On Mar 28, 2014, at 4:16 PM, Fred Cisin <cisin at xenosoft.com> wrote:
...
In order to make it more difficult to properly use the 500 series
Filmosounds, they had a non-standard socket for the audio out. Instead of
1/4", it was slightly smaller (maybe 6mm?) We, of course, made short
adapter cables.
Sounds like the obsolete standard slightly-smaller plug you still find on aviation
headsets. I?ve also seen that on WW2 era transmitters or receivers; forgot the details
but it might be that 1/4 inch was used for headphones and the smaller one for the
microphone, or perhaps one was for headphone and the other for telegraph key.
paul