PMA4000 Audio Panel

Part No: 11942

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PMA4000 Audio Panel

Panel mounted audio selector panel w/the added capability of a 4-station intercom. Provisions for switching two communications transceivers & navigation receivers, as well as providing a speaker amplifier are all part of this integrated, compact unit.


PS Engineering's exclusive IntelliVoxT with individual volume controls.


This section provides detailed operating instructions for the PS Engineering PMA4000 Audio Selector Panel/Intercom Systems. Please read it carefully before using the equipment so that you can take full advantage of its capabilities. This section is divided into three sections covering the basic operating areas of the PMA4000 systems. They are: Audio Selector, Transceiver Selection and Intercom.

Certified 4 Station Intercom

Approval Basis The PMA4000 Audio Selector Panels (P/N 11942) are FAA approved under TSO C50c (Audio Amplifiers).

Audio Selector

Audio Selector Through the use of four latched, push-button, back-lit switches, it is possible to select any or all receiver audio. When selected, an internal backlight will illuminate indicating which audio source is selected. The Com toggle switch controls what transceiver is being heard by the pilot and copilot. "C1" (Com 1) and "C2" (Com 2) push-buttons select the receiver, and are used to monitor a com that is not selected for transmit. You will always hear the audio from the transceiver that is selected by the 2-position mic selector toggle switch. The users can identify which receivers are selected by noting which push- button switches are illuminated. Push buttons labeled N1 (Nav 1), N2 (Nav 2) are "latched" type switches. When one of these buttons is pressed, it will stay in the "in" position. Press the switch again and it be in the "out" position and remove that receiver from the audio. While selected, an internal lamp will also annunciate the switch.

Intercom Mode Selector Switch

Unit power is turned on and off by the mode selector switch. In the 899 or "- " position, the pilot is connected directly to Com 1 allowing transmit and receive capability regardless of unit condition. Any time power is removed or turned 899, the audio selector will be placed in the failsafe mode. The switch is a 3-position mode switch that allows the pilot to tailor the intercom function to best meet the situation. I : (Up Position): The pilot is isolated from the intercom and is connected only to the aircraft radio. He will hear the aircraft radio reception (and sidetone during radio transmissions if provided by the transceiver). Copilot and passengers will hear the intercom and music on Entertainment input, but not the aircraft radio receptions or pilot transmissions. A: (Middle Position): All parties will hear the aircraft radio, intercom, and music from entertainment input. However, during any intercom communications, the music volume automatically decreases when SoftMute is active. The music volume increases gradually back to the original level after communications have been completed.

Speaker Amplifier

Pressing the volume control will activate the cockpit speaker. This switch will place all selected audio on the cockpit speaker when selected. The speaker is automatically muted when the radio push to talk (PTT) is active. To reduce power consumption and internal heat buildup, switch off the speaker amplifier when not in use.

Microphone (Transmit) Selector Switch

Microphone Selector

The up switch position is C8; 1. Both pilot and copilot will be connected to the Com l transceiver. While in the C8; 1 or C8; 2 mode, the intercom functions normally. Both the pilot and copilot have transmit capabilities on the selected transceiver. All hear the selected audio if the intercom is in the A== mode. Only the person who presses their Push To Talk (PTT), will be heard over the aircraft radio. Placing the toggle switch in the C8; 2 position will place pilot and copilot on Com 2. The PMA4000-Series has an automatic selector mode. Audio from the selected transceiver is automatically heard in the headsets and speaker (when selected). You can check this function by switching from C8; 1 to C8; 2 and watch the selected audio light on the selector change from C1 to C2. This ensures the pilot will never transmit on a radio is not listening to. When switching from C8; 1 to C8; 2 while Com 2 has NOT been selected, Com 1 audio will be switched off. In essence, switching switching the mic selector will not effect the selection of Com receiver audio.

Volume Control

The pilot volume control knob adjusts the loudness of intercom and music in the pilot’s headphones only. It has no effect on selected radio audio levels. The copilot volume control adjusts the loudness of the intercom and music in the copilot headset. The passenger volume is also adjusted by the copilot volume control. Most general aviation headsets have a built-in volume control, so volume can be adjusted “locally.” The copilot volume control is also controllable through the rear connector, so a tandem aircraft can adjust the volume from a different location. 

VOX-Squelch Control

The PMA4000 incorporates PS Engineering’s revolutionary IntelliVox® No adjustment of the squelch control is required. Through two individual signal processors, the ambient noise appearing in all four microphones is constantly being sampled. Non-voice signals are blocked. When someone speaks, only their microphone circuit opens, placing their voice on the intercom. The system is designed to block continuous tones, therefore people humming or whistling in monotone may be blocked after a few moments. For best performance, the headset microphone must be placed within ¼ inch of your lips, preferably against them. It is also a good idea to keep the microphone out of a direct wind path. Moving your head through a vent air stream may cause the IntelliVox® to open momentarily. The IntelliVox® is designed to work with normal aircraft cabin noise levels (70 dB and above). It loves airplane noise! Therefore, it may not recognize speech and clip syllables in a quiet cabin, such as in the hangar, or without the engine running. This is normal. For optimum microphone performance, PS Engineering, Inc. recommends the installation of a Microphone Muff Kit. This will not only optimize VOX performance, but will improve the overall clarity of all your communications.

