[GreenKeys] Morkrum M12

[Duncan Brown]

On 06-Dec-14 16:13, epvgk at limpoc.com wrote:
> Interesting to see pre-M15 era equipment. I wonder what that is 
> printed on the paper sitting in it? Always curious about remnants from 
> their original use... eric 

Eric - I think it is just RYs and "Now is the time for all good men..."

Jack - Thanks for mentioning "The New RTTY Handbook" - it has a good 
section on the M12 that I had ignored in previous readings of the book. 
But the schematics show modifications for Ham use and leave some 
questions on how it was wired originally.  I have Bul 110 on the M12, 
but it is just the printer and mainly adjustments. The schematic of the 
printer shows the five selector magnets and the "sixth pulse" (print) 
magnet.

Jim - The keyboard in the M12 that I sent the picture of looks like a 
serial keyboard  with 6 contacts very similar to the M14/15 (so it is 
setup for start-stop) and then a separate set of cams driving contacts 
for the selector magnets in a serial to parallel conversion. A 
polar-relay does the start-stop on receive. The RTTY Handbook says that 
the selector magnets of the printer were latching and released by the 
"print" magnet. So this "receiving distributor" on the keyboard module 
converts a serial input signal to the parallel setup of the printer.

Was the M12 originally a parallel machine - both sending and receiving - 
and pre stop-start come??  Is the M12 keyboard we are familiar with a 
modified one to allow use on serial lines?

My TTY background was Kleinschmidt Labs TTYs in the Army.  Being 
designed in the late 1940's, there was no parallel operation history and 
everything was designed to be serial. There were no 
"Transmitter-Distributors", just keyboards & tape readers that read each 
bit sequentially.  The first time I saw a M14 "T-D" I was surprised by 
how big it was. Then I learned about the big "distributor" inside 
because the M14 tape reader sensed all the tape holes at once (in 
parallel).   I assumed the early units ran a parallel signal, but why 
didn't they just change the tape reader cams when everything went 
serial. (I know, companies can have a lot of inertia!)

I guess the ways a product evolves may not seem straightforward or 
logical to us at a later date. Were all the early printers & reperfs 
designed with five magnets and then someone finally made the 
"Breakthrough" of figuring out how to do it with just one magnet?

The Kleinschmidt Electric M20A tape printer in the AWA Museum has 5 
selector magnets and a print magnet (no motor).  There does not seem to 
be any latching mechanism on the selector magnets, so it seemed to me 
that it must have been used in a true parallel system (no RX 
distributor), where multiple machines were wired in parallel and the 
data was put on the 5 lines (aka data bus) and held until the signal on 
the print line (aka chip select) was received by a specific printer.  
But I have never seen anything in print supporting this, so guess I need 
to do some more research.  We received a lot of documentation with the M12s.

Guess I have rambled on about this long enough.  Any comments??

Duncan
K2OEQ


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