PictureTel Concorde 4500 Servicing Manual page 123

4. Verify that the AC voltage from an additional AC source, used for
optional equipment, is equal to the voltage of the main AC power
source. Do this by plugging the leads from the digital voltmeter
into the system ends of the two cables in each of the following
positions:
a. Plug the voltmeter leads into the ground leads of the AC
cables. The reading should be zero.
b. Plug the voltmeter leads into the neutral lead of one AC
cable and into the ground lead of the other AC cable.
The reading should be under 1 VAC.
5. Verify that the AC phase from an additional AC source, used for
optional equipment, is equal to the phase of the main AC power
source. Do this by plugging the leads from the digital voltmeter
into the hot (powered system end) leads of the two AC cables.
The reading should be under 1 VAC; if the reading is roughly at
or above the nominal line voltage, the two sources are most
likely of a different phase.
Verifying Electrical Voltage
4-25