CCITT Recommendation R.115 (11/1988) – MAINTENANCE LOOPS FOR TDM-SYSTEMS
2 Location of the loops
3 Names, types and definitions of the loops
3.1 Loop a - digital multiplexer aggregate loop
3.2 Loop b - analogue aggregate modem loop
3.3 Loop c - analogue line loop
3.4 Loop d - digital aggregate modem loop
3.5 Loop f - tributary analogue loop
3.6 Loop g - tributary digital loop towards the Muldex
3.7 Loop h - tributary digital loop towards the tributary interface unit
4 Use of the loops
5 Methods of control
6 Control signalling
6.1 Alternative A
6.2 Alternative B
6.3 Maintenance channel signalling
7 Routing of the maintenance control signals
8 Application
9 Use of the maintenance channel