Hello
as we can see on yours microphone respirator, i think they wher used for the artillery transmission système.
We can see on the loud speaker control box the same connector as you have on your respirator for remplace the standart microphone in case of gaz alarme.
Photos from
https://hatchfive.wordpress.com/category/radio/
link :
http://www.mapleleafup.net/forums/sh...d.php?p=226775