GE EM28A Controlled Magnetic microphone similar to Shure 450 - a few questions

[AB3OL]

Have a GE EM28A Controlled Magnetic microphone made by Shure. From what I gleaned from internet searches it is similar to the Shure 450 mike.
Has a 4 pin keyed round plug which appears to be molded on to about 5 feet of black straight cable. The PTT switch is not locking and appears to short out the mike contacts when not depressed. The base has the hole for a DP slide switch to change from low to high impedance but there is no switch present. Questions are:

1. What is the impedance of this mike?

2. What is the mating female 4 pin connector and where can I get one?

3. Will this mike work on a Ten Tec Omni C HF transceiver?

4. If the wrong impedance can I add the components required to change impedance like Shure did on the 450?

Would like to use this mike on a Ten Tec Omni C which has a 3 conductor 1/4" phone jack as its mike input. Would like to make an adapter to take the existing 4 pin plug to a 3 conductor phone plug without destroying the existing plug and cable.

If anyone has a schematic or manual for either this mike or the 450 I would appreciate getting it.

[W9GB]

Henry -

This is an easy question to answer.
Shure has scanned (PDF) their User Guide library and placed these in
the Support section on their web site.

Shure 450 Series II - Product Page
http://www.shure.com/americas/produc...top-Microphone

Shure 450 Series II - User Guide
http://www.shure.com/idc/groups/tech...eriesii_ug.pdf
===
Shure 450T User Guide -- Discontinued model (3 options)
http://www.shure.com/idc/groups/publ...ro_450t_ug.pdf

These microphones used the Shure R96 Lo-Z (~ 200 ohm) microphone element.

Use the Owner's Manuals for your Radios to complete the wiring of this microphone.