Aircraft Intercom Modes Table

The audio selector panel has provisions for an entertainment input device. While in the ISO (Isolate) mode, only the copilot and the two passengers will hear the entertainment device. In normal operation, whenever a person speaks or if the aircraft radio becomes active, the music will automatically mute and then will gradually return to the original listening level when the radio or intercom activity ceases. If a stereo entertainment device is used, the left and right channels can be combined in the plug to provide full sound. 

Push to talk Intercom Mode

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). In the PMA4000 audio panel, the PTT intercom capability is added. To operate the PTT, Activate the panel-mounted VOX override switch. Then, the ICS PTT switch.

Internal Recorder System (11941, only)

The PMA4000 (part number 11941) has an available internal recorder option. This stores the last 60 seconds of radio traffic from the selected COM transceiver (the one selected for transmit). The recorder function is automatic. Pressing the momentary switch associated with the playback, will cause the last message to played (incoming radio and transmit sidetone). This will be heard in all headsets and speaker (if selected). To hear older messages, push the playback button repeatedly to “back up” the recorder, until the desired message is heard. Holding the IRS playback button for three seconds will stop the message playback and queues the system to the next preceding message. This allows quick access to previous messages. The recorder is a continuous loop, and newest ones will overwrite the oldest messages. The IRS has an internal squelch that prevents storing ‘dead’ air. A radio signal of more than 1 VRMS is needed to trigger the IRS. Therefore, if the IRS does not seem to be recording, increase the aircraft radio volume slightly.

Intercom Limitations

Any entertainment device connected through the PMA4000 must be switched off during take off and landing.

Emergency Procedures

In the event that the unit exhibits any anomalous behavior, such as an audio failure, transmitter failure, or other difficulty, the unit can be switched off in the following manner:

1. Placing the Intercom Mode Selector Switch (see Figure 1-2) into the “OFF” position.

2. Pulling the Audio Panel Circuit Breaker. This activates the fail-safe mode, which connects the pilot’s headset directly to Com 1. This allows communications or the pilot only, on Com 1 only

Warranty and Service

In order for the factory warranty to be valid, the installations in a certified aircraft must be accomplished by an FAA-approved agency and authorized PS Engineering dealer. PS Engineering, Inc. warrants this product to be free from defects in material and workmanship for a period of one year from the date of installation. During this one-year warranty period, PS Engineering, Inc., at its option, will send a replacement unit at our expense if the unit should be determined to be defective after consultation with a factory technician.

The customer is responsible for return shipment costs. This warranty is not transferable. Any implied warranties expire at the expiration date of this warranty. PS Engineering SHALL NOT BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES. This warranty does not cover a defect that has resulted from improper or unreasonable use or maintenance as determined by us. This warranty is void if there is any attempt to disassemble this product without factory authorization. This warranty gives you specific legal rights, and you may also have other rights that may vary from state to state.

Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above limitation or exclusions may not apply to you. Factory Service The PMA4000 is covered by a one-year limited warranty. See warranty information. Call PS Engineering, Inc. at (865) 988-9800 before you return the unit. This will allow the service technician to provide any other solutions beforehand.

• Has independent intercom volume controls for the pilot, and the copilot.

• A multi-position mode switch allows the pilot to select either Pilot Isolate or All intercom modes.

• The ISO mode isolates the pilot from the intercom, and connects directly with the aircraft radios. The copilot and passengers are free to have conversation and enjoy the entertainment without radio interruption. The pilot is not distracted by passenger intercom use and has control over the radio communications.

• The "ALL" mode places everybody on a party line. Each person hears all intercom conversation and aircraft radio reception. Everyone hears the entertainment source as well.

• The "Off" mode is part of the automatic fail-safe interconnect to the aircraft systems. If power to the intercom is disrupted, the pilot's headset is automatically connected to the aircraft radio. This permits continuous radio communications.

• By harnessing the computational power of microprocessors, the PMA4000 eliminates complicated squelch adjustments. Individual squelch controls mean that the system can be tailored to different microphones, as well as variations in voice levels in the cockpit.

• Has two switched com transceiver inputs and two switched navigation receiver inputs. In addition, there are four un-switched audio inputs that can be used for other receivers or audio warnings such as autopilot disconnect or GPS alerts.

• There is a built in speaker amplifier in the unit. Pushing the volume control will place all selected audio, or any un-switched audio present, over a cabin speaker.

• With the PMA4000 installed, both pilot and copilot have transmit capability over the aircraft radios. Only the person who presses the PTT is heard over the radio. The selected com LED shows green when selected, and flashes during radio transmissions. This feature acts as a stuck microphone indication.
  • DIMENSIONS: Height: 1.35 in. (3.4 cm) Width: 2.40 in. (6.1 cm) Depth: 6.50 in. (16.5 cm) behind panel
  • WEIGHT (With Connectors): 12.4 oz. (0.35 kg)
  • Voltage: 11 to 33 VDC (28 Volt w/dropping resistor)
  • Maximum Current: 0.25 Amp (Externally protected by a 3 Amp circuit breaker.)
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