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Installing the Control Unit
Unit Loads
A unit load is a measure of power (1.9 watts) used to determine the electrical
load that the following components have on each carrier’s power supply:
■ telephones and adjuncts
Only the telephones and adjuncts that connect to the analog and
digital ports on the control unit require unit load calculation. Do not
include any equipment with its own power supply in the unit load
calculation.
■ 800 DID modules
Checking Unit Loads
In the event of maintenance or equipment changes, recalculate the unit loads
for each carrier resulting in a different configuration.
Use the worksheet in Appendix B.
General Rule: If you can distribute the 800 DID modules and telephone
modules equally
any one carrier.
Also, depending
provide the rules
Unit Loads for
across the carriers, you will prevent unnecessary drain on
on the system’s mode, the rules vary. The next two sections
for calculating unit loads in various modes.
the Hvbrid/PBX Mode
The power supply (model 391A1) generally supports six modules of any type
in a Hybrid/PBX system—
without requiring an auxiliary power unit.
If, however, both of the following conditions are true, the unit loads on a
carrier can exceed the 54-unit maximum, and therefore require auxiliary
power:
■
all six carrier slots are occupied by MLX telephone or analog multiline
telephone modules
2-18 Unit Loads