Can refer to a number of different types of wires or groups of wires (conductors), capable of carrying voice and/or data that usually comprise either twisted pair or coaxial cable.
Cable entrance facility
The area in a central office where outside plant cables carrying subscriber lines  and inter-office transmission facilities enter the building.
Carrier access billing system: process for billing interexchange carriers and other service providers that for many network operators, represents a critical component of their top-line revenues in terms of recovering some of the cost of providing the local loop.
Customer access line charge:  a per-minute charge paid to local service providers by long-distance carriers that applies to every local loop according to the type of circuit (eg leased line or local access circuit) and also whether the end user is business or residential.
Call minute
The basic unit of measurement traditionally used in the provision of wholesale billing for telecoms services.
Customised applications for mobile network enhanced logic.
The volume of traffic a telecoms circuit facility is able to carry.
Customer account record exchange: ATIS industry standard for formatting the exchange of equal access/subscription information between inter-exchange carriers and telcos.
Customer account record exchange/industry standard interface
1) A private or public company that provides communications circuits.
2) A radio wave being used for the transmission of voice and data.
Carrier hotel
A building that houses many local and long distance telcos providing data/voice/video, internet access, web hosting and/or switching services. Also, know as a “co-location centre”, a carrier hotel is a secure physical site offering bulk capacity processing, handling service and where various data
communications media converge and interconnect.
Carrier-grade Ethernet
Technology developed for network operators that allows Ethernet to be transported over a network infrastructure. The five key attributes defined for carrier grade Ethernet by the Metro Ethernet Forum (MEF) are: hard QoS, reliability, scalability, service management, and TDM support. Carrier-grade Ethernet became possible once the ITU’s Draft Martini standard              untethered Ethernet from the LAN and enabled pure, end-to-end delivery of Ethernet services across the WAN. Service benefits include lower cost and higher-speed data for subscribers, while the technology itself is predicted to result huge savings in terms of opex for service providers and operators in the access/metro, WAN and long-haul sectors. For carriers, there are as many as nine different approaches to service implementation depending on the method of access (ie copper, fibre or wireless). These include: Ethernet over ATM; Ethernet over copper; Ethernet over MPLS; Ethernet over SDH/Sonet; Ethernet over WDM; native switched Ethernet; multilink point-to-point protocol (MLPPP) – also known as bonding. Emerging wireless access methods include Wifi and Wimax. The implementation approach adopted by a carrier depends largely on its legacy infrastructure.
Cascade billing model
Method of interconnect billing under which each operator in a chain pays or charges only the “downstream” or “upstream” operators respectively.
Calling card and third-party number settlement (see CMDS)
Constant bit rate: refers to delay-intensive applications such as video and voice that must be digitised and represented by a continuous, repetitive or uniform transfer of information (ie bitstream).
Completion of call to busy Subscriber/customer care and billing system
Clear channel capability (see clear channel)
Call clarity index:  ITU-T measure of telephone voice quality derived from monitoring ordinary user calls.
Common channel interoffice signalling:  the forerunner to SS7, a method of carrying telephone signalling information along a path different from that used for transmitting the voice or data traffic of the call.
Customer carrier name abbreviation: the common language code used by an interexchange carrier providing interlata facilities. This code identifies the IXC to be contacted for provisioning (see also ACNA).
Common channel signalling: a high-speed packet-switched network that is separate from the public packet-switched and message networks.
Chromatic dispersion: a physical phenomenon that occurs when each wavelength of light travels through the same material (ie an optical fibre system) at its own particular speed, causing information bits to spread along the network and degrade the quality of the transmission signal.
CDMA development group
Code division multiple access
Brand name for the north American CDMA air interface standard aimed at third-generation mobile requirements (see also 3G and IMT-2000). Considered to be a rival to UMTS – the 3G standard dominant in most markets.
Content delivery network or content distribution network: a system of computers networked together across the Internet that cooperate transparently to deliver content (especially large media content) to end users.
Call detail record: a file containing information about recent system usage.
Cellular telephone system
A high-capacity, land-based mobile (also known as wireless) telephone system that incorporates many radio base stations – or “cells” – re-using frequencies as much as possible in order to cover a defined geographic service area. Examples of this technology include GSM, cdma2000 and UMTS.
Derived from the term “central exchange”, Centrex is a class of central office service that provides the equivalent of PBX services direct from a telco’s switching system, such as call forwarding, call transfer and least cost routing.
Circuit emulation switching
Carrier facility assignment:  the identifier or location where an IXC, CAP or LEC interconnects with the incumbent carrier and allows wholesale access customers to validate the DS1/DS3 at system and channel levels.
