电信专业英英词典C-7（在线收听）

　　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 network transmission 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 carrier networks. 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 mutual interference. 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