[GreenKeys] The Iron Horse in action...

[Duncan Brown]

The AWA just got a large donation of what had been a WU Museum, 
including lots of books & manuals from the 1920-30s, so I have been 
trying to learn more about the original Printing telegraph equipment.

I would say that this picture is of a multiplex system, not start-atop, 
since there is no distributor mounted next to the tape reader. One of 
the WU books showed good pictures of some of this equipment but did not 
always tell who the manufacturer was.  The box mounted behind the tape 
reader is a hand operated, Kleinschmidt Electric device, that generates 
FIGS, BELL, LTRS by the push on a lever; so that the bell signal could 
be inserted with out removing the tape.  (not sure why they needed this 
feature, may be to send warning of high priority message coming)

The inventor of the 5-bit code was a Frenchman, named Emile Baudot 
(1845-1903), but he did not use perforated tape. His system (about 1875) 
transmitted from a 5-key piano-style keyboard that was operated with 
both hands. This keyboard (in parallel) fed a distributor (parallel to 
serial converter for you computer types) that put the signal out onto a 
two-wire serial line, multiplexing it with up to 3 other circuits. The 
operator had to know the 5-bit code and hold down the keys at the right 
time, when told to by the distributor. This 5-bit code was different 
from the one we are familiar with, as it was designed for ease of 
learning and included French characters.

Donald Murray (1865-1945) of New Zealand, was the first to use the 5-bit 
perforated tape. In 1890-1900, he perfected the 5-bit Baudot code by 
making the most common English letters require the least amount of 
mechanical movement in the machine. He also added “carriage return” and 
“line feed” functions. His system used the same multiplex system that 
Baudot used, but a tape was perforated by a keyboard-operated machine, 
similar to the Teletype Corp.’s GPE perforator. The tape, after being 
punched by the keyboard perforator, was fed into a tape reader that read 
the punched holes in parallel and sent them to the multiplex distributor.

(the above two paragraphs from an article that I just wrote for The AWA 
Journal.)

One of the articles that I read recently talked a lot about how using a 
perforator and tape reader improved the throughput of the system over an 
operator typing directly to the line.  It was something to the effect 
that a typist's speed varies, but if typing directly to the line, their 
speed could never be greater than the line speed and thus their average 
speed would be less than the line speed.  With the perforator and tape 
loop (buffer) between the typist and the tape reader, the tape would 
always be going out at line speed. (I had always wondered about why they 
typed to tape, and now we know the reason!)

This analysis of the speeds comes from "The Development of Printing 
Telegraphy," written in 1921, by J. O. Carr, Chief Engineer of the 
Morkrum Co.  You can view it at *
*https://books.google.com/books?id=Z0wyAQAAMAAJ&pg=PA124&lpg=PA124&dq=Wheatstone+Mallet+Perforator&source=bl&ots=nnb_QW2imO&sig=uKKDfCs0oKCT9dGvnBNvI-cCEiE&hl=en&sa=X&ei=cDyLVO__GtKcygSR5ICQAQ&ved=0CCIQ6AEwAQ#v=onepage&q=Wheatstone%20Mallet%20Perforator&f=false
(this link takes you into a slight diversion about the Wheatstone 
perforator, but the rest of the article is all printing telegraphy and 
starts at p116.  If you download a PDF version, the article can be found 
at PDF page 243.)

The article includes details about the Teletype Corp. M11 (but nothing 
about the M10).

have fun,

Duncan

On 17-Dec-14 21:46, Jim Haynes wrote:
> The reader looks like the front end of the later XD Model 14 reader,
> but with a base with slip connections so it can be connected to an
> external distributor.  And hence presumably magnet-driven.  So this
> could be start-stop or multiplex.
>
> jhhaynes at earthlink dot net
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