AT&T 3.0 manual Checking Unit Loads, Unit Loads for Hybrid/PBX Mode

Unit Loads

Unit Loads

A unit load is a measure of power (1.9 watts) that you use to determine the electrical load that the components listed below place on the control unit’s power supply.

■Telephones and adjuncts

■800 DID modules

Only the telephones and adjuncts that connect to the analog and digital extension jacks (ports) on the control unit require unil load calculation, When calculating unit load, do not include any equipment with its own power supply.

Checking Unit Loads

In the event of maintenance or equipment changes, recalculate the unit loads for each carrier where there is a new configuration. Use the worksheet in Appendix B, “Unit Load Calculation Worksheet.”

As a general rule, if you can distribute the 800 DID modules and telephone modules equally across the carriers, you prevent unnecessary drain on any one carrier. However, the rule varies depending on the system’s mode. The next two sections provide the rules for calculating unit loads in various modes.

Unit Loads for Hybrid/PBX Mode

The power supply (model 391A1) generally supports six modules of any type in Hybrid/PBX mode, without requiring an auxiliary power unit. If the following conditions are true, however, 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.

The carrier has a total of more than 45 MLX-20L telephones or 34-button analog multiline telephones installed.

2-16Installing the Control Unit