While sorting through my "collection" of junque microphones,
I found a desk-type mic with
* a fairly thick and heavy base with
* a four-wire cable,
* an RCA logo on the front, below and to the left of
* a plastic horizontal TRANSMIT bar, and
* a sticker on the bottom which says (and sorta looks like):

SHURE BROTHERS INC.
Controlled magnetic microphone
Model #MI-559156-1
Made in Evanston, ILL., U.S.A.
U.S. Patent D-198,850

In addition to the expected switch, the base also hides a one-transistor
something (presumably an amplifier). By treating the "amplifier" as a
three-terminal device, the wiring was simple enough to trace:
* two wires for PTT and
* two for audio
and it did work with my HF radio, although the mike did NOT seem very
sensitive.

Does anyone have any information about this mike and/or the radio it
might have originally accompanied? Since there is no provision for
an internal battery, I wonder if its radio supplied a voltage on one
of the audio wires?

--W0PBV.
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
NRA Life Member & Certified Instructor for Rifle, Pistol, & Home Firearm Safety
Also Certified Instructor for the Kansas Concealed-Carry Handgun (CCH) license