[GreenKeys] M15

[Sheldon Daitch]

Jim,

I can't speak for the UPI at a higher speed for the M-15s, but the AP was running them at 66WPM toward the end of the life of the M-15s.

I have a vague recollection of the AP converting Georgia over to 66 WPM in the mid  60s to early 70s.  What I don't clearly remember was how the AP made the conversion....did they send out totally "new" machines or did they send out "new"typing units with a new motor gear and ask the stations to replace the motor gear and swap the typing units.

I think you hit it on the head re the M-15 at 100 WPM, that the AP may have decided that the increase from 60 to 66WPM didn't involve a large increase in maintenance, while going to 75 WPM would have increased the traffic capacity, the maintenance involved wasn't worth the effort.

Another aspect of the AP, and probably also applied to the UPI as well, that at some point, the AP converted from a DC loop system, where the DC loop came from the telco, to the AFSK tone pack system, using the Lenkurt 25 carrier system, that it might have been easier to simply add an additional machine for extra services rather than try to cram more material down one circuit.

This probably wasn't much of a deal for the radio and TV news circuit, but over on the newspaper side, over in North Carolina AP service, I think there was a slow speed 66 WPM circuit for the morning newspapers, one for the evening newspapers.  The market reports, were two slow speed circuits, one for the first half of the markets, second wire for the second half of the report.  I am inclined to think there might have been another service or two for the newspaper side, but I am not sure.  Also, those newspaper circuits were M-20 six-level Teletypesetter coding, but the motor and mainshaft gears were the same as for the five-level machines.

73

Sheldon



-----Original Message-----
From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Jim Haynes
Sent: Tuesday, April 14, 2015 5:17 AM
To: COURYHOUSE at aol.com
Cc: Til128 at aol.com; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] M15


My understanding is that it was designed to go to 75 wpm.  Or maybe was originally designed for 60 and then was found satisfactory at 75, perhaps with a few changes.  What I don't know is who used them at that speed.
We know AP and UPI ran them at 60 wpm.  Seems like the wire services would most benefit from the higher speed, except maybe they still into the 1940s had some Model 12 machines in service.  TWX stayed at 60 wpm until the cutover to dial TWX and 8-level machines.  A.P. went so far as to convert their machines to 50 baud - I've wondered why they didn't go to 75 wpm instead.  So it must have been largely private services that used 75 wpm.

We know that in WW-II the military made some use of 15s running at 100 wpm, accepting the need for increased maintenance to get the higher traffic capacity.  I would assume that was largely on land lines within CONUS, since we never encounter old military machines from the field set up for 100 wpm.

Another large user of TTY equipment was the CAA/FAA and Weather Bureau, but I believe they operated at 60 wpm until the cutover to ADIS about 1960.  By then they had pretty much phased out the 15s in favor of 28s.

In message switching systems such as 81D1 it is desirable to operate the cross-office circuits faster than the out station circuits, and the cross office circuits could operate at 75 wpm, but there was no need for printers on those circuits.

So who were the 75 wpm users?

On Mon, 13 Apr 2015, Ed Sharpe Archivist for SMECC via GreenKeys wrote:

> 75 wpm is  booking along   for a  15! It has a nice  sound!
> I rather  like it.... but     I wonder what the wear  factor is..?
>