AT&T Merlin 820 Service And Maintenance Manual page 31

Determine if you have an auxiliary power unit or a voice terminal power
Step 2.
supply.
IF
You have an auxiliary power unit,
You do NOT have an auxiliary
power unit,
You have a voice terminal power
supply,
You do NOT have a voice terminal
power supply,
Note: An auxiliary power unit may be required in cases where the con-
trol unit must handle extreme work loads. An extreme load may
exist when you have a combination of the following: the maximum
number of voice terminals for your system, several voice terminal
accessories, long wiring runs between the control unit and the
voice terminals, and most of the voice terminals are being used at
the same time. If the light indicators on some of the voice termi-
nals become dim or go out altogether during periods of heavy use,
it could mean that an auxiliary power unit is required for normal
operation. To determine if you need an auxiliary power unit,
disconnect your voice terminals and accessories in your system
until the number of terminals, hands-free units and headset
adapters is no more than twenty. Then perform the action that
caused the trouble. If the trouble is no longer present, you need an
auxiliary power supply.
Basic Trouble Tests
THEN
Go on to "HOW TO SELECT THE
CORRECT PROCEDURE."
See note below.
Go on to Step 3.
Go on to "HOW TO SELECT THE
CORRECT PROCEDURE."
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