PS Engineering PMA8000C Installation Manual - Manual (Page 11)

PS Engineering
PMA8000C Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-890-0303 Page 2-4 Rev. 3, May 2014
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 panel to the radio ground, using one conduc-
tor of the twisted-shielded cable.
2.4.5.1 Speaker Load
The PMA8000C contains one speaker amplifier. Some units with internal speaker amplifiers, such as the
King Radio KX170-series, require a resistive load to prevent damage if their speaker amplifier is not used.
Connect the speaker output from the unit to the COM 2 Speaker load input on the PMA8000C (J1 27 WRT
28). The speaker load is 16
, 3W. Only one speaker per load is available in the PMA8000C.
2.4.6 Transmit Interlock
Some communications transceivers use a transmit-interlock system. To fully utilize the Split Mode feature,
this function must be disabled. Consult that manufacturer's installation manual.
2.4.7 Backlighting
The PMA8000C has an automatic dimming of the pushbutton annunciation LEDs and marker lamps con-
trolled by a photocell. Control of the unit backlighting is through the aircraft avionics dimmer For 14 V
aircraft, connect J2 Pins 6 and 7 to the aircraft dimmer bus, and pin 5 to ground. For 28-volt systems, con-
nect pin 7 to the aircraft dimmer, and pins 5 and 6 to ground.
If an external dimmer control is not used, a constant back light illumination can be established for nighttime
viewing. Pin 6 or 7 (depending on system voltage) must be tied to power (J2, pin 8 or 9) for the back light-
ing system to work. The photocell mounted in the unit face will automatically adjust the intensity of the
push-button annunciator LEDs.
2.4.8 Unswitched inputs
J1, pins 31, 29 and J2 pin 15 are unswitched, unmuted (by transmitter keying), inputs # 1, 3 and 4, respec-
tively. These inputs are presented to the pilot and copilot regardless of the audio configuration, and will
always mute the entertainment inputs. These 510Ω inputs can be used for altimeter DH audio, GPS way-
point audio, autopilot disconnect tones, or any other critical audio signal. Unswitched #1 is always present-
ed to the speaker, plus to the crew headphones, and is available to the pilot in fail-safe (off) mode. Un-
switched 3 and 4 inputs are always presented to the crew headphones and to the aircraft speaker.
Unswitched
Input
Hear in
Fail Safe
Hear in
Crew Headset
SPR button
Select
Gain
1 Yes Yes No 1:1(fixed)
2 No Yes Yes 1:1(fixed)
3 No Yes No Adjustable
4 No Yes No 1:1(fixed)
5 (jack) No Yes No 1:1(fixed)
Table 2-2 Unswitched input table
Unswitched #2, J1 pin 44 is unswitched is always connected to the Pilot’s headphone. However, this un-
switched audio is only presented to the aircraft speaker when the SPR push button has been selected.
The audio low for unswitched #4 (J2, pin 15) should be connected to a convenient audio low. However, this
should NOT be connected to Music Low.
Unswitched #1 is presented to the pilot headphone in fail-safe (off) mode.
NOTE
Inputs 1, 2 and 4 are fixed (1:1), and any audio level adjustments must be made at the input source. Un-
switched #3 has a variable adjustment control located on the bottom side of the unit. This control allows
you to adjust the volume level of that unswitched input. Refer to Adjustments section.