Ransmit Nterlock; Acklighting; Unswitched Inputs - PS Engineering PMA8000C Installation And Operator's Manual

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 lighting system to work.
If no connection to the dimmer is made, or the dimmer voltage is < .5 VDC, the white text backlighting will
be at a minimum level.
The photocell mounted in the unit face will automatically adjust the intensity of the green push-button an-
nunciator 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, in the
right ear. Unswitched 3 and 4 inputs are always presented to the crew headphones and over the aircraft
speaker.
Unswitched
Input
1
2
3
4
5 (jack)
Table 2-2 Unswitched input table
Unswitched #2, J1 pin 44 is unswitched is always connected to the Pilot's headphone. However, this
unswitched 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. In serial number DC1186 and
above, Unswitched #1 is in the right ear.
Inputs 1, 2 and 4 are fixed (1:1), and any audio level adjustments must be made at the input source.
Unswitched #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.
200-890-0303
PS Engineering
PMA8000C Audio Selector Panel and Intercom System
Installation and Operator's Manual
Hear in Hear in
Fail Safe Crew Headset
Yes Yes
No Yes
No Yes
No Yes
No Yes
NOTE
Page 2-4
SPR button Gain
Select
No 1:1(fixed)
Yes 1:1(fixed)
No Adjustable
No 1:1(fixed)
No 1:1(fixed)
Rev. 5, May 2015