News about Teletypes and similar mechanical teleprinting terminals

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From: Paul Potter <pryan_st@hotmail.com>
Subject: Re: Why putty?

Keith F. Lynch wrote:
>
> Stephen Jones <martians@sdf.lNoOnSePsAtMar.org> wrote:
>>
>> Anyone use real TTYs?  Like this:
>>
>>     http://www.youtube.com/watch?v=Ml00ngVwrcU
>>
>> Now thats a TTY ..
>
> I have no idea what's at that URL.  I read the net on a DEC VT420
> terminal, and it doesn't do video.

I like your old school way of doing it.


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Date: Fri, 22 Feb 2008 01:15:03 +0000 (UTC)
From: Richard <legalize+jeeves@mail.xmission.com>
Subject: Re: sources for Teletypes

John <slawmaster@gmail.com> spake the secret code
<ce8b5a3d-f8f7-4ca5-a869-cfc59298efce@n58g2000hsf.googlegroups.com> thusly:
>
> I'm looking for a ASR 33 or ASR 35 Teletype to put in the office here
> at work... anybody have some recommendations on where to find one?
> San Francisco area is preferable but anywhere is fine.

They come up on eBay periodically and sell for anywhere between a
couple hundred and several thousand dollars, depending on condition
and accessories.

-- 
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
      <http://www.xmission.com/~legalize/book/download/index.html>

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    1996 address listing

    Teletype Corporation
    5555 Touhy Ave.
    Skokie, IL 60077-3235 USA

    Phone: +1 847/677-0800

 ..............................................................................

As of early A.D. 2004, commentary on the Teletype Model ASR33 printing terminal
may be viewed here:

    http://www.pdp8.net/asr33/asr33.shtml

 ..............................................................................

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X-Telecom-Digest: Volume 11, Issue 938, Message 2 of 6
Date: 17 Nov 1991 08:34:46 GMT
From: haynes@cats.UCSC.EDU (Jim Haynes)
Subject: History of Teletypewriter Development

Here's another one (and that exhausts my supply). These two came into
my hands as Monographs when I was working for Teletype in 1963-1966.
The main reason I typed them in is to get them into the telecom
archive since they contain information that isn't readily available so
far as I know.


              HISTORY OF TELETYPEWRITER DEVELOPMENT

			 R. A. Nelson

		     K. M. Lovitt, Editor


October 1963					Teletype Corporation
						5555 West Touhy Avenue
						Skokie, Illinois

			------

		      ABSTRACT

  The success of the modern teletypewriter began with Howard L. Krum's
conception of the start-stop method of synchronization for permutation
code telegraph systems.  The purpose of this paper is to provide a
brief historical account of events which led to that achievement and
of those which ensued.

  Four areas of development will be covered:

  (1) The contributions of Sterling Morton, Charles L. Krum and
      Howard L. Krum.
  (2) The contributions of E. E. Kleinschmidt.
  (3) The contributions of AT&T and Western Electric.
  (4) The contributions of L. M. Potts

			-----

     _HISTORY OF TELETYPEWRITER DEVELOPMENT_

  Area I.  In 1902 a young electrical engineer named Frank Pearne
solicited financial support from Joy Morton, head of the Morton Salt
interests.  Pearne had been experimenting with a printing telegraph
system and needed sponsorship to continue his work.  Morton discussed
the matter with his friend, Charles L. Krum, a distinguished
mechanical engineer and vice president of the Western Cold Storage
Company (which was operated by Joy's brother, Mark Morton).  The
verdict for Pearne was favorable, and he was given laboratory space in
the attic of the Western Cold Storage Company.

  After about a year of unsuccessful experimenting, Pearne lost
interest and decided to enter the teaching field.  Charles Krum
continued the work and by 1906 had developed a promising model.  In
that year his son, Howard, a newly graduated electrical engineer,
plunged into the work alongside his father.  The fruit of these early
efforts was a typebar page printer (Patent No. 888,335; filed August
22, 1903; issued May 19, 1908) and a typewheel printing telegraph
machine (Patent No. 862,402; filed August 6, 1904; issued August 6,
1907).  Neither of these machines used a permutation code.

  They experimented with transmitters as well, applications filed in
1904 and 1906 maturing into Patents No. 929,602 and No. 929,603.
These patents covered modes of transmission which depended both on
alternation of polarity and change in current level.

  By 1908 the Krums were able to test an experimental printer on an
actual telegraph line.  The typing portion of this machine was a
modified Oliver typewriter mounted on a desk with the necessary
relays, contacts, magnets, and interconnecting wires (Patent No.
1,137,146; filed February 4, 1909; issued April 27, 1915). As a result
of the successful test of this printer, Charles and Howard Krum
continued their experiments with a view to developing a direct
keyboard typewheel printer.

