Glossary of telecoms terms

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2G (Second Generation)
2G is a network protocol that handles phone calls, basic text messaging, and small amounts of data over a protocol called MMS.

3G (Third Generation)
3G is a mobile communications standard that allows mobile phones, computers, and other portable electronic devices to access the Internet wirelessly. 3G provides speeds up to 384 Kbps when a device is stationary or moving at pedestrian speed, 128 Kbps in a car, and 2 Mbps in fixed applications.

4G (Fourth Generation)
4G is a network protocol for mobile use, including smartphones and tablets. Connection speeds need to have a peak of at least 100 megabits per second, and for more stationary uses such as mobile hotspots, at least 1 gigabit per second. Also see LTE below.

ADSL (Asymmetric Digital Subscriber Line)
This allows more data to be sent over existing copper telephone lines, when compared to traditional modem lines. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). See below for the difference between bits and bytes and what both of these mean.

ADSL2+ (Asymmetric Digital Subscriber Line 2+)
This is an extension to ADSL broadband technology that provides subscribers with significantly faster download speeds when compared to traditional ADSL connections. Maximum speeds achievable  are 24Mbps download and 2.5 Mbps upload.

Analogue Telephone Adapter
This small adapter enables a standard analogue phone to connect to a VoIP network so it can make and receive calls. VoIP is Voice over Internet Protocol, using the internet to make phone calls.

Bites and Bytes
Bits and Bytes both measure amounts of data. However, they are typically used in two different contexts.
Bits, kilobits (Kbps), and megabits (Mbps) are most often used to measure data transfer speeds. This may refer to how fast you are downloading a file, or how fast your Internet connection is. For example, if you are downloading a file on cable modem, your download speed might be 240Kbps. This is much faster than a dial-up modem, which maxes out at 56Kbps.
Bytes, on the other hand, are used to measure data storage. For example, a CD holds 700MB (megabytes) of data and a hard drive may hold 250GB (gigabytes). The other important difference is that bytes contain eight bits of data. Therefore, a 240Kbps download is only transferring 30KB of data per second. However, kilobytes per second is not as commonly used as kilobits per second for measuring data transfer speeds. After all, using kilobits per second (Kbps) makes your connection sound eight times faster!
It is important to know that bytes are abbreviated with a capital B, where as bits use a lowercase b. Therefore, Mbps is megabits per second, and MBps is megabytes per second. So 8Mbps is equal to 1MBps.

Call Barring
This feature allows you to stop certain types of calls being made or received by your phone. Call types include

  • UK National
  • International
  • Mobile
  • Premium Rate
  • Directory Enquiry services

Call Deflection
Responds to an incoming call by deflecting the call to another number without answering

Caller Display
Displays who is calling

Call Diversion
Call Diversion enables you to have all your calls diverted to another number – this can be anywhere in the UK, most overseas destinations or a mobile phone.
You can choose to divert all calls, divert on no reply or divert when the line is busy. A message is given to the caller when diverting on no reply, in case the divert-to number returns an engaged tone.

Calling Line Identity Presentation (CLIP)
Display caller's telephone number

Call Minder Standard custom (1 Mailbox)
This exchange-based service answers calls, and records messages, on no reply or engaged. Up to 30 messages can be stored; maximum message length is 5 minutes.
If a message has been recorded while the line is engaged, Call Minder calls your number at 10 minute intervals for up to 60 minutes to invite you to listen to the message.
An interrupted dial tone alerts you to a waiting message. After listening, the message can be heard again, saved or deleted.
Call Minder can be accessed remotely to retrieve messages, to change service options such as the number of rings before answer, personal greeting and PIN. (For security, a PIN can only be changed from the registered line).
Call Minder can take messages from a digital mobile phone. This works in the normal way, by dialling 1571 from a mobile phone. Call Minder sends a voice alert, or if it can't get through it will send a text message to inform you that you have a new message.
Call Minder alerts customers with email accounts that they have a new email.

Call Minder Premium 5 custom (5 Mailboxes)
Call Minder Premier extends the features of Call Minder and Call Minder Extra to include separate greetings making it clear you are on another call, away for some time or just unable to answer at that time.
This service will also store fax messages and allow you to call in from a fax enabled line and remotely download fax messages.
It also comes with a total of 5 mailboxes associated with the fixed line and this can be expanded to 9 mailboxes. You can also configure the Call Minder message waiting option to send a message-waiting alert to another line upon message deposit.
Linking Call Minder standard service to a mobile, with the Text Alert feature   allows you to link your mobile phone to the call minder service. A text message will be sent to your mobile whenever a new message is left on your land line. You can then call in to your land line number to listen to the message using the linked mobile.

