[ARC5] Microphone Element

[Jim Haynes]

I repeat myself from time to time on various groups, so if you've seen 
this before please just ignore it and don't complain.

It's my belief that the original T-17 carbon transmitter even when new
was intentionally quite insensitive.  They were used in airplanes, and
it was necessary to yell into the mike to be heard over all the airplane
engine noise.

In earlier times when someone wanted a functional microphone and didn't
care about historical authenticity, it was common to use electrical tape
to attach an F-1 telephone transmitter to the front of a T-17.

The more recent T-1 telephone transmitter used in the "500" type 
telephones is smaller and better than the F-1, but is just barely too
big to fit inside a T-17 housing.

You can get electret drop-in replacements for the T-1 transmitter.
I got them from Mike Sandman, and they are quite cheap.  The standard
part is intended for a telephone handset with a modular connector,
but can be carved up to fit into a non-modular hanset.  And you could
probably carve it up further to fit inside a T-17.  Or just build the
circuit from parts and stuff them in there.  You don't need the diode
bridge if you can be sure the polarity applied to the mike is always
the same.

I've attached a schematic of the T-1 replacement, and also somebody
else's hand-drawn schematic for doing the same thing.
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