PS Engineering PMA8000 Installation Manual - Manual (Page 10)

PS Engineering
PMA8000 Series Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-890-0000 Page 2-3 Revsion 10, September 2005
NOTE:
Adding a high-performance audio control system, particularly in conjunction with high-performance active
noise canceling headsets, cannot improve on older avionics that were designed for cabin-speaker use. PS
Engineering makes no claim that the audio panel will provide a noise-free audio quality under all installa-
tion conditions, particularly with older avionics.
2.4.2 Existing GMA340 Installation
If the installation replaces a GMA340, no changes are required except to incorporate the new capabilities
of the PMA8000.
2.4.3 Power
The PMA8000-Series are compatible with both 14 and 28 Volt DC systems. A five (5) Amp circuit breaker
is required for all installations. Power and ground wires should be #22 connected to J2 Pins 8 and 9. Con-
nect airframe ground to J2 Pin 10 and 11 only. No dropping resistors are required.
2.4.4 Communications Push-to-Talk
An important part of the installation is the PTT (Push-To-Talk) switches that allow the use of your aircraft
communications radio for transmissions. There are three typical configurations that can be used. Select the
case that best fits the installation. Only the person who presses their PTT switch will be heard over the ra-
dio. If the pilot and copilot both use the PTT, the only pilot position has access to the radio. The pilot posi-
tion will have PTT control regardless of the mic selector switch or copilot PTT when the PMA8000 is in
the
OFF /E MG mode.
CASE I: PTT is built into both pilot and copilot yokes.
CASE II: PTT is in pilot yoke only. This configuration requires a modified external PTT switch plugged
into the copilot's microphone jack. (See Appendix A). When the copilot's PTT is pressed, the intercom
switches the microphone audio from pilot to copilot mic.
CASE III: No built in PTT. This requires two built in PTTs to be installed, or modified external PTT
switches to be used. Modify external PTT as required. See Appendix A.
2.4.5 Audio Panel interface
The PMA8000 is designed to interface with standard aircraft avionics, and presents a 500 Ω receiver im-
pedance. For best results, a twisted-shielded cable is recommended from the avionics audio source to the
audio panel, with the shield grounded at the audio panel 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 panel to the radio ground, using one conduc-
tor of the twisted-shielded cable.
2.4.5.1 Speaker Load
The PMA8000 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 PMA8000 ( J1 27 WRT
28). The speaker load is 16
Ω, 3W.
2.4.6 TEL (Duplex) Function for Cell Phones
This mode is designed to operate with telecommunications systems, such as the AirCell Guardian 1000.
Audio streams selected by the intercom mode are provided to the Tel output, and audio from Tel is pre-
sented to the headset. This allows a telephone-like audio interface.
The TEL mode in the PMA8000 is also compatible with many cellular telephones with hands-free headset
interfaces. A 1/8” or 3/32” jack can be installed on the aircraft panel, and interfaces with the PMA8000 as
shown: A patch cord (3/32” to 3/32”) is available from PS Engineering under P/N 425-006-7026.