Calculating Unit Loads; Unit Load Worksheet - AT&T MERLIN LEGEND Release 3.1 System Planning Manual

Unit Load Calculation
Unit Loads for the Hybrid/PBX Mode
The 391A1 and 391A2 power supplies have a maximum rating of 54 unit loads
and generally can support six modules of any type in a system in Hybrid/PBX
mode without exceeding the 54-unit maximum. If, however, both of the following
conditions are true, the unit loads on a carrier can exceed the 54-unit maximum:
All six carrier slots are occupied by MLX or analog multiline telephone
modules
The carrier has a total of more than 45 MLX-20L telephones or 34-button
analog multiline telephones installed
The 391A3 power supply has a maximum rating of 75 unit loads. If your system
contains a 391A1 or 391A2 power supply module, and the unit loads for that
carrier will exceed 54, a 391A3 power supply should be installed in the system.
Auxiliary Power Units cannot be used with the 391A3 power supply.
Unit Loads for Key or Behind Switch Mode
In a Key or Behind Switch system with four or fewer modules, no calculation is
needed. The power supply generally supports four modules of any type in Key or
Behind Switch mode.

Calculating Unit Loads

Use the worksheet and instructions in the remainder of this appendix to calculate
unit loads for each carrier. Make a copy of all pages of the worksheet for each
carrier.

Unit Load Worksheet

1. Number of modules in carrier (excluding power
supply and processor):__________________
2. Key or Behind Switch mode only:
Indicate configuration of lines; then go to Step 5.
3. Hybrid/PBX mode only:
Do all modules in the carrier have MLX and/or
analog multiline telephone jacks?
F–2
System Planning
If fewer than 5, no further calculation is required.
If 5 or 6, continue to Step 2.
If no, no further calculation is required.
If yes, continue to Step 4.
Key
Modified
Yes
No