PS Engineering
PAC45T Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-045-5100
Page 2-4
Rev. 2, Jan. 2019
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 will
damage the units
2.4.2.1
Alert power, P451 Pin 41,
The PAC45T 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 P451-41 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 PAC45T is designed to interface with standard aircraft avionics, and presents a 510
receiver imped-
ance. For best results, a twisted-shielded cable is recommended from the avionics audio source to the audio
controller, 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.
2.4.4
Backlighting
Control of the unit backlighting is through the aircraft avionics dimmer, each control head is independent.
Connect P455 Pin 6 to the aircraft dimmer bus. The ratio of white to green indicator intensity is adjustable,
see
The dimmer voltage can be configured in the field.
2.4.5
Unswitched inputs
These inputs are presented to the pilot and copilot regardless of the audio configuration, and will always mute
the crew entertainment inputs. These 510 Ω inputs can be used for altimeter DH audio, TAWS audio, TCAS
audio, or any other critical audio signal.
Unswitched #1 is always presented to the crew headphones, and is available to the pilot in fail-safe (off)
mode.
Unswitched
Input
Input Pins
Pilot Hear in
Fail Safe
Hear in
Crew Headset
1
P452 - 55
WRT
15
Yes
Yes
2
P452 - 35
WRT
16
No
Yes
3
P452 - 56
WRT
17
No
Yes
4
P452 - 36
WRT
18
No
Yes
Table 2-2 Unswitched inputs
2.4.6
Cockpit Voice Recorder
The PAC45T audio controller contains a Cockpit Voice Recorder output for the pilot and copilot.
Pilot CVR output is P454-62; Copilot CVR output is P454-61 both with respect to CVR low, P454 19
The CVR output is consistent with RTCA DO-214A §1.5.7,