PS Engineering PMA7000H Installation Manual - Manual (Page 12)

PS Engineering
PMA7000H Series Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-780-0429 Page 2-5 Rev. 4, Dec 2012
2.4.7 Backlighting
The PMA7000H has an automatic dimming of the pushbutton annunciator LEDs and marker lamps con-
trolled by a photocell. Control of the unit backlighting is through the aircraft avionics dimmer. Connect the
dimmer control line to J1 pin D for 14-volt systems, and to J1 pin F for 28-volt systems. Pin E is light
ground.
If an external dimmer control is not used, a constant low-level back light illumination can be established for
nighttime viewing. Pin D or F (depending on system voltage) must be tied to power (J1, pin 20) for the back
lighting 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 T, 17, U and X are unswitched, unmuted inputs. These inputs are presented to the pilot and copilot
regardless of the audio configuration, and will mute the entertainment inputs unless the PMA7000H has the
SoftMute® inhibited with the ICS button (see §3.6.3.3). These 510Ω inputs can be used for altimeter DH
audio, GPS waypoint audio, autopilot disconnect tones, or any other critical audio signal. This input is not
related to the cellular telephone interface. NOTE: These inputs are fixed (1:1), and any audio level adjust-
ments must be made at the input source.
2.4.9
PA Mute (J1, Pin 18)
Pin 18 of J1 is a TTL logic output that is pulled low during PTT operation. This serves as an input to exter-
nal public address system to prevent feedback during transmissions.
2.4.10 Public Address Function (J2, Pin 18)
By connecting the top connector (J2), Pin 18 to ground, the pilot’s microphone audio is placed on the cabin
speaker output. When the pilot’s PTT is activated, his voice is heard over the speaker. The copilot can con-
tinue to use the selected com.
We recommend installing a toggle switch to connect the cabin speaker output (pin W, bottom connector) to
a rear or public address speaker instead of the cockpit speaker close to the pilot. This will prevent feedback.
2.4.11 Control Output (J2, Pin A)
Pin A of the top connector is pulled to ground whenever the AUX button is depressed. This serves as a con-
trol line for external devices, such as a entertainment system that the pilot wishes to control.
This could be used in conjunction with a PA to control J2, Pin 18, as well as an external relay to change to
the cabin speaker from the cockpit.
This pin can also be used to control passenger Karaoke Mode, by connecting to pin V of the J2.
2.4.12 Cockpit Voice Recorder Output
Top connector (J2) Pin 20 is the pilot CVR output, and Pin 21 is the copilot CVR output (WRT Pin 22).
These contain the audio from selected radio and crew microphones, regardless of the intercom VOX or vol-
ume level. In the enhanced version, the audio contains the selected radio audio, intercom audio, and
sidetone (in transmit), and crew mic audio is derived from ICS instead of from the direct microphone pick
up.
2.4.13 Intercom wiring
The top connector (J2) is for the intercom and additional functions. See Appendix for intercom connection
configurations. It is critical to the proper operation of this system to have this connector wiring made in
accordance with these diagrams. Use 2- and 3-conductor, MIL-spec cable as shown. Connect the shields at
the audio panel end only, and tie to the audio low inputs as shown.