Had a customer in the office yesterday. One of those conspiring against you ones. Really nice guy with a powerboat racing helmet, piles of cables and a Retevis radio that had no transmit audio.
The helmet is like a fighter pilots one, but full face, with internal respirator, containing the mic. It has an air tube. The earpieces are custom moulds. One cable goes to the boat PTT circuit, the other through moulded cables, to the Retevis plug. The connectors are 4 circuit nato type and each helmet needs a dedicated nato female to male which also provides the correct connection via another adaptor cable male to male that seems, by testing, to offer different connection permutations. Two hours, and a spliced cable and i could not make it work. Obvious continuity tests failed, and i was stumped. Worse was that he only had one radio. Eventually i had to download software and discovered that it had CTCSS on receive, digital on transmit, and a non-standard and illegal frequency. With my other radios I struggled to get them to transmit to it, but eventually got there.
We aborted it because we both needed to be places. The answer came at 4am. I bet the connection to the boat means that there is also a socket so a headset can be plugged in in the pits for two way talking, not radio. So the PTT is not just a circuit close, but carries the audio. I determined the PTT pins in that connector, but never thought there would be a need for the audio to be going through other pins, and i never did continuity at that connector. Have you ever woke up in the night with a solution? Not certain of course, but its another stream of possibilities but i cannot fix it in the office, and i really dont want to be soldering on water!