Call Sign
Call Sign allows you to distinguish between incoming calls on the same line. You are provided with an alternate number to your existing telephone number. When somebody dials your alternate number, the telephone on that line will ring with a different ring tone. You can thus determine whom the call is for, or who the caller is, before answering the phone.

Call Waiting
With Call Waiting, a gentle beep will let you know another call is coming in. You can finish your original call, swap between calls or continue with the current call. In the latter case, the caller will be advised to call back later.

Call Waiting with Call Hold
Keep up to four calls waiting. Call hold allows you to switch calls and the original call is placed on hold.

A telecommunications company such as BT, Cable & Wireless, etc. that physically installs telephone cabling.

CDMA (Code-Division Multiple Access)
CDMA refers to any of several protocols used in second-generation (2G) and third-generation (3G) wireless communications.

Connected line Identity presentation (COLP)
Display the telephone number that your call has been connected to.

Customer Controlled Call Forwarding
Customer Controlled Call Forwarding diverts calls to all numbers to a single number of your choosing. This call-forwarding option is applied by you by programming your equipment to divert the calls. This means it is exchange-independent. Contact your equipment manufacturers if you are unsure whether your equipment supports the service.

Direct Dialling In (DDI)
A feature of ISDN2 (System) and ISDN30 lines. Typically used to provide direct dial numbers for extension users, fax machines, departments or groups of extensions. A business may have 10 lines and 100 telephone numbers. The dialled number is passed to the telephone system that routes the call to the intended recipient. As a result fewer lines need to be rented overall to provide the same level of service.

EDGE (Enhanced Data GSM Environment)
EDGE is a faster version the Global System for Mobile (GSM) wireless service designed to deliver data at rates up to 384 Kbps and enable the delivery of multimedia and other broadband applications to mobile phone and computer users.

Ethernet First Mile (EFM)
Ethernet in the First Mile (EFM) is the nickname of IEEE Std 802.3ah-2004, an amendment to the Ethernet standard, specifying Media Access Control Parameters, Physical Layers, and Management Parameters for Subscriber Access Networks . The EFM standard was approved by the IEEE Standards Board in June 2004, and officially published on 7 September 2004.
The Last Mile is the name traditionally given to the part of a public communication network that links the last provider-owned node (the central office, the street cabinet or pole) with the customer's (Premise) equipment (CPE). The First Mile is the exact same thing, viewed from the customer's perspective.
EFM does not improve or replace the existing Ethernet. It is a set of additional specifications, allowing users to run the Ethernet protocol over previously unsupported media, such as single pairs of telephone wiring and single strands of single-mode fibre (SMF). This makes the EFM port types suited for use in subscriber access networks, i.e. the networks that connect subscribers to their service provider. In essence it gives better speeds cheaply.

FTTC (Fibre to the Cabinet)
This is a telecommunication architecture based on Fibre-optic cables running to your local telephone exchange cabinet (green box on street) instead of using traditional coaxial cable or twisted pair wiring.
FTTC allows the delivery of broadband services such as high speed Internet. Maximum speeds achievable  are 80Mbps download and 20 Mbps upload.

FTTP (Fibre to the Premises)  
This is a telecommunication architecture based on Fibre-optic cables running to your property instead of using traditional coaxial cable or twisted pair wiring.  
FTTP allows the delivery of broadband services such as high speed Internet. Maximum speeds achievable are 330Mbps download and 30 Mbps upload.

GEA (Generic Ethernet Access)
Generic Ethernet Access (GEA) uses FTTC and FTTP (see above) technologies to provide non-contended Internet access.  Typical maximum speeds are 20Mbps upload and download.

GFast uses FTTC technology (see above) with an adapter on the local cabinet to increase speeds and reliability. Maximum speeds achievable are 300Mbps download and 50 Mbps upload.

GPRS (General Packet Radio Services)
GPRS is a packet-based wireless communication service that promises data rates from 56 up to 114 Kbps and continuous connection to the Internet for mobile phone and computer users.

GSM (Global System for Mobile communication)
GSM is a digital mobile telephony system that is widely used in Europe and other parts of the world.

HSCSD (High-Speed Circuit-Switched Data)
HSCSD is circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the Global System for Mobile (GSM) communication standard in 1999.

Incoming Calls Barred (ICB)
Enables you to have outgoing-only lines. All incoming calls are barred.

ISDN (Integrated Services for Digital Network)
ISDN is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.

