[GreenKeys] A note of thanks!

[Paul Wills (CKT&T)]

What's nice is that you can slowly operate the main shaft and manually 
operate the magnet to see how it works.  After a few hundred spins, I 
finally started to figure it out.

PDW

On 10/14/2020 3:51 PM, Jim Haynes wrote:
> On Wed, 14 Oct 2020, Harold Hallikainen wrote:
>
>> My notes for model 15 are at https://w6iwi.org/rtty/
>>
> A great thing about the Model 15 is that it is pretty easy to understand
> and explain to people.  For basic TTY theory there is the AT&T book
> Principles of Electricity Applied to Telephone and Telegraph Work.  At
> least one edition is available online.
>
> Once you have the basics it's pretty clear how the thing works. Selector
> magnet, cams, swords, etc. are explained in the AT&T book. That shows
> how you get started and stopped every character and deserialize the bits
> of each character into five positions of parts.  Five of the vanes
> make that information available across the width of the typing unit.
> Bellcranks transfer the information from the vanes to the code bars,
> and that's where the decoding takes place.  Then the cam that powers
> the printing bail to fling a type bar at the paper.
>
> Behind the vanes, the function bars that decode the functions: LTRS, 
> FIGS, etc.  The sixth vane that allows functions to be limited to 
> either LTRS or FIGS case.  Underneath the machine the function bar 
> ends push up bars to engage a cam-operated bail to do things like 
> shift the carriage up or down, ring the bell, suppress spacing, etc.  
> The spacing mechanism that drives the carriage across the width of the 
> machine.  What is a little bit tricky is the mechanism that prevents 
> it from moving more than one space at a time.  As our old machine shop 
> instructor would say, "That's all they are to it."
>
> The keyboard code bars that move right or left according to which key is
> pressed.  They engage cam followers that allow or disallow the contacts
> to close as the transmitting shaft rotates.  A little tricky mechanism
> to insure that only one character gets generated per key press.
> _