View source for U-229

;Pin A Common Ground
:The common ground for audio and is typically the same as chassis ground.  

;Pin B Handset speaker
:Audio output to the handset speaker.

;Pin C Push To Talk
:When grounded it puts the transmitter into transmit mode

;Pin D Mike
:Microphone input to the radio.

;Pin E Not Standardized
:Different radios use it for different purposes.  For example:
PRC-68 Family of Squad Radios uses pin E for "12 Volt" vehicle power input.
:The HF manpack radios PRC-74 and PRC-104 use pin E for the CW key input, and it's also used for high speed CW like from a GRA-71.  Note that the pin C PTT line can NOT be used for CW keying on a radio that supports SSB operation, since there would be no output.
:The VRC-12 series Squad radios uses pin E as the loudspeaker line to drive the LS-454.
:The PRC-25,  PRC-77 AUDIO and the RT-246, RT-524 & R-442 RETRANS use pin E as the retrans PTT to key the other RT with the Mk-456 Retransmission Kit.

;Pin F Not Standardized==
:This is the center pin that is not present on a true U-229 connector.  Many radios install the 6 pin version of this connector, yet do not connect a wire to pin F.  Maybe it's done to allow a future modification, or maybe just to standardize the connector?  Some equipment does use this pin where the other pins are used in the above audio functions, for example:
:The PRC-68 Family, except the PRC-68 and PRC-68A, use this pin for digital up and down loading of the channel frequency assignments and as the retransmission PTT output.  This supports a retransmission cable and cloning cable that are different than the Mk-456.


[[File:U-229_assembly.png|400px]]

==U-229==

==U-228==

==GC-328==

==U-183==