common channeling signalling system no. 7 (CCS7)
Signaling system No. 7 (CCS7) is a central channel signaling system in digital networks and was defined primarily for ISDN. This signaling system is not bound to the transmission channels of the user information.
Central channel signaling differs from channel-bound signaling methods in that the control information is transmitted separately from the 64 kbit/s user channels in special "central" 64 kbit/s signaling channels shared by many user channels.
This signaling takes place between the ISDN exchanges and is therefore also called inter-office signaling. Signaling via the signaling channel regulates the exchange of control information between the ISDN exchanges that is required to establish and terminate connections and to provide various service features. The signaling system No. 7 is optimized for 64 kbit/s transmission rate, but can also be used with other speeds.
The CCS7 is an ANSI standard as SS7 and a CCITT standard as SS7.