 port and 48 port. These switches also supply electricity to the device. See ‘network switch’ – it is the same except a POE also has electricity supply.
POE – Power over Ethernet Switch
A device that has several ports available. The switches come in 8 port, 16 port 32 port and 48 port. These switches also supply electricity to the device. See ‘network switch’ – it is the same except a POE also has electricity supply.


QoS – Quality of Service
The service level defined by a service agreement between a network user and a network provider, which guarantees a certain level of bandwidth and data flow rates.


RCF – Remote Call Forwarding
A method used for forwarding calls to a new number when a line has been ceased. Often seen with businesses who have moved premises and could not take their number with them. This service is less popular now with the ability to port numbers to other networks.
Roaming is a term referring to the way your mobile phone works when abroad so that you can make and receive calls, send text messages and use data services.
Routes data traffic. Routers can be wireless or wired. The router is the devise that sits between the Internet connection and your device.
RTC – Real Time Communications
The method of transporting voice over a data connection.


SIP – Session Initiation Protocol
A signalling protocol, widely used for voice and video calls over the internet. One SIP trunk allows for one channel of voice. This can be an alternative to ISDN or analogue channels. SIP trunks will typically be connected to a telephone system.
SLA – Service Level Agreement
An SLA is an agreement concerning a measurable level of service between the service provider and the service receiver.


TCP / IP – Transmission Control Protocol
Set of layered protocols that enable shared applications among PCs in a high speed communications environment.
A telephone exchange line to receive and make calls.
Trunk-to-trunk transfer
A facility that allows an incoming call received on one line to be transferred to someone on another line, i.e. both callers are external to the telephone system. Typical uses include transferring an incoming caller to someone’s mobile phone.


Unified messaging
A messaging platform that allows management of voice, fax and email from a single user interface (PC). Improves efficiency as all messages are presented from the one place to the user.


A voicemail system typically provides a central ‘answering machine’ for users of a telephone system. The user diverts his calls to the voicemail system, which will play a personalised message to a caller and allow him to leave a message for the extension user. Most voicemail systems also provide options for routing callers to departments or extensions and for giving out information to callers.
VLAN – Virtual Local Area Network
A protocol for separating devices on the same physical network.
VoIP – Voice over Internet Protocol
Voice calls being made over the internet, as opposed to the PSTN.


WAN – Wide Area Network
Improves cost and efficiency, as PC users in different sites may all access the same information as if they were all connected locally on the one local area network.
WiFi – Wireless Fidelity
WiFi is a WLAN (Wireless Local Area Network) technology. It provides short-range wireless high-speed data connections between mobile data devices (such as laptops and smartphones) and nearby WiFi access points (special hardware connected to a wired network).

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