X.51 1988 I 15 11? None Fundamental parameters of a multiplexing scheme for the international interface between synchronous data networks using 10-bit envelope structure X.51bis 1988 I 15 11? None Fundamental parameters of a 48-kbit/s user data signalling rate transmission scheme for the international interface between synchronous data networks using 10-bit envelope structure X.52 1988 I 15 11? None Method of encoding anisochronous signals into a synchronous user bearer X.53 1993 I 15 11? None Numbering of channels on international multiplex links at 64 kbit/s X.54 1988 I 15 11? None Allocation of channels on international multiplex links at 64 kbit/s 1988 I 15 11? None Interface between synchronous data networks using a 6 + 2 X.55 envelope structure and single channel per carrier (SCPC) satellite channels X.56 1988 I 15 11? None Interface between synchronous data networks an 8 + 2 envelope structure and single channel per carrier (SCPC) satellite channels X.57 1988 I 15 11? None Method of transmitting a single lower speed data channel on a 64 kbit/s data stream X.58 1988 I 15 11? None Fundamental parameters of a multiplexing scheme for the international interface between synchronous non-switched data networks using no envelope structure X.60 1988 I 13 20? None Common channel signalling for circuit switched data applications X.61 Withdrawn None Signalling System No. 7 - Data user part X.70 1988 I 13 20? None Terminal and transit control signalling system for start-stop services on international circuits between anisochronous data networks
X.51 Fundamental parameters of a multiplexing scheme for the international interface between synchronous data networks using 10-bit envelope structure 1988 I 15 11? None X.51bis Fundamental parameters of a 48-kbit/s user data signalling rate transmission scheme for the international interface between synchronous data networks using 10-bit envelope structure 1988 I 15 11? None X.52 Method of encoding anisochronous signals into a synchronous user bearer 1988 I 15 11? None X.53 Numbering of channels on international multiplex links at 64 kbit/s 1993 I 15 11? None X.54 Allocation of channels on international multiplex links at 64 kbit/s 1988 I 15 11? None X.55 Interface between synchronous data networks using a 6 + 2 envelope structure and single channel per carrier (SCPC) satellite channels 1988 I 15 11? None X.56 Interface between synchronous data networks an 8 + 2 envelope structure and single channel per carrier (SCPC) satellite channels 1988 I 15 11? None X.57 Method of transmitting a single lower speed data channel on a 64 kbit/s data stream 1988 I 15 11? None X.58 Fundamental parameters of a multiplexing scheme for the international interface between synchronous non-switched data networks using no envelope structure 1988 I 15 11? None X.60 Common channel signalling for circuit switched data applications 1988 I 13 20? None X.61 Signalling System No. 7 - Data user part Withdrawn None X.70 Terminal and transit control signalling system for start-stop services on international circuits between anisochronous data networks 1988 I 13 20? None