PS Engineering PMA6000M-C Installation Manual - Manual (Page 12)

PS Engineering
PMA6000 Series Audio Selector Panel and Intercom System
Installation Manual
200-066-0100 Page 2-5 Rev. 1, March 2005
2.4.9 Speaker Loads
Certain VHF Nav/Comms, such as King KX170-series have internal speaker amplifiers. These are not used
with a PMA6000, but must be loaded to prevent unit failure. Connect the speaker output from the
Nav/Com to the appropriate load on the PMA6000 (bottom connector 19 and L for COM 1, etc).
2.4.10 PA Mute
Bottom connector pin 18 is a TTL logic output that is pulled low during PTT operation. This serves as an
input to external public address system to prevent feedback during transmissions.
2.4.11 Middle Marker Sense
The MM Sense output is connected to certain specific autopilots, and goes high only when a middle marker
signal is received, not in test.
2.4.12 Unswitched Inputs
The PMA6000 has two unswitched inputs. Bottom connector pin 17 is unswitched, but muted by transmis-
sions. This signal can be used for less critical inputs such as airborne telephone ringer.
Bottom connector pin T is an unswitched and unmuted audio input. This audio is always presented to the
headphones and speaker, regardless of the audio panel audio selections. This input can be use for critical
warnings, such as radio altimeter warnings.
2.4.13 Intercom
The top connector is for the intercom function. 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 Engi-
neering, Inc. Simply call the factory and obtain a wire harness work sheet. The harness will be made to
your specifications and fully functionally tested. All hardware is included. (See Appendix C for intercom
connection diagrams).
2.4.13.1 Push-to-talk intercom
PMA6000-series units with intercom board (second series of numbers on data plate) serial number above a
“G” series in stereo, or “MO series in mono, 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 relying on voice-activation (VOX).
To operate the PTT, simply rotate the PMA6000 squelch control to maximum (fully CW). Grounding the
appropriate pin on the top connector through a momentary switch will open only that intercom channel.
The pilot and copilot are individually controlled (Top connector, pins 22 and 21, respectively). All passen-
ger mics are controlled with pin 20.
This applies ONLY to units with applicable serial numbers. If a unit with serial number below that indi-
cated is installed in a position wired for the PTT, no damage will occur, only the ICS PTT function will not
function.
2.4.14 Digital recorder (-IRS units only)
If the PMA6000-series unit is identified with Option 1, 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).
To use this function, a normally-open momentary switch is installed between the top connector Pin 19 and
aircraft ground. A low-current switch is recommended.