AT&T MERLIN LEGEND Release 3.1 Maintenance And Troubleshooting Manual page 288

Unit Load Calculation Worksheet
7. Try to exchange modules between carriers to reduce the unit loads to
54. (Remember that the 100D, 400, 400 GS/LS/TTR, 800 GS/LS-ID, 800,
800 NI-BRI, and 800 GS/LS modules have unit loads of 0.0.) Repeat
Steps 1 through 6 to recalculate unit loads for the new configuration.
If the exchange reduces the unit load to 54 or less, any power
supply module is sufficient.
If the exchange does not reduce the unit load to 54 or less, a
391A3 power supply is needed. Continue to Step 8.
NOTE:
Empty slots are not permitted between modules.
C–6
Maintenance and Troubleshooting