I own three aviation headsets: - BOSE A20 - David Clark H10-13.4 - Compilot Lite (a cheap headset bought recently, for occasional use by passengers)

I tested the Compilot Lite last week (co-pilot side), but I ended up blocking the frequency at a local airport. Unfortunately, it took me some time, and somebody waving furiously at me, before I found out.

I was wondering how this issue could occur and what could be wrong with the headset. I found an explanation on this forum, which states that the tip of the connector functions as a PTT button when grounded. However, the connector does not seem to differ a lot from the other headsets. Left = Compilot, middle = DC, right = Bose.

enter image description here

Could it be caused by something else? The type of microphone?

Any tips or suggestions are welcome.

Thanks! David

PS the aircraft was a C172N, a rental which I often use, but never had this issue before with the other headsets

  • $\begingroup$ @mins the one on the right is a Switchcraft mil- spec M642/5-1. It is a 3 conductor plug. The others are generic PJ-068 connectors. They’re supposed to be compatible with each other. $\endgroup$
    – TomMcW
    Commented Nov 25, 2017 at 20:17
  • $\begingroup$ Could be a wire broken or grounding out somewhere past the jack itself. The headset might be fine to use as designed, but with a broken/grounding wire, it ends up being a continuous hot mic. I flew with a pilot several years ago whose headset would occasionally create a hot-mic because its wires were so worn out, and of course we were the only ones who couldn't hear it. Perhaps your headset is doing something similar, but continuously. Maybe an avionics shop could take look at it? $\endgroup$
    – Ralph J
    Commented Nov 25, 2017 at 20:24
  • $\begingroup$ @TomMcW: You must be right. Searching a bit I understand that the Bose has a 6-pin jack and needs this adapter to get usual jacks, of which the one in the post. $\endgroup$
    – mins
    Commented Nov 25, 2017 at 20:25
  • $\begingroup$ @mins That’s a LEMO connector, which is an option on Bose products. But the connector he is showing is the .206” phono connector. The A20 can be ordered with either type $\endgroup$
    – TomMcW
    Commented Nov 25, 2017 at 20:30
  • 1
    $\begingroup$ @MichaelKjörling Yes, the mil spec connectors have an extra piece of metal between two halves of the insulator between tip and ring. see drawing $\endgroup$
    – TomMcW
    Commented Nov 25, 2017 at 23:02

2 Answers 2


Apparently the tip connection is being grounded activating the PTT. From the photo the only thing that could possibly be a problem is the Compilot plug being a tiny bit longer than the DC. But the detent in the tip is what should decide where the plug sits in the jack and that looks fine. It almost has to be a wiring problem in the Compilot. If you have a multimeter check for continuity between the barrel and the tip. There should be no continuity unless a PTT button is being pressed.

  • $\begingroup$ Thanks for your feedback! I have used a multimeter, but could not find a continuity on the plug. I also connected this headset to my handheld radio (iCom) and after moving the cables around, the issue was there again. So, indeed a fault in the wiring .. I guess it is Murphy who makes it harder to find when not in an airplane :-) $\endgroup$
    – David
    Commented Nov 26, 2017 at 8:21

The issue has been found ... the headset cable was damaged. One of the audio cables was slightly exposed, causing it to touch the ground (which is the shield of the cable and is not covered). This only causes a continuity when connected to a radio, so it was hard to find ...

Kind regards, David

  • $\begingroup$ Good that you found the problem. I guess that goes to prove, at least to some extent, that you do indeed get what you pay for. $\endgroup$
    – user
    Commented Dec 1, 2017 at 15:27

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