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Common Channel Signaling, A form of out-of-band signaling used on digital trunks. One time-slot (the "common channel") is used to convey signaling information. An example of a CCS implementation is the D channel of ISDN or the CCITT number 7 protocol which is used in CO to CO communication on DS-1 level trunks. The full band-width of the common channel is available for signaling, framing is accomplished by other means, generally by a bit pattern appended to each frame following the set of time-slot samples.