ISDN2 or 2e
See ISDN above. This allows for 2 channels (simultaneous calls).

This is the big brother of ISDN2 and will normally have a minimum of 8 channels and a maximum of 30 (simultaneous calls).

Leased Lines
A permanent and dedicated telephone connection between two points set up by a telecommunications common carrier. Typically, leased lines are used by businesses that require a high quality, high speed Internet connection or to connect geographically distant offices. Unlike normal dial-up connections, a leased line is always active. The fee for the connection is a fixed monthly rate. Maximum speeds achievable  are up to 2Gbps upload and download.

Local Loop Unbundling (LLU)
Not actually a type of technology, but rather describes the de-regulation of the former BT exchange network, meaning third-party access to copper wiring that connects the exchange to a broadband user's property.

LTE (Long Term Evolution)
LTE is the guideline followed to achieve 4G speeds. Since 4G protocol speeds being unreachable the regulating body decided that LTE, the name given to the technology used in pursuit of those standards, could be labeled as 4G if it provided a substantial improvement over the 3G technology.

MMS (Multimedia Messaging Service)
MMS extends text messaging to include longer text, graphics, photos, audio clips, video clips, or any combination of the above, within certain size limits.

Multiple Subscriber Numbering (MSN)
Available for groups of size between 2 and 10 numbers, this is an optional feature of ISDN2 (Standard) lines allowing up to 10 telephone numbers to be assigned to a single line so that devices connected to that line can be called individually. Can be used to produce a limited version of DDI.

A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. Also known to as a PABX - private automatic branch exchange.

Permanent Outgoing Calls Barred (OCB)
Enables you to have incoming-only lines. No calls can be made from lines with Permanent OCB.

Plain Old Telephone Service (POTS)
Plain old telephone service (POTS) is the analog telephone service that was common before the advent of advanced forms of telephony such as Integrated Services Digital Network (ISDN), cellular telephone systems, and voice over Internet Protocol (VoIP).

Presentation Number
Display a different number (0845 etc) to people you call.

PSTN (public switched telephone network)
See POTS above.

Reminder Call
This service allows you to set a ‘reminder call' for a given time of day. There are two versions available. You can set up a one-off reminder call, or if you are on a system X exchange, you can set up regular reminder calls using the 24 hour clock.
At the specified time, the phone will ring and an announcement will be played.

Ring Back
This service allows you to request a ring back if the number is engaged. The engaged number will then be monitored by the network for up to 45 minutes until the line becomes available. When it does, your phone will ring with a special distinctive ringing tone - just pick it up and you will be connected. If the Ring Back service is not available, you will be played a message advising this.

SDSL (Symmetric Digital Subscriber Line)
This technology allows more data to be sent over existing copper telephone lines. SDSL supports data rates up to 3 Mbps.

Selective Outgoing Calls Barred
Enables you to bar certain categories of outgoing calls. These categories are:

  • All Calls (except 999 and 150, 151, 152, 154 and 0800)*
  • International and Premium Rate Services
  • All Operator Calls (except 999 and 150, 151, 152, 154 and 0800)*
  • National, International and Premium Rate Calls (except 999 and 144, 150, 151, 152, 154 and 0800)*
  • International, Operator and Premium Rate Services

* Indirect Access codes are not excluded from the calls barred in this option, therefore calls prefixed with an indirect access code will not connect.

Session Initiation Protocol (SIP)
SIP is the Session Initiation Protocol and includes all of the details needed to get two telephones talking.

SIM card (Subscriber Identity Module)
A SIM card is a smart card that stores data for mobile phone users. Such data includes user identity, location and phone number, network authorisation data, personal security keys, contact lists and stored text messages.

SMS (Short Message Service)
SMS is a text messaging service component of phone, Web, or mobile communication systems.

Computer software or a mobile App that enables your computer or mobile to connect to a VoIP network so it can make and receive calls.

Sub Addressing
Send up to 20 alphanumeric digits with the digits of the dialled number

System X
System X was the first national digital telephone exchange system in the United Kingdom. It is in the process of being replaced by BT's 21st Century Network (21CN).

Three-Way Calling
This service allows subscribers to speak to two or more people at the same time even if one of them is abroad. This allows a ‘conference' to take place between all parties.

UMTS (Universal Mobile Telecommunications Service)
UTMS is a third-generation (3G) broadband, packet-based transmission of text, digitised voice, video, and multimedia at data rates up to 2 megabits per second (Mbps).

VoIP (Voice over Internet Protocol)
Voice over Internet Protocol. A system that uses the internet to transmit telephone calls.