CCITT



　　CCITT is the International Consultative Committee for Telephone and Telegraph, a consultative committee to the International Telecommunications Union (ITU) which recommend international standards for telephone and telegraph services and facilities to aid international connectivity and interoperability.



　　CCSA



　　common-control switching arrangement



　　CCS



　　centi-call seconds or common-channel signaling



　　CDMA



　　code division multiple access



　　Cell Relay



　　Call relay is the process of transferring data in the form of fixed length packets called cells. Cell relay is used in high-bandwidth, low-delay, packet-like switching and multiplexing techniques. The objective is to develop a single multiplexing/switching mechanism for dividing up usable capacity (bandwidth) in a l-manner that supports its allocation to both isochronous (e.g., voice and video traffic) as well as packet data communications services. Standards groups have debated the optimum cell size. Small cells favor low delay for isochronous applications but involve a higher header to user information overhead penalty than would be needed for most data applications. The current CCITT specification for BISDN is for a 53-byte cell which includes a 5- byte header and a 48-byte payload.



　　Centi Call Seconds (CCS)



　　CCS is a unit of the average traffic intensity of a facility during a period of time, a CCS is 100 call seconds of traffic during one hour. Therefore a single traffic source, e.g., one call that generates traffic 100% of the time produces 36 CCS of traffic per hour, i.e., 3600 seconds of traffic every 3600 seconds. An equivalent amount of traffic could also be generated by 10 sources that only generate traffic 10% of the time. That is, 10 sources of traffic generating 3.6 CCS each, contributes the same total traffic as a single 36 CCS traffic source. An alternative measure for traffic is erlangs where 1 erlang equals 36 CCS.



　　CENTRal EXchange (Centrex)



　　Centrex is a LEC-provided switching service for business customers that permits station-to-station dialing, listed directory number service, direct inward dialing and station number identification on outgoing calls. The switching functions are usually performed in a central office. Digital Centrex offers the advanced features of fourth generation PBXs, without the need to purchase or lease equipment and, in most cases, eliminates the need for floor space, electrical prime power and heating, ventilation and air conditioning.



　　Central Offices (CO)



　　A central office is a telephone company building in which network equipment such as switches are installed.



　　Channel



　　A channel is a single communications path in a transmission medium connecting two or more points in a network, each path being separated by some means; e.g., spatial or multiplex separation, such as frequency or time division multiplexing. "Channel" and "circuit" are often used interchangeably, however circuit can also describe a physical configuration of equipment that provides a networktransmission capability for multiple channels. The characteristics of channels and circuits are determined by the network equipment and media used to support them.



　　Channel Service Unit (CSU)



　　Channel Service Units (CSUs) and Data Service Units (DSUs) are required to connect digital customer premises equipment (CPE) to carriernetworks. A CSU is network channel terminating equipment (NCTE) attaching as CPE to telephone company's digital circuits, and protecting the network from harm. Other CSU functions include line conditioning and equalization, error control (e.g., bipolar signal violations), and the logical ability to respond to local and network loop back circuit testing commands. See Data Service Units (DSU).



　　Circuit Associated Signaling



　　Circuit Associated Signaling is a technique that uses the same facility path for voice and signaling traffic. Historically this approach was selected to avoid the costs of separate channels for signaling and because the amount of traffic generated by signaling is small compared to voice, minimizing the chance for mutualinterference. Circuit associated signaling can be contrasted with some common-channel signaling systems that use completely separate packet switched networks for signaling traffic.



　　Circuit Switching



　　Circuit switching is a process that establishes connections on demand and permits the exclusive use of those connections until released. Packet and message switching, primarily used in data communications networks are alternative switching techniques.



　　City Wide Digital Centrex



　　A city wide digital centrex is a capability to serve multiple business locations within a single NXX (exchange code), using multiple LEC central office Centrex switches. Outside callers are unaware that multiple business locations are involved.



　　CLEC



　　Competitive Local Exchange Carrier, most commonly referred to as Competitive Local Exchange Carrier.



　　CLLI



　　Common Language Location Identifier



　　CMIP



　　common management information protocol



　　Coaxial Cable



　　Coaxial Cable (also called coax cable or coax) consists of an insulated central conductor surrounded by a second cylindrical conductor that is clad with an insulating sheath. The outer conductor usually consists of copper tubing or copper braid.



　　COC



　　central office connections



　　Codec



　　Codec is a contraction of coder and decoder; a device that encodes analog signals into digital signals, for transmission through a network in digital format, and decodes received digital signals back into analog signals.



　　Common Channel Signaling (CCS)



　　CCS is a signaling system developed for use between stored program control digital switching systems, in which all of the signaling information for one or more trunk groups is transmitted over a dedicated signaling channel, usually, but not always completely separate from the user traffic bearing facilities.



　　Common Management Information Protocol (CMIP)



　　CMIP is the OSI protocol for network management. A structure for formatting messages and transmitting information between reporting devices (agents) and data collection programs, developed by the International Standards Organization and designated ISO/IEC 9596.



　　Communications



　　Communications is the process of representing, transferring, interpreting or processing information (data) among persons, places, or machines. Communications implies a sender, a receiver, and a transmission medium over which the information travels. The meaning assigned to the data must be recoverable without degradation.



　　Conditioning



　　Conditioning is an adjustment made to the electrical characteristics of a cable pair to improve its performance for a specific use.



　　Conductor



　　In electrical circuits, a conductor is any material that readily permits a flow of electrons (electrical current) through itself. Analogously, optical fibers are sometimes said to conduct light waves and are also referred to as conductors.



　　Corporation for Open Systems (COS)



　　COS is a nonprofit organization composed of manufacturing, service, and user organizations in the computer communications area. Seeks to facilitate the development of the international, multi-vendor marketplace through the development, introduction, and verification of OSI and ISDN standards and by ensuring vendor equipment interoperability.



　　CO



　　central office



　　CPU



　　central processing unit



　　Cross Connect



　　1.in a premises distribution system, equipment used to terminate and administer communications circuits. In a wire cross connect, jumper wires or patch cords are used to make circuit connections, between horizontal and backbone wiring segments. 2. in transmission systems a patch panel for connecting circuits.



　　CSDC



　　circuit-switched digital capability



　　CSMA/CD



　　Carrier sense multiple access with collisiondetection; a local area networkcontention based access control protocol technique by which all devices attached to the network "listen" for transmissions in progress before attempting to transmit themselves and, if two or more begin transmissionsimultaneously, are able to detect the "collision". In that case each backs off (defers) for a variable period of time (determined by a preset algorithm) before again attempting to transmit. (Defined by the IEEE 802.3 standard).



　　CSR



　　Centrex station rearrangement



　　CSU



　　channel service unit



　　Customer Premises Equipment



　　Customer Premises Equipment is all telecommunications terminal equipment located on the customer premises. except coin operated telephones.

关键字:电信专业英英词典

生词表: