AT&T MERLIN LEGEND Communications System Release 2.0 Maintenance And Troubleshooting Manual page 202

Unit Load Calculation Worksheet
9.
Try to exchange modules between carriers to reduce the unit loads for slots 5
and 6 through 27. (Remember that the 100D, 400, 400 GS/LS/TTR, 800, and
800 GS/LS modules have unit loads of 0.0. ) Repeat Steps 1 through 8 to
recalculate unit loads for new configuration.
If the exchange reduces the unit load for slots 5 and 6 through 27 or less,
auxiliary power is sufficient.
If the exchange does not reduce the unit load for slots 5 and 6 through 27,
install wall power units for the appropriate number of telephones to reduce the
unit load to 27.
NOTE:
Empty slots are not permitted between modules.
Unit Load Worksheet B-9