  They sought most of all to discover a way of synchronizing
transmitting and receiving units so that they would stay "in step."
It was Howard Krum who worked out the start-stop method of
synchronization (Patent No. 1,286,351; filed May 31, 1910; issued
December 3, 1918).  This achievement, which more than anything else
put printing telegraphy on a practical basis, was first embodied (for
commercial purposes) in the "Green Code" Printer, a typewheel page
printer (Patent No. 1,232,045; filed November 28, 1909;issued July 3,
1917).

  The transmitters first used by the Krums were of the continuously-
moving-tape variety. (A stepped tape feed, they maintained, would have
reduced transmission speed.)  In order to permit sequential sensing,
the rows of code holes were arranged in a slightly oblique pattern
(with respect to tape edges).  This method of transmission is more
fully elaborated in Krum Patents No. 1,326,456, No. 1,360,231, and No.
1,366,812.

  Keyboard-controlled cam-type start-stop permutation code transmitters 
were developed by Charles and Howard Krum in about 1919.  Such a
device is the transmitter component of the Morkrum 11-Type tape printer
(Krum Patent No. 1,635,486).  This kind of transmitter employs a
single contact to open or close the signal line.

  In about 1924 the Morkrum Company introduced the No. 12-Type tape
printer (H. L. Krum Patent No. 1,665,594).  On December 23, 1924,
Howard Krum and Sterling Morton (son of Joy Morton) filed an
application on the 14-Type type-bar tape printer which matured into
Patent No. 1,745,633. [1]

  Area II.  It appears that the early efforts of E. E. Kleinschmidt
were directed toward development of facsimile printing apparatus and
automatic Morse code equipment.  He patented first a Morse keyboard
transmitter (Patent No. 964,372; filed February 7, 1095; issued
January 11, 1910) and later a Morse keyboard perforator (Patents No.
1,045,855, No. 1,085,984, and No. 1,085,985).  (The latter became
known as the Wheatstone Perforator.)

  In 1916 Kleinschmidt filed an application for a type-bar page
printer (Patent No. 1,448,750 issued March 20, 1923).  This printer
utilized Baudot code but was not start-stop.  It was intended for use
on multiplex circuits, and its printing was controlled from a local
segment on a receiving distributor of the sunflower type.  Later,
around 1919, Kleinschmidt appeared to be concerned chiefly with
development of multiplex transmitters for use with this printer
(Kleinschmidt Patent No. 1,460,357).

  It seems that Kleinschmidt first became interested in modern
start-stop permutation code telegraph systems when H. L. Krum's basic
start-stop patent was issued in December 1918.  Shortly after that
Kleinschmidt filed an application entitled "Method of and Apparatus
for Operating Printing Telegraphs" (Patent No. 1,463,136; filed May 1,
1919; issued July 24, 1923).  The system described therein employed
the start-stop principle with a modified version of his earlier
multiplex distributor. That patent, accordingly, was dominated by the
Krum start-stop patent.  The conflict of patent rights between the
Morkrum Company and the Kleinschmidt Electric Company eventually led
to a merger of the two interests.

  Shortly after the new Morkrum-Kleinschmidt Corporation (later called
the Teletype Corporation) had been established, Sterling Morton,
Howard Krum, and E. E. Kleinschmidt filed an application covering the
commercial form of the well-known 15-Type page printer (Patent No.
1,9904,164).  [2]

  Area III.  Teletype entered the Bell System in 1930.  From this
point on, advances in the Teletype product can be considered the
result of the pooled efforts of the AT&T Company, the Western Electric
Company, and the Teletype Corporation.  Teletype Corporation, of
course, holder of the basic patents and expert in the art, was the
chief contributor.

  Although it appears from the report of R. E. Pierce, dated December
24, 1934, that the Bell System was active in the development of
telegraph printers and transmitters as early as the year 1909, a
review of the patents issued to Bell reveals no significant
contribution to modern teletypewriter development (using start-stop
permutation code) until the introduction in 1920 of the 10-A
teletypewriter (Pfannenstiehl Patents No. 1,374,606, No. 1,399,933,
No. 1,426,768, No. 1,623,809, and No. 1,661,012).

  The 10-A teletypewriter was the first embodiment of such basic
design features of the 15-Type printer as stationary platen, moving
type basket, and selector vane assembly, but the majority of
improvements incorporated in the 15-Type were proprietary to the
Teletype Corporation.

  Area IV.  The earliest contribution of Dr. L. M. Potts to the
start-stop method of synchronization appears to have been set forth in
a patent application filed November 18, 1911, covering a reed-type
start-stop selector (Patent No. 1,151,216).

  In 1914, Dr. Potts filed an application for a single magnet page
printer which used an eight-unit code (Patent No. 1,229,202; issued
June 5, 1917).

  In 1915, Dr. Potts filed an application covering another single
magnet page printer, this one using the start-stop permutation code
(Patent No. 1,370,669; assigned to AT&T March 8, 1921).

  Potts Patents No. 1,517,381 and No. 1,570,923 were also assigned to
AT&T.

