PS Engineering PMA4000 Installation Manual - Manual (Page 10)

PS Engineering
PMA4000 Series Audio Selector Panel and Intercom System
Installation Manual
200-041-0002 Page 2-4 Rev 5, March 2007
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 mic 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).
2.4.4 Power and 28 VDC Dropping Resistor
The PMA4000 is compatible with both 13.8 and 28 Volt DC systems. A three (3) Amp
circuit breaker is required. Power and ground wires should be at least #20AWG twisted
pair.
If installed in a 28V aircraft, a 15 Ω, 15 watt dropping resistor must be installed in the
power input.
2.4.5 Backlighting
The PMA4000 has automatic lamp dimming of the buttons controlled by a photo-resistor.
The photocell located at the center of the unit face will automatically adjust the intensity
of the push-button lamps.
2.4.6 Intercom
All mic and headphone jacks must have insulating washers, the cable must be Teflon
coated, twisted-shielded wire, and the shield must only be connected to the ground return
wire only at the intercom connector. NOTE: This harness can be custom made by PS
Engineering, Inc. Simply call the factory (1-800-ICS-AERO) and obtain a wire harness
work-sheet. Or obtain at website. The harness will be made to your specifications and
fully functionally tested. All hardware is included.
2.4.6.1 Push-to-talk intercom
PMA4000 units include a push-to-talk intercom capability. In some extremely high noise
environments, it may be desirable to have a push to talk (PTT) intercom, instead of rely-
ing on voice-activation (IntelliVox™).
To operate the PTT, simply ground P2, Pin 16 (PTT Enable) through a switch. Then,
grounding the appropriate pin on the P2 connector through a momentary switch (Pin 4 for
the pilot, Pin 17 for copilot) will open only that intercom channel. The passengers do not
have PTT capability. Their IntelliVox™ remains active when the ICS PTT enable is
grounded. If PTT is desired for the passenger position, add a momentary, normally open
(NO) switch in series with the mic audio input to P2, pin 14 and 15.
2.4.7 Digital recorder (11941 only)
If the PMA4000-series unit is a part number 11941 there is an internal recorder built into
the unit. This stores the last 60 seconds of radio traffic from the selected Com transceiver
(the one selected for transmit). Everyone who hears the radio will hear the playback, it
will be present in the speaker (if selected) and it will mute the music.