[GreenKeys] Real TTY, etc., etc.

[jhhaynes at earthlink.net]

I used to mean to ask some old hands at Teletype how the odd number of
1.42 for the stop pulse was arrived at, but I never did it.  And now 
they are just about all gone.  Western Union used 7.0 code to get the
higher WPM with the same Baud number.  Seemed to work OK for them.
7.5 code I think came from Europe and got into the Model 32 since
W.U. wanted them for Telex.  Model 33 got 11.0 code because they just
couldn't design a selector that would work reliably with 10.0 code
at 100 WPM.  That's how we got 110 baud.  

The K6STI RITTY program has an output while receiving so you can
feed the RS-232 data through a converter to a Real Teletype machine
if you wish.  That's the best of old and new worlds; you get the
best digital signal processing demodulator and you can print on the
old machine.  Wish we could get the author of MMTTY to put in a similar
feature.  If you wish you could use a KSR and transmit from the keyboard
and use the RITTY software only for receiving.  (And if you wish you
could rig up a keyboardless, monitorless PC that would run the RITTY
software all the time out of sight, so it is functioning only as a
TU.  Now that would be the old and the new.)

Agreed that diddle is undesirable for a mechanical printer, but helpful
for the RITTY kind of demodulator and useful with some of the hardwired
TUs.  My original idea was to have a circuit that would delete the
surplus diddles from getting to the (mechanical) printer; but I never
got around to implementing it.  Would be slightly harder now that
people are using a variety of diddle characters, but I suppose with
a UART and some logic in between the receive and send sides you could
do it.  Set the sending side up to send 7.0 code to the machine, and it
would get stretched out to 7.42 or whatever since the characters don't
arrive any faster than 60wpm.

And I guess with Gil's board there could be a firmware excess-diddle
deleter.  

My original plan used LTRS and FIGS as diddle characters, depending on
what case the machine was in.  (Which meant an unshift-on-space option
in the diddler as well.)  But seems like some people use blank for
diddle these days, and some just use LTRS.  Blank is a non-printing
character in most character sets and can ge safely discarded; but in
the no-longer-used weather symbol character set it was a printing
character.

-- 

jhhaynes at earthlink dot net