[ARC5] "Retaining" plugs

[Mike Morrow]

Mike/W4DSE wrote:

> I think I remember reading someplace that the "knurled ring"
> on the BC-451 control box is not a retainer, but actually some
> kind of switch that works in conjunction with a PTT switch on
> the stick grip of the aircraft, when a throat microphone is used.

True, it is not a retainer at all.  But there's also no indication
of the transmitter control box what it does.

Here's what the ATA/ARA Instruction Book says about the microphone
jack on the transmitter control box:

"Microphone jack J-65 is constructed in such a manner that the sleeve
may be grounded to the box, or not, by turning the protruding knurled
nut counter-clockwise, or clockwise respectively as far as it will go
by hand.  In the counter-clockwise position the sleeve is grounded and
the "push-to-talk" button on the microphone will close the microphone
and relay circuits to ground when actuated.  With the nut in the maximum
clockwise sense, the "push-to-talk" button may be locked closed after
which the pressing of the built-in key, external key, or throttle switch
will perform the same function as the "press-to-talk" button did when
the knurled nut was in the counter-clockwise position."

The "sleeve" referred to above is the long shank of the microphone plug.

The knurled nut is almost always found, as one would expect, turned to
the maximum CCW position.

This type of microphone jack is found on both the ATA CBY/CCT-23243
transmitter control box, and on the SCR-274-N BC-451-A transmitter
control box.  There is nothing similar for the AN/ARC-5 and its
various J-16 and J-22*/ARC-5 audio jack boxes, or C-39 and C-48/ARC-5
auxiliary control boxes with audio jacks.

Mike / KK5F