I think pages 16-17 of the brochure give a good example of the primary use of suppression and zero code bars, which is in selective calling (sel-cal). 
The “hook” is there so the printer is always active as you’d want it to be for local or dedicated use. 

There’s also some material in the RTTY Journal stunt box articles. 

But I have no experience from back in the heyday of ham RTTY. Hopefully some of the guys here who were involved in the autostart nets, playing LF tricks on friends, etc. will speak up. 

Nick England K4NYW
Chapel Hill NC
www.navy-radio.com


On Sun, Oct 12, 2025 at 2:51 PM John Doe <jdoe10449@gmail.com> wrote:
Hello all,

Restoring my M28, I noticed that the SUPPRESSION code bar is permanently hooked in the marking state with its actuator link disabled and the ZERO code bar doesn't have a detent - so is sprung to the marking state but is otherwise free to move. I can see rub marks on the SUPPRESSION actuator links so I know it was operating at some point in the past. I'd like to figure out why it was disabled to restore functionality. Photos attached.

The manuals and stunt box brochure explain how they work, but not many practical examples. I'd like to know more about the SUPP. and ZERO code bars before I go on the hunt for shift forks, pawls, function bars, etc.

Any help appreciated.

Thanks,

Nicholas Gromak
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