[GreenKeys] a couple more M15 questions

[jhhaynes at earthlink.net]

The TG-7A and TG-7B are both the field models where the packing case
serves as the table when the machine is set up.  The difference is that
the B model has somewhat simplified wiring, no provision for a polar
relay.

I don't imagine the military had any use for the fractions character
set.  They would use the communication set, probably with the slashed
zero, and sometimes the weather set with the wind direction arrows and
cloud coverage symbols.

I don't have an analysis chart for Model 15s.  If it's on your edition
of the Teletype Manuals CD ROM (if not I can send you a later one) under
Other is 1164B which is a keytops and type pallets catalog.  You'll see
there are lots of variations - there are 52 different type pallets having
C in LTRS case and something else in FIGS for the Model 15.  Typically
they defined an "arrangement" which was a complete set of type pallets,
and similarly for keytops.  There was a two-letter or three-letter code
for an arrangement; and when you ordered a machine that would be part 
of the order.  e.g.  BP4AG  would be Model 15 printer (BP), the fourth
major model, and having the AG type pallet arrangement.  The Bell System
would standardize on a few arrangements, so a 15A printer would be a BP
of some particular model and some particular arrangement, and a 15B would
be a different combination of those, and there were only a handful of
different codes.  Probably for a good customer, depending on the number
of machines involved, they would either define a new machine or would
change type pallets in the shop or in the field.  Teletype would make
just about anything a customer wanted, probably without insisting on
much of a quantity order.

Just as an example, when I was working for U.C. we had some Model 33 
machines with typewheels for 1962 ASCII, which had a left-pointing arrow
and an upward-pointing arrow.  Then when 1968 ASCII came out the leftward
arrow was replaced by the underscore, and the upward arrow was replaced by
a caret.  Now maybe I had a special "in" with Teletype, maybe not, but
I talked to one of the sales engineers about this, because there were
some computer languages that used the left and up arrows that we were 
still using.  But we didn't want to perpetuate the old characters either,
since 68 ASCII was coming into use.  So I got him to make me some 
typewheels where the underscore was a sort-of wedge-shaped thing to
suggest both underscore and left arrow, and maybe we took the caret as
OK for the up arrow and there was some other character that we changed
to something suggestive of both the old and new character sets.  And they
made the typewheels for us, even though we probably bought no more than
a dozen machines and probably no other customer had asked for anything
like that.

Also they made machines for computer manufacturers where the code was
scrambled with respect to Murray.  There was a Model 28 printer used
as a console device on the Burroughs 220 computer.  The type box was
all rearranged so that what they sent to the printer was a 5-level version
of 6-bit BCD computer code.  For that matter, there was the famous
late 1930s Bell Labs relay computer that was operated remotely by 
Teletype.  They used Model 26 machines, with a special keyboard
having only digits and a few other keys, and the type arrangement
scrambled to conform to the internal code of the machine.

There was a time when I thought that APL might be the next big thing
in time shared computing, so I was wishing the Model 38 would get out
the door with an APL type cylinder.  By the time Model 38 hit the
streets APL was already past its peak, I think.




-- 

jhhaynes at earthlink dot net