                           ----------

[1] For anyone who is old enough to have seen a Western Union Telegram
where the typing is on narrow gum-backed tape that is moistened and
stuck to a telegram blank, this is the machine that produces that kind
of printing.  The same mechanism is the basis of a typing reperforator, 
a machine which punches received signals into a tape for retransmission
and also types on the tape so an operator can read it.

[2] This is the machine used until the 1960s or so by the news wire
services.  Some radio stations still use a recording of the sound of
one of these machines as background during news broadcasts.


haynes@cats.ucsc.edu   haynes@cats.bitnet


[Moderator's Note: Thank you for two very excellent articles this
weekend on the history of Teletype and its predecessor companies.
Jim's earlier article on the history of the Morkrum Company was
distributed as a special mailing sent out between issues 936-937 on
Saturday evening. Watch for your copy to arrive if it hasn't yet. 

But I am curious about something not mentioned in either article. Did
the Bell System buy out Morkrum and change the name to Teletype in
1930 or did Teletype start and later buy out Morkrum?  How did that
transition occur? I love these history articles because so much
telecom history happened right here in Chicago -- the Chicago I like
to remember from years ago.  PAT]

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Article 22297 of comp.dcom.telecom:
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From: haynes@cats.UCSC.EDU (Jim Haynes)
Newsgroups: comp.dcom.telecom
Subject: Re: History of Teletypewriter Development
Message-ID: <telecom11.947.7@eecs.nwu.edu>
Date: 19 Nov 1991 06:09:57 GMT
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X-Telecom-Digest: Volume 11, Issue 947, Message 7 of 12

> From cmoore@BRL.MIL Mon Nov 18 08:30:01 1991
> To: Jim Haynes <haynes@cats.UCSC.EDU>

> Among the patents in the message about Teletype is this one:
> 15-Type page printer   1,9904,164 [sic]

> Is there a type of some sort in this patent number?

Yes, there is a typo.  The patent number should be 1,904,164.


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X-Telecom-Digest: Volume 11, Issue 1026, Message 1 of 9
Date: 18 Dec 1991 05:52:32 GMT
From: sjl@glensjl.glenbrook.com (Scott Loftesness)
Subject: AT&T Exits Telegraph Business

[Moderator's Note: The end of an era!  Thanks also to Alan Toscano for
sending this AT&T press release.   PAT]

     BASKING RIDGE, N.J. -- Familiar to the world over through the
clickety-clack of ticker tape machines and teletypewriters, telegraphy
has been gradually bowing out of the telecommunications picture during
the last twenty years.

     The nonstop chatter has been replaced by the hum of laser
printers and the electronic beeps on computer screens.  AT&T, a
leading innovator and major service provider of telegraphy, announced
this year it is withdrawing the service due to the universal
availability of lower-cost, higher quality digital telecommunications
services.

     "The incredible advances in our industry means customers can get
more for less," said Wes Bartlett, AT&T district manager, Business
Communications Services.  "Today's digital technology can transmit
information hundreds of thousands times faster than telegraphy and is
considerably more cost-effective for users.

     "Telegraphy has been to the twentieth century what
state-of-the-art digital telecommunications services will be to the
next century," Bartlett added.  "We are proud of our contributions in
both areas."

     The transmission of telegraph service is based on analog
technology, which sends information by continuous electrical waves.
Today's digital technology breaks information into its smallest
components, the binary "ones and zeros" of computer language.

     However, telegraphy was the actually the first digital service --
although a very simplified version compared with today's technology --
since it was produced on the customer's premises in terms of "on or
off," or "dash or space."  It was converted to analog for transmission.

     Telegraphy usage accelerated rapidly during the 1920s when the
financial industry adopted the technology to send records of
transactions.  At this time, news organizations began using telegraph
service for transmitting stories between offices.

     In November, 1931 the Bell System inaugurated the teletypewriter
exchange service, often called the TWX (pronounced "twicks") service.
It provided a complete communications system for the written word,
including teletypewriters, transmission channels and switchboards.

     Telegraphy was adopted by many kinds of businesses, including
utility companies, alarm companies, airlines, and brokerages as well
as government agencies.  It was used heavily through the 1960s.

     Most of AT&T's telegraph service customers have been converted to
digital private line services such as DATAPHONE (R) Digital Service
and ACCUNET (R) Spectrum of Digital Services.

     "Our name remains American Telephone and Telegraph," Bartlett
said.  "It is an historic name and our legacy.  We are proud to have a
corporate name that spans generations of communications technology.

     "Despite rapid technological change, AT&T remains focused on
helping people communicate," Bartlett added.  "Telegraphy helped bring
us to this point.  Digital technology is taking us into a new era of
global messaging."

                             ### 


                         Background
                              
                WHAT WAS TELEGRAPH SERVICE?

Telegraph service made it possible to communicate large volumes of
information between two or more locations.  Telegraph circuits
permitted customers to send to each other a printed or hard copy
version of the information at reasonable cost, which was impractical
with the telephone.

