Abstract: An apparatus for providing passive bus communication in an ISDN without use of services of a central office uses an alternative error checking (CRC) technique for communication between devices on the passive bus. This alternate CRC is interpreted as an error at the central office so that local frames are discarded by the central office.

Abstract: An apparatus for providing passive bus communication in an ISDN without use of services of a central office includes a passive bus suitable for ISDN D-channel frame communication, the passive bus having an echo channel and having a plurality of terminal devices coupled to the passive bus. A receiving circuit is coupled to the passive bus for receiving D-channel frames containing a SAPI address transmitted from the terminal devices over the passive bus. A decoding circuit is coupled to the receiving circuit for decoding D-channel addresses transmitted from the terminal devices over the passive bus. The decoding circuit includes a circuit for determining if one of the D-channel frames from the terminal devices include a predetermined SAPI address. A switching circuit is coupled to and responsive to the decoding circuit, and implements a logical communication channel between two or more of the plurality of terminal devices when the D-channel frame includes the predetermined SAPI address.