[GreenKeys] TTY Speeds

[Sheldon Daitch]

Well, now you are asking me something that I am not sure I can answer.

Let me give you what I think is the non-technical answer and what I think
I remember from way back, with a few guesses.

I was not working with the AP at the time of the conversion, as I was still
a teenager, but I seem recall that my little home town radio station had
to do the conversion in house.  Since this was a
total state changeout, it would have been nearly impossible for the
AP to field enough folks to convert the state with individual field trips, so
I am guessing that some stations may have elected to do (or try ) the
field conversion.  If the station could not make the conversion, the
worst that could happen is they had no news service, which is
exactly what would happen if they waited for a tech to do the
conversion.

Maybe the stations did not have to change the mainshaft
gear, as the AP might have supplied converted printers already set up
with the proper gear on the main shaft, and all that had to be changed in
the field was the motor gear and then put the new printer on the base.

The AP had a gear combination that worked out for 66 WPM, and
the speed change was not done by shortening the stop pulse, I don't believe,
but by actually speeding up the mainshaft rotation rate.

At one time, I had a souvenir set of gears for that speed, and I don't think
the numbers were in the Teletype parts lists, as I think it was made for the
AP exclusively.  I think this was done sometime in the 1960s, and perhaps
the speed change was done as a compromise between getting more
information on the circuit without radically changing the speed of the M-15 and
severely increasing the maintenance requirements on the equipment.

Sheldon








jhaynes@alumni.uark.edu wrote:

> When you say the AP ran at 66 WPM, does that mean 50 baud?  Or 45.45 baud
> with 7.0 unit code?  Either of which gives about 66 WPM.
>
> As long ago as 1938 the standard speeds were approximately 40, 60, and
> 75 WPM in the Bell System. (Source AT&T Green Book, "Principles of
> Electricity..." 1938 edition.)  That would mean Model 14 and 15 equipment,
> since the 28 did not yet exist.  During World War II there was some
> operation at 100 WPM, where it was felt the urgent need for traffic
> carrying capacity outweighed the high maintenance requirement.
> (Source, Bell Laboratories Record, April 1948, p 165.)
>
> In the late 1950s I saw a Model 15 operating experimentally at 100 WPM at
> the FAA center in Oklahoma City.  They wisely gave up on that and decided
> to replace their machines with Model 28s.
>
> The XD transmitter-distributor had no trouble running at 100 WPM.  The
> late model ones were fitted with Model 28-style clutches replacing the
> felt friction clutches for better operation at 100 WPM.
>
> _______________________________________________
> GreenKeys mailing list
> GreenKeys@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/greenkeys