A telegraph circuit consisted of four components: station equipment
installed on the customer's premises, such as a teletypwriter and
teleprinter; the local loop, or wires, between the customer location
and the AT&T central office; the central office equipment in the AT&T
telegraph serving test center (STC); and the wires connected to the
telegraph STC serving the other customer.

Here's how it worked: Customer A sent information to customer B by
typing the information on a teletypewriter keyboard.  The
teletypewriter converted the message to a coded signal which was sent
out on the local loop to the STC and central office equipment.  There
the signal was converted to make it compatible with the carrier's
lines and sent on to the STC serving the distant city.  The central
office equipment then converted the signal again and sent it over the
local loop to customer B's teletypewriter which decoded the signal and
printed the information.

The procedure was reversed if customer B wanted to send information to
customer A.  This method of sending information, where only one
station could send at a time, was accomplished over a simple
half-duplex, or two-wire circuit.  When both customers wanted to send
and receive at the same time a full-duplex, or four-wire circuit, was
used.

At its peak in 1970, telegraph service could transmit data at 150 bits
per second.

                             ### 


                 AT&T and Telegraph Service

1887:  First private-line telegraph service, for L. H. Taylor 
       & Co., brokers, between their offices in New York and 
       Philadelphia.

1888:  First service for news media customer, Globe Newspaper 
       Company, between New York and Boston.

1915:  Teletype offers speeds of 30 or 50 words per minute.

1920s: Press and financial markets create a boom for usage of 
       the service.

1939:  Speed reaches 75 words per minute.

1944:  Speed reaches 100 words per minute.

1957:  Teleprinter introduces speeds of 300 words per 
       minute.

1970s: Decline in usage begins as electronic data processing 
       replaces many telegraph functions.

1980s: Wireless and digital methods accelerate decline.

1991:  AT&T exits telegraph service.
                              
                             ### 


Scott Loftesness            Internet: sjl@glenbrook.com
515 Buena Vista Avenue      Others: 3801143@mcimail.com 
Redwood City, CA 94061      76703.407@compuserve.com

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X-Telecom-Digest: Volume 13, Issue 149, Message 1 of 5
Date: Tue, 2 Mar 1993 14:26:39 -0800
From: haynes@cats.UCSC.EDU (Jim Haynes)
Subject: A Little More TWX History

Well of course the original TWX goes back to about 1930, used 3-row
machines, and manual switchboards.  In fact the introduction of TWX
was what caused AT&T to buy the Morkrum-Kleinschmidt Corp. and rename
it Teletype.  At the time the service was provided using
telegraph-grade circuits.  You'll occasionally see a picture of an old
TWX switchboard, maybe in an old encyclopedia.  The switchboard
operators used tape-strip printers to communicate with the customers.
Telex was in use in Europe in about the same time frame, and used SXS
switching technology and telegraph-grade circuits.

Western Union introduced Telex to the U.S. in the early 60s.  This was
probably a bad mistake for them.

   1) They had to buy a lot of electromechanical switching equipment
      which was soon to be obsoleted by electronic switching.

   2) AT&T was about to move TWX to the voice switched network, where the
      enormous volume of voice service had driven the cost of connections
      and bandwidth way down.  The telegraph-grade lines were no longer
      cheaper than voice circuits; they were in fact more costly to AT&T.

   3) It put W.U. into practically head-to-head competition with an AT&T
      service; and AT&T was a much stronger company financially.

   4) W.U. was usually dependent on the telephone companies for local loops
      between customers' offices and the nearest W.U. office.  Thus W.U.
      was at the mercy of its competitors rates for these private lines.

As an aside, European Baudot machines tended to have four-row
keyboards.  The digits were on the fourth row, like a typewriter.
There were blocking bars such that if the machine was in FIGS case the
digit keys were unblocked and the corresponding letters keys were
blocked.  So the user still had to send FIGS and LTRS as in the U.S.;
it was just that the European machine design took a slightly different
direction from that in the U.S.

The European machines also tended to have built-in paper tape
facilities of the limited sort that Teletype introduced into the Model
32 and 33 machines.  In previous Teletype designs the paper tape
equipment was mechanically independent of the keyboard and printer.
You could, for instance, be punching a tape from the keyboard at the
same time you were receiving a message on the printer; and you could
be sending from tape at the same time you were punching another tape
from the keyboard.  In the European machines, and later in the
Teletype 32 and 33, the tape punch had some parts in common with the
printer and the tape reader shared some parts with the keyboard.
Hence you couldn't use the keyboard while sending from tape; you
couldn't punch a tape from the keyboard while printing something else,
etc.

