[GreenKeys] 14-15-19 Etc. motor

[Duncan Brown]

On 05-Jul-18 15:13, Ralph Mowery wrote:
> The motor will run fine at 60 hz.  Only problem is that it will run faster
> than it needs to be for the teletype machine.  While not exactly correct, if
> used in a 60 wpm machine , it will make it more like a 70 wpm machine.
Even if the motor did run a little fast, it wouldn't matter (70/60= 
+16%). Our ITA2* machines are not synchronous!  The machines  only need 
about 20% of each data pulse to make the 1/0 decision. This means that 
they can have perfect copy at speeds up to about 10-20% different from 
their design speed. Try copying DDK or ITTY-Europe with your 60 wpm machine.

These machines were designed to run over 10-20 miles of telegraph wire, 
which produced a lot of distortion. The Range Selector was used for 
finding the best point at which to read each data pulse in the presence 
of distortion. If your TTY is connected through only a few feet (as 
opposed to miles) of wire to a "modem" (wireline or radio), there will 
be little or no distortion and the extra "slop" in reading the data bits 
can be used to copy  other speeds.

If your TTY's Range Selector is optimized for 60wpm, it should copy a 
clean 66wpm signal 100%, though you won't have the range you had at 
60wpm.  However, if it is a clean signal, it won't  matter. You can 
readjust the Range Control for 66wpm if you need to.

*ITA1 was Emile Baudot's original (1883) system, which was synchronous. 
It was used up into the 1930s-40s, but there were always problems 
keeping things in sync (mechanically!). That is why the Krums invented 
Stop-Start in ~1920.

Have fun,

Duncan
K2OEQ



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