Oxy mask connection

[exftrplt]

When connecting the oxygen mask microphone U173/U to the microphone cord with a U172/U connector, are these pins polarized or can they be plugged in either way? It is just grounding the mic. wires. I can't see how they could be polarized. However in some airplanes when I plug into the airplane all is good and on some airplanes when I plug into the airplane squealing results. Me or airplane?? Am I looking at the wrong thing? Could it be airplane wiring?

[rwanttaja]

Seems like if polarity was important, they would have designed the individual posts differently. In this shot, they look identical
9533

Oddly, on another shot I took, the posts are actually different...but STILL not different enough for a polarization guide.
9532

If you can, in the squealing cases disconnect the U173 and turn it the other way.

Ron Wanttaja

[Dana]

If it's an old fashioned carbon or dynamic microphone, polarity shouldn't matter. If it's a modern electret mike, polarity will matter.