The Teletype Model 15 has been mentioned as a heavy-duty machine
dating from 1930.  In the late 1930s some of the Bell companies asked
for a less expensive machine for TWX service, recognizing that a lot
of offices could use TWX but didn't need the heavy-duty machine.  (The
Model 15 is what was used for AP and UP news wires through the 1950s.
It could stand up to the around-the-clock printing that occurs in that
service.)  The answer to this request was the Model 26.  The 26 used a
rotating type cylinder holding individual slugs of type.  The cylinder
stayed in one place and the paper platen moved from side to side as in
a typewriter.  (In the Model 15 and the later machines the paper
platen is stationary and the printing element moves across the page.)

The Bell System phased out the Model 26 machines in, oh, the late 40s
and 50s.  The machine didn't save enough in first cost to be worth
supporting both it and the Model 15 in terms of parts and maintenance
training.  Lots of Model 26 machines wound up in amateur radio
service.  The hams formed organizations to plead with the Bell
companies to sell their used machines to hams rather than breaking
them up (to prevent their falling into the hands of those who would
use them in competition with Bell services).  Hams had to sign a legal
form to the effect that they would not use the machine outside the
hobby, and would not sell it to anyone without requiring a similar
promise.

In the late 50s and early 60s came all the work that resulted in ASCII
 -- first the upper-case-only 1961 ASCII and then the up/low 1968
ASCII.  Prior to ASCII there were lots of codes floating around.
Teletype made the Model 29, which was an eight-level four-row machine
working on one of the IBM BCD codes.  I believe this was used only
internally in Western Electric; AT&T was scared to put an IBM coded
machine out to the public lest non-IBM computer makers complain that
the AT&T giant was favoring the IBM giant at their expense.  The Model
35 was based on the 29; in fact I'm aware of some people converting 29
printers to ASCII by changing just a few parts.  Many parts were
common between the five-level Model 28 and the eight-level Model 35.

The Model 32 and 33 machines actually started as a project to develop
a light-weight machine for the military.  The light-weight project
didn't get very far; but a lot of the ideas wound up being used in the
low-cost printer project.  Again the Bell companies and Western Union
saw a need for a machine that would cost a lot less than the
heavy-duty machines, for use in offices that didn't have a lot of
traffic.  I might mention that Western Union dabbled in making its own
teleprinters from time to time; occasionally one will see a sample of
their Model 100 family.  I believe W.U. was the main customer for the
32, for Telex service and the Bell companies were seen to be the main
customers for the 33 for the new four-row dial TWX service.  These
machines had most of the parts in common.  They were available with
and without paper tape; where paper tape was present it followed the
European style, so you couldn't do all the things with these machines
that you could with a 28 or 35.

The design objective for the 32 and 33 was that they would be used on
an average two hours per day.  Cost was held down by not heat treating
and hardening and nickel plating the parts; some adjustments were made
by bending parts rather than by moving parts on elongated holes and
that sort of thing; assembly was designed for high volume with a die
cast base and self-tapping screws and parts that snapped together
without bolting.  Meanwhile along came the minicomputer companies who
adopted the 33 as a console device, where it often ran around the
clock (and generated a lot of cursing about the frequent need for
maintenance).

For manual TWX Teletype supplied a basic machine to the phone company,
which added some kind of Western Electric box on the wall for line
interface.  This might be a carrier channel terminal or some relays
for a D.C. line; and there were schemes where ringing was used to
control the motor on the Teletype machine, and schemes for cutting off
current in the line when it was not in use.  Telex and dial TWX
required additional components for setting up and controlling the
call.  The Model 32 for Telex had a built-in Call Control Unit with a
dial and line relays, all ready to connect to the D.C. local loop.
For dial TWX there was a Western Electric modem stashed in the
Teletype stand and a variety of call control units (pulse dial, tone
dial, card dialer, loudspeaker vs. earphone, etc.)  made by Teletype
and connecting to the modem.  This was a source of considerable
annoyance to Teletype, as the interface involved 99 wires, each of
which was negotiated between the modem designers at Bell Labs and the
call control unit designers at Teletype.  A little later some of the
Bell companies would save money by furnishing a Bell modem with
built-in telephone connecting over a few-wire cable to a Teletype
private-line-version machine having no call control unit.

There is a lot of weird and interesting (perhaps) lore connected with
the modems.  Since dial TWX used a voice-bandwidth connection they
could afford the luxury of full duplex modems using two different
frequency pairs for the two directions of transmission.  This
introduced the complexity that a modem had to know whether it was
originating or answering a call to know which pair of frequencies to
use for which purpose.  Even after Bell began supplying modems for
connection of customer-provided data equpment (just before Carterfone)
these modems could function in either originating or answering roles.
After Carterfone the suppliers of modems for computer time sharing
could take advantage of the fact that the terminal always originated
and the computer always answered; so we got reduced cost
originate-only and answer-only modems.

