This microphone is in the U-77 family the preceeded the current U-229 family of military audio accessories.
The U-77 family all use carbon microphone elements whereas the U-229 family uses dynamic microphone elements.
Microphone Carbon M-29B/U
While this is a hand mike with a Push-To-Talk switch it uses the M-51/UR carbon microphone element.This element is also used on:
Headset Microphone H-62/U, H-63/U
Aircraft Boom Microphone: M-3/A
U77 Audio Connector
A - Receiver Audio
B - Receiver Audio Ground
C - Carbon Mike Input (Red)
D - mike ground (Blue)
E - PTT then Mike (Green)
F - isolated Push To Talk (Brown)
H - isolated PTT Ground (Yellow)
J - Remote On-Off
K- CW Key
L - Speaker
Note the U77 connector has provision for either full duplex telephone use by means of microphone pins C & D, or radio use by means of pins C and E where PTT must be pressed for the mike to be active.
Note that the wire colors are much easier to see under LED light.
C (Red) to D (Blue): 10 k Ohms
At Switch (Fig 2)
Switch: DPST circuit 1: Mike-conn Blue (D) & conn Green (E), circuit 2: conn Brown (F) & conn Yellow (H)
Mike: switch Blue & Mike Blue , Red (C), Conn White (lanyard to coil cord)
Audio Connectors & Cloning - Fill - Retransmission
Military Audio Accessories - Small Photos
U-229 Audio Accessories - Separate web page
U-229 Pinout by Function - seperate web page
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