[GreenKeys] Regenerative Loop Driver for Model 15 Teletype

[Mike Douglas]

 Jim,

One of my main goals with this project is to use the Model 15 as an operator console with my vintage computers (e.g., Altair 8800, IMSAI 8080, etc.) in the same manner as I use my Model 33. This requires full duplex operation, and therefore, separate send and receive loops. But I'm a child of the computer age, so Irv Hoff and I have different goals for the equipment :)

Mike

     On Wednesday, December 8, 2021, 03:10:48 PM CST, Jim Haynes <jhhaynes at earthlink.net> wrote:  
 
 That's very interesting - using such modern technology to drive an ancient
Teletype.

"Back in the day" Irv Hoff was always insistent that the Teletype keyboard
and printer should always be simply in series, and his "Mainline" stuff
always worked that way, so there was a single 2-conductor cord between the 
machine and the electronics.  I was not particularly taken to that point
of view, and in fact my designs at the time worked around converting the
Teletype external interface to something related to RS-232.

But I did fiddle around with, never built, a "leg combiner" circuit that
allowed the keyboard and printer to be simply in series in a loop but
provided separate receive and transmit legs.  The trick is to detect 
whether a spacing signal came from the keyboard or from the receive leg,
which involves setting a latch.  If anybody wants to look at this circuit
just ask.

Jim W6JVE

     ---

     "Ya can argue all ya wanna, but it's dif'rent than it was."
     "No it ain't! No it ain't!  But ya gotta know the territory."
         Meredith Willson, The Music Man
  
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