LA Audio PC90 - Manual (Page 6)

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Cable Testing.
The PC90 is designed to be a
polarity tester for electronic
audio systems, not specifically
a cable tester.
If a false reading is found in
a system and a cable fault is suspected then ideally a dedicated cable tester
should be used to trace the fault. However, if you want to check an individual
XLR cable and the PC90 is what you have at hand:
• Set the 'Hot Pin' switch on both units to Pin  and select 'LINE' as the input
on the Receiver.
then,
• Set the 'Hot Pin' switch on both units to Pin .
If the cable is correct the green ‘IN’ LED will flash in both cases, if the cable is
reversed it will show nothing, thus indicating a fault condition.
Note: The Emitter’s level control should be set to about  o'clock for this test.
Application Notes.
There are various applications for the PC90. Below are a few suggestions about
how to get the best from your PC90.
• Feed the signal from the emitter into a PA system and place the receiver in
front of each loudspeaker in turn to ensure that the system is in-phase.
• For a multi-mic application, connect the receiver to a mixing console
output and feed each microphone with the generated pulse. The receiver
may then be used to check that all the mics are in phase, (if out of phase,
cancellation effects may occur where mics are close together).
• The system may be used for checking phase transmission on tape
recorders, (be prepared for some surprises!). This test can be made by
recording the generated signal onto tape and connecting the receiver to
the machine's output. This is really useful in the recording studio, when
using effects off tape which are combined and for checking tape machine
wiring.
• The system may also be used to check telephone lines, satellite links etc.
Keep in mind that some crossover networks and speaker systems
deliberately place certain speakers out of phase for correct operation.
Check the technical specifications of the system before making any polarity
adjustments.