 from many remote terminals or computers, including functions such as message switching. Also called a communications processor. communications satellite A satellite designed to act as a telecommunications radio relay and usually positioned in geosynchronous orbit 23,000 miles (35,800 km) above the equator SO that it appears from earth to be stationary. compander A compressor at one point in a communications path for reducing the volume range of signals, followed by an expander at another point for restoring the original volume range. A compander is designed to improve the ratio of the signal to the interference entering in the path between the compressor and expander. compression The application of any of several techniques to reduce the number of bits required to represent information in data transmission or storage, thereby conserving bandwidth and/or memory. compressor An electronic device that compresses the volume range of a signal. concatenation (1) The linking of transmission channels (e.g., phone lines, coaxial cable, optical fiber) end to end. (2) The linking of SONET STS-1 frames in order to carry a broadband information stream. concentrator A device that connects a number of circuits that are not all used at once to a smaller group of circuits for economical transmission. A telephone concentrator achieves the reduction with a circuit-switching mechanism. In data communications, a multiport repeater hub brings together the connections from multiple network nodes. Concentrators have moved past their origins as wire concentration centers and often include bridging, routing, and manage- ment devices. conditioning A procedure for making transmission impairments of a circuit lie within cer- tain specified limits, typically used on telephone lines leased for data transmission to improve the possible transmission speed. Two types are used: C conditioning and D conditioning. Also called line conditioning. configuration The devices and programs that make up a system, subsystem, or network. The term configuratio