ITU-T G.961 PDF

This Recommendation covers the characteristics and parameters of a digital transmission system at the network side of the NT1 to form part of the access digital section for the ISDN basic rate access. The specification of transmission system characteristics at the network side of the NT1 does not correspond to a reference point defined in the reference configuration for ISDN user-network interfaces in Recommendation I.411.

The system will support the

– full duplex;

– bit sequence independent

transmission of two B-channels and one D-channel as defined in Recommendation I.412 and the supplementary functions of the access digital section defined in Recommendation I.603 for operation and maintenance.

This Recommendation describes 4 transmission systems using different line codes and transmission methods. They are given in Appendices I to IV as examples following the understanding that only one system should be recommended and provided in an annex to this Recommendation when this is achieved in future.

NOTE – The main aspects which have made it impossible to achieve this objective are for example:

– local line electrical conditions;

– maintenance requirements and line testing;

– EMC requirements;

– safety and protection requirements;

– local network evolution aspects.

The individual appendices to this Recommendation distinguish core specifications from extension specifications. The extension specifications are given in an annex to the relevant appendix.

The core specifications consist of those aspects which are expected to be common to all applications using a particular type of transmission technique. They correspond to the functions usually provided within typical VLSI transceiver integrated circuits or are associated with the transmission characteristics at the 2-wire port.

The extension functions generally correspond to NT/LT functions which are in some cases provided external to the transceiver integrated circuits. Where a definition of an extension function is provided and the application is specified in the relevant annex it is strongly recommended that the application is not changed unless there is a need to change the definition of the function itself.

The terminology used in this Recommendation is contained in Recommendations I.112 and G.701.