ITU-T M.910 PDF

General

The international leased group links in this Recommendation relate to corrected group links in the Recommendation cited in [1].

The composition of a leased group link and the terminology used for maintenance purposes is given in Recommendation M.900.

The procedure for setting up an international leased group link should as far as possible follow the principles given in Recommendation M.460 [2].

For the purpose of this Recommendation, the constitution and subsequent line-up and maintenance practice assumes that the group link between renters' premises is operated throughout in the frequency range 60-108 kHz.

Where, as in some cases, modems are fitted at the terminal national centres the group link is defined as existing between defined access points at these centres.

In such cases the terminal national section is treated for lining-up and maintenance purposes as a separate section and not part of the group link as defined in Recommendation M.900.

In some cases, where the wide-spectrum transmission equipment located at the renter's premises is not frequency band restricted, it may be found necessary to include a through-group filter at the terminal national centre in the transmitting direction of transmission, in order to prevent interference by the wide-spectrum signals into adjacent groups in the carrier systems, over which the group is routed.

Also, when measuring at the terminal national centre in the receiving direction of transmission, a through-group filter may be necessary in the measuring circuit, in order to prevent signals from adjacent groups affecting the measurement results.