It always seemed to me that the TWX section of Bell Labs was
controlled by old geezers who had been around since 1930 and couldn't
imagine that a TWX machine would ever want to talk to anything except
another TWX machine.  If you wanted to use the same kind of Teletype
machine to talk to a computer, well that was another matter entirely.
The modems had separate originate and answer frequency pairs, each
binary FSK.  This permitted two options for which frequency pair would
be originate and which would be answer, and four possiblities (two for
each pair) of which frequency would be mark and which would be space.
Thus it was possible by wiring options to set modems up for as many as
eight mutually-incompatible services, all using the same voice
switched network without any restrictions on area codes and numbers.
I remember hearing about TWX, and TWX-prime, and WADS (wide area data
service) and WADS-prime, all of which were to use the same modems and
switched network without any of these being able to communicate
outside its own service.  I guess they had in mind different tariffs
for TWX machines talking to TWX machines versus terminals talking to
computers, versus some other things.  Practically all of this was
swept away by Carterfone.


 //////////////////////////////////////////////////////////////////////////////


Newsgroups: comp.dcom.telecom
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X-Telecom-Digest: Volume 13, Issue 151, Message 13 of 14
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Date: Wed, 03 Mar 1993 20:00:48 GMT
From: hhallika@tuba.calpoly.edu (Harold Hallikainen)
Subject: Re: A Little More TWX History

	Thanks for the interesting history of Teletypewriters!  Back
in high school I used a model 15 with model 14 tape "typing reperf"
and "transmitter distributor" on amateur radio.  A friend and I also
set up a local teletype network.  We ran about a mile and a half of
single conductor wire through the trees of the neigborhood.  We then
fed this wire against ground, running a 60 mA current loop.  We made a
motor control circuit for each end.  When I wanted to leave a message
on his machine, I'd supply loop current, which would start both
motors.  To shut down, I'd drop my loop power supply which would cause
both machines to "run open" for a while, 'til a capacitor across a
current sense relay discharged, shutting down the AC to the motor.

	I also remember the very complicated wiring inside the model
15.  There was a huge wiring harness that seemed to allow for infinite
options.  I finally ripped it all out and brought out six wires.  Two
for the keyboard, two for the "selector magnets" (series for holding
magnets at 60 mA, parallel for pulling magnets at 60 mA, or series for
holding magnets at 20 mA), and two for AC power to the motor.

	The previous article spoke of various codes used on Teletypes.
I recall seeing machines that LOOKED like model 15s, but used a six
level code.  These were used by press wire services.  The sixth bit
allowed for upper and lower case.  At my college newspaper, they had
one of these printers and a tape punch running all the time.  When the
editor found an article of interest, he/she would go searching through
the punched tape looking for the article.  Articles were identified by
a number that was punched to be readable in the holes on the tape (and
garbage on the printer).  This tape was then sent to mechanical
Linotype machine where the article was cast in lead.  They'd then pull
a proof from the lead type, put it in the paste-up for the page.  Then
they'd photograph the page, make offset plates and print the paper.
Watching that Lintotype cast the type to be used just once was pretty
amazing!

	The previous article also mentioned the use of model 15s in
radio and TV station wire service use in the 1950s.  Here in SLO Town,
they were used through the mid 1970s.  These were eventually replaced
with Extel dot matrix printers, the first dot matrix printer I ever
saw.

	Finally, I still have a model 33 with tape punch, reader and
internal Bell 103 modem sitting back in a corner here.  When I got it,
I was thinking of taking info out of our old CP/M PC board CAD system
and generating drill tapes for the PC house.  The machine is still
sitting in the corner.  We now don't even plot our boards.  We just
take a disk with the Gerber photoplot file and drill file across town
to the PC house.  We give them a disk and back come PC boards.  Pretty
neat!

	It's amazing to see the changes I've seen in the electronics
industry ... but then, I'm getting older ...


Harold Hallikainen              ap621@Cleveland.Freenet.edu
Hallikainen & Friends, Inc.     hhallika@oboe.calpoly.edu
141 Suburban Road, Bldg E4      phone 805 541 0200 fax 544 6715
San Luis Obispo, CA 93401-7590  telex 4932775 HFI UI

 //////////////////////////////////////////////////////////////////////////////

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X-Telecom-Digest: Volume 13, Issue 300, Message 1 of 10
Lines: 160
Date: 3 May 1993 10:24:18 GMT
From: Jonathan_Welch <JHWELCH@ecs.umass.EDU>
Subject: History of Mark and Space

Pat, I thought the following article might be worth reposting in
TELECOM Digest.  The original message was posted into a notes
conference on a vax DECUS members may subscribe to.  Once a month
tidbits from various notes conferences are reposted to the outside
world.


Jonathan Welch  VAX Systems Manager  Umass/Amherst  JHWELCH@ecs.umass.edu

                              -----------
DECUServe Journal, May, 1993   Beginning at page 15
(09/22/90 Harvey:  Mark and Space)

    "Mark" and "space" are curious terms to find in a hardware topic
discussing data communication.  They seem more appropriate for the
Windows conference.  But they are truly electrical communication
terminology and have many related forms, such as "steady mark",
"continuous spacing" and a seemingly unrelated term: "running open".
 