When a subscriber changes from one network service provider to another it is known as (customer) churn and is considered as a key performance indicator          of any telecoms business with a subscriber-based service model.
Carrier identification code
Carrier identification parameter: a SS7 service that allows carriers to consolidate trunk groups by recognising traffic generated by multiple carrier identification aodes (CICs) onto a single trunk group.
Committed information rate: guaranteed bandwidth in a virtual circuit on a Frame Relay service where the customer has stipulated an average rate of information transfer.
A two-way communication path between two end points, between an end point and a network service node, or between two service nodes.
Circuit code
The specific interexchange carrier trunk group required to carry the call for SS7 messages.
Circuit emulation
A connection over a virtual, circuit-based network that provides the same service to users as delivered by a point-to-point, fixed-bandwidth circuit.
Circuit switching
Switching system on which PSTN networks are based, whereby a dedicated, physical circuit exists between sender and receiver for the duration of the call. Next-generation networks are based on shared networks that employ packet switching.
Class 4 switch
PSTN switching equipment used to interconnect Class 5 switches for high-volume traffic exchange. A Class 4 switch is generally known as a “carrier class switch” serving several service providers with call termination.
Class 5 switch
PSTN switching equipment used by operators providing voice services for supporting PBX features such as voicemail, call forwarding and redial.
Class of exchange or class of office
A ranking assigned to a switching point in the telephone network that is determined by its switching functions, inter-relationships with other exchanges, and transmission requirements.
Clear channel
A circuit that provides its full bandwidth for a user’s service because there are no framing or control bits (for signalling) required. This ability to transmit unrestricted digital information (UDI) over a channel has two benefits: it allows carriers to transmit information directly to Europe and other countries that have 64Kbps clear channel services; and also enables carriers to use aggregation of time slots to create larger pipes.   A transparent, 64Kpbs clear channel connection between mobile networks for example, allows mobile operators to offer their customers high-quality,face-to-face video calls, without the need for echo suppression or bit manipulation.
Clearing house
A company that collects and processes billing and roaming information (CDRs)   on behalf of carriers in order to facilitate settlement of inter-carrier fees.
Competitive local exchange carrier
Calling line identification
Centralised message distribution system:  the billing record and clearing house transport method used by ILECs to exchange information, such as CABS and CATS records.
Central office:  a building where subscriber lines are joined to switching equipment in order to interconnect them with other end users, both locally and via long distance carriers. This term can also apply to a building housing just a single switch (aka public exchange), or a number of switching exchanges.
Co-located inter-connection equipment
Telecoms cabling and equipment owned/leased and installed by the co-locator for their sole use.
An arrangement whereby the facilities of one party (the co-locating party) are terminated with the equipment necessary to provide interconnection or access to the network elements offered by a second party. A carrier hotel provides co-location on a massive scale, offering various services to customers ranging from modest-sized racks to dedicated rooms or operations suites. Carrier hotels may also offer hardware and software installation, maintenance and update services.
A mechanism for allocating very large amounts of bandwidth for transport of a payload associated with a “super-rate service”, which is a service at a transmission rate greater than the normal maximum rate of OC-1. At the physical layer, this means replacing multiple payload groupings to create a single communications channel by linking them together in a series or chain.
Content provider
The company that supplies the material/media (eg ringtones, news, sports and weather information) for a telecoms or internet service, rather than the network.
The condition that results when two or more independent data sources are transmitted simultaneously over a shared channel. Often described in terms of a contention ratio that indicates the degree of competition for available bandwidth that can be anticipated on the shared channel and applies specifically to the number of users connected simultaneously to an ISP and who share a fixed bandwidth. As the number of users increases, the quality of service degrades accordingly.
Core network
A combination of high-capacity switches and transmission facilities forming the backbone of the carrier’s network. End users access the core network via the edge network.
Customer premises equipment
Customer proprietary network information
Calling party pays: a system of charging for telecoms services whereby the party that initiates the call (the “calling party”) pays for both the origination and termination of the call.
Carrier pre-selection: a facility offered to customers allowing them to specify defined classes of call to be carried by an operator selected in advance (and having a contract with the customer) without having to dial a routing prefix or use a dialler box.
CDMA roaming exchange: The CDMA equivalent of a Global/GPRS roaming exchange node (see GRX).
Circuit switched data
Called subscriber identifier
Customer service record: a record containing customer-specific information including listing, billing and service and equipment sections detailing the type of listing(s) for the account, as well as a breakdown of the lines and features.
Channel service unit/data service unit
Cell transfer delay: ATM performance parameter that measures the average transit delay of cells between a source and destination over a given virtual circuit.
Coarse wavelength division multiplexing: a form of optical wavelength division multiplexing that uses wider spacing between channels in order to lower component costs.