21. February 2020 by Peter
I have an OEM Audio Control Panel (ACP). That means it is a panel from a real aircraft. It is from 1992 and I has been installed in a 737 Classic like the B737-200.
The Audio Control Panel allows the pilot to adjust what I wants to hear and at what volume. Inside the ACP each source can be selected with a switch and the volume adjusted with a potentiometer. There is also amplifiers inside. So all audio processing happens inside the box.
In a simulator the logic is different. Here you have on/off switches and potentiometers and the value of those is sent to the computer. The computer then calculates which sounds should be played. So the box is just buttons and switches.
I mounted it in my pedestal last month. Knowing I not was able to use the audio logic inside the box I did however interface one of the switches. It is used as PTT (Push To Talk) button. Further more the signal is sent to an audio relay that allows the sound from the captains headset to be transmitted to VATSIM.
However I did face a few problems with the switch. Sometimes it would stick / not release. So today I took it apart ready to replace the switch. Then I remembered that I hear the switch click back. To using a multimeter I realised that the switch worked but the problem is in electronics.
I have only supplied power for the backlightning. Not the box it self which requires 24 v. Instead of powering up the entire board I choose a Plan B and simply bypassed the board.
I drilled a hole for an aviation plug on the back of the box and ran wires directly from the switch to the plug bypassing everything inside the box.
How the PTT works flawless.