Nortel DMS-100 Series Maintenance Manual page 391

Run lines tests
To access subscriber lines from the LTP or the ALT level, a metallic test
access (MTA) minibar switch is used with a metallic test pair.
Up to 32 RCS modules can share a metallic test pair. A maximum of 2000
subscriber lines are recommended for support off one test pair. This
recommendation is to make sure that the system rejects the least possible
subscriber line test requests. This event occurs because another line has the
test pair in use.
The RCT, RCS, and RCS modules can share a metallic test pair. All
modules that share a test pair must be of the same type. If an RCS uses a
test pair, additional RCS modules can share the test pair. The RCT and RCS
modules cannot share the pair with the RCS modules.
The following limits apply to subscriber lines diagnostics:
LTP-level tests on special-service lines are not supported.
Only one line on an RCS can be tested at one time.
More than one RCS in a group of RCS modules at the same site, with the
same frame number can share a MTA vertical test pair. If this event
occurs, one line on that group of RCS modules can be tested at a time.
Note: The SPOTS card, S9CD271A, can be used as a special-service or
single-party plain old telephone service (POTS) card. The same
diagnostics can be run on the SPOTS card as are run on single-party
cards.
The following figure shows how MTA is used with an RCS line card:
DMS-100 Family SMS Maintenance Manual XPM10 and up
Trouble isolation and correction 9-27