   I thought their origin might be of interest and along the way,
we'll discover where that curious "break" key came from that many of
us have on our keyboards and these days often use to get the attention
of the terminal server.

    These terms are very old and originated with an early graphical
device.  People never think of the telegraph as graphical
communication, but that's the way it was originally conceived.  Our
impression of the telegraph comes largely from movie stories of times
a century ago, when telegraph operators listened to the strange ticks,
tocks and rattles from the telegraph sounder and converted them into
urgent messages that pushed the plot forward.

    Morse didn't invent it that way.  His original device was an
electromagnet that pulled a pen (possibly a quill) against a moving
strip of paper.  When current flowed through the electromagnet, the
pen touched the moving paper and made a mark.  When the current was
off, a spring retracted the pen and there was a space on the paper.
Short marks were called dots.  Long marks were called dashes.

    Now this explanation is so simple and pat, it just has to be
largely legend and over-simplification.  There were many different
schemes, such as keeping the pen in contact with the paper and moving
it sideways by the electromagnet.  But the mark/space concept seems to
have stuck, because it appears in very early communication literature.

    This graphical device was actually used in production communi-
cation for a while. Some of the operators of the machines found that
they could recognize the "call letters" of their telegraph office when
the electromagnet and pen started tapping out a message on the strip
of paper.

    If the message was for another office, they didn't need to get up
to see if the message was for them.  Soon, they were able to just
write the message down on the telegraph form as it came in without
needing to "read" the tape.  When the operators were able to fully
"read" Morse code with their ears, they could stop putting ink in the
pen.  The telegraph sounder was born.
 
   You couldn't see the marks and the spaces between them anymore, but
they were still there in the minds of the engineers designing
telegraph systems.
 
   For good electrical engineering reasons, telegraph offices were
wired in series.  At one end of the railroad (for example) there was a
powerful battery with one pole connected to a rail and the other
connected to a wire that ran on posts for the length of the railway,
where it was also connected to the rail.  This constituted a simple
series circuit with the battery current flowing through the wire, into
the rail at the far end, and back through the rail to the battery.
 
   At each telegraph office along the line, the wire was cut, brought
into the office, sent through the coil of the electromagnet of the
sounder, then through the telegraph key, then back up to the pole and
on down the line to the next office.

    But you may have noticed a problem.  The telegraph key is normally
an open circuit.  When the operator pressed down on the key, the
circuit was closed and the current flowed.  How, then, did the current
flow when everything was hooked in series and all those keys were open
circuits?

    If you've ever looked closely at a real telegraph key, you may
have noticedthat it has a knife switch build into it, and that switch
is arranged to short the contacts of the key.  When the operator was
not actually sending a message, he or she (many early telegraph
operators were women) would close the knife switch so that the key
contacts were shorted and the whole series circuit was unbroken.
 
    Thus the normal idle telegraph line was in a "steady mark"
condition - a current flowed through all the sounders which if the pen
was still there would have caused a mark to be made on the moving
strip of paper.  The knife switch on each telegraph key was perhaps
the first "push to talk" button.  The operator had to "open" the knife
and break the circuit so the key could turn the current on and off and
send a message.
 
   Not surprisingly, this knife was called the break switch. When an
operator opened the knife the current stopped flowing in all the
sounder electromagnets and they went tock.  Everyone up and down the
line knew someone was about to start sending a message. The break
switch alerted them.

    When the Indians cut the telegraph wire, the circuit was open and
all the sounders went tock.  "Open" meant trouble.

    The graphical device didn't disappear, however.  The interest in
having the message automatically recorded on paper that could be read
without having to learn the arcane art of "reading" Morse code by ear
remained.  The inventors worked to improve on the simple marks
separated by spaces and actually make letters and figures appear.
 
    One early attempt was the telautograph.  It attempted to servo the
up/down and sideways movements of a pen being used to write a message
in longhand to a remote pen reproducing the motion and hence
re-creating the longhand.  It worked well for very short distances but
they didn't have the technology to send the control signals useful
distances.  There were other schemes using many wires.  Expensive.

    The big winner was the stock ticker.  It was the ancestor of all
the various asynchronous communication gadgets we have today.  It was
a triumph of mechanical ingenuity that enabled an ordinary telegraph
wire (and there were many) to be converted to actually print a message
in letters and figures on that moving strip of paper.  You didn't need
an expensive telegraph operator hanging around to "read" Morse and you
didn't have to puzzle out the strange patterns of marks and spaces.
But the communication technology was telegraph and the marks and
spaces were still there in the minds of the engineers.

    The stock ticker used the same series circuit technology of the
telegraph.  The wire ran from the floor of the exchange to the nearest
broker's office, through an electromagnet in the ticker machine, and
then on to the next office.  And yes, if the Indians (or a cleaning
lady) broke the wire anywhere, all the tickers went dead.

