PS Engineering
PAC45J Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-045-2000
Page 2-3
November 2020
frame that are detected by the audio system. Follow the wiring diagram very carefully to help ensure a min-
imum of ground loop potential. Use only Mil Spec shielded wires (MIL-C-275000, or better). Under no
circumstances, combine a microphone and headphone wiring into the same shielded bundle. Always use a 2-
or 3-conductor, shield wire as shown on the installation-wiring diagram.
The shields can be daisy-chained together, and then connected to the ground.
Radiated signals can be a factor when low-level microphone signals are "bundled" with current carrying
power wires. Keep these cables physically separated. It is very important that you use insulated washers to
isolate the ground return path from the airframe to
all
headphone and microphone jacks.
2.4.2
Power
The PAC45J is compatible with 28 Volt DC systems. A five (5) Amp circuit breaker is required for all
installations. Power and ground wires should be #22AWG connect power to P451 Pin 42. Connect airframe
ground to P451 Pin 20 and 21 only.
Power consumption is as follows:
At 28V:
•
Control head Only: 400 mA
•
Hub Only: 750 mA
•
Alert audio power: 20mA
At minimum input voltage (20V):
•
Control head: 600mA
•
Hub Only: 950mA
Lighting input: <5mA
CAUTION: Do not connect or disconnect (
HOT SWAP
) any components with power applied, this may
damage the units
2.4.2.1
Alert power, P451 Pin 41,
The PAC45J has an independent alert system with the ability to play alerts even when the audio controller is
powered off. To take full advantage of this isolation a separate one (1) Amp circuit breaker is required. Power
should be #22AWG connect power to P451 Pin 41.
When power to P451-42 is present, the message will play three times or until the remote acknowledge is
selected.
2.4.2.2
Failsafe Power P451 Pin 62 and O
2
Enable P453 Pin 26
When connected to the aircraft bus, it allows for the use of Oxygen microphones in failsafe, when the O
2
microphone discrete, J453 Pin 26 is grounded.
2.4.3
Audio controller interface
The PAC45J is designed to interface with standard aircraft avionics and presents a 510
receiver impedance.
For best results, a twisted-shielded cable is recommended from the avionics audio source to the audio con-
troller, with the shield grounded at the audio controller end.
Some avionics do not provide a separate audio low and may introduce additional electrical noise into the
system. For best results, connect the audio low from the audio controller to the radio ground, using one
conductor of the twisted-shielded cable.
2.4.3.1
Front Panel Nomenclature and Audio Inputs
Due to the PAC45J flexibility with label nomenclature (custom labels) the naming of the inputs and respec-
tive control locations can change. See Appendix B – Radio Interconnect Wiring, and §2.8, Pin Assignments
for the Switch Positions associated with the respective inputs.