    Dead?  No, they went crazy.  The continuous telegraph current when
there were no stock trades being reported kept the ticker mechanisms
idle.  Steady mark.  Good.  The start of a trade message was a break
in the circuit (start pulse) which caused the ticker mechanism to
start spinning.  The following sequence of marks and spaces caused the
mechanism to select a particular character on its wheel and a hammer
struck the paper strip against it.

    When the circuit was broken by the cleaning lady, it was in a
"continuous space" condition, causing all the ticker machines to spin
their clockwork, "running open" until someone fixed the break. These
terms stayed with communication technology to the first minicomputers.
The venerable ASR 33 Teletype, one of the foundation stones of the
minicomputer industry, used telegraph series current loop technology,
marks and spaces, and "ran open" when you disconnected it from the
PDP-5.

    Well, if you got this far, you're probably wanting to know about
where your break key came from if you haven't figured it out already.
Yep, it's that knife switch on the side of the telegraph key.  You
didn't know you're a telegrapher, did you?


[Moderator's Note: Thank you for passing along a fascinating story. PAT]

 //////////////////////////////////////////////////////////////////////////////

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Date: 16 Sep 1993 15:15:16 GMT
From: daveb@jaws (David Breneman)
Subject: Re: ASR33 info needed

Steve Willoughby (steve@aardvark.rain.com) wrote:
:
: I have a pair of old ASR33 teletypes I'd like to get hooked up to my
: computer system, but they don't appear to be using the kind of 
: interface I need.  The teletypes were once used at Western Union,
: and have something called a "polar adaptor" built in.  I'm not sure
: what a "polar" interface is or how it relates to EIA RS232 or 20mA
: current loop.  Maybe polar is something Western Union did on their
: equipment, or maybe it's more common with other ASR33's?

I'm a little rusty, but here goes...

It's the *standard local* interface for teletypes.  The signal is
modulated by reversing the phase (I believe) of the current that
connects the teletypes; that's where the "bipolar" comes from.
That current is sent to the distributor (just like a car ignition,
but in reverse :-)  )  which breaks it into individual bits, the current
from which moves the bars under the keyboard that determine which
character will either be typed on the page or punched on the tape.
It's the Stop Bit, of RS232 fame, that keeps the distributors in the
sending and receiving teletypes in sync.

Teletypes that were used in dialup applications had a big 110-baud
modem in the base (same tones as 300 baud) and can be connected to a
computer by a similar modem on the computer end.  As I recall, if
the machine you're calling has a 300-baud modem running a 110-baud
getty, you can log in (it's been a few years since I've done this,
but I *have* done it).  As far as *directly* wiring a teletype to a
computer a la RS232 or 20mA, you're going to need some kind of
conversion box for that, too.

: Anyway, I have a set of schematics to the terminals and don't mind
: poking around at them to get them to work, but I don't know enough
: about this older technology.  The interface cable leading out of the
: terminal (from the polar adapter) has a ground, send, and receive wire
: rather than the four wires I'd expect with 20mA.

Yes.  And if you try to connect it to anything like a modem or
RS232 port, you'll fry it.  I think it's about 60 volts going
through there (enough current to unlatch the distributor clutch
solenoid at the start of each byte)!  We're talking industrial
data terminal equipment here!  :-)

: Anyone know how to modify such a machine to work with 20mA or RS232?
: Anyone even know what this "polar" interface is or how it works?

I don't.  I've got two ASR33's with the modem base and I've used
one of them to log into a 3B2 a few years ago, but I never tried
to re-wire it to do anything else.  Check in the ham radio group(s).
There's bound to be some RTTY (radio teletype) veterans hanging
around in there.  Those guys modified ASR33s and the older *big*
baudot teletypes to talk over short wave.  If anybody would know,
they would.  (BTW, there was a model of the ???33 which used Baudot
6-bit 66 baud like the older teletypes.  Those won't work as a
data terminal.)

You're best bet might be to find another 33 which is mechanically
dead but has a good modem, make one good one and log in that way.
I've got two ARS33 manuals kicking around - if there's more info
you need I can photocopy the relevant section(s).  Drop me a line
if I can help.

--
David Breneman                        Email: daveb@jaws.engineering.dgtl.com
System Administrator,                 Voice: 206 881-7544  Fax: 206 556-8033
Software Engineering Services
Digital Systems International, Inc.        Redmond, Washington,  U. S. o' A.

 //////////////////////////////////////////////////////////////////////////////

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Keywords: ASR33 TTY help western union
Date: 16 Sep 1993 10:40 PST
From: shoppa@almach.caltech.edu (Timothy D. Shoppa x4256)
Subject: Re: ASR33 info needed
Summary: Need to know how to interface ASR33 to system


In article <CDEIys.6LK@aardvark.rain.com>,
steve@aardvark.rain.com (Steve Willoughby) writes...
>
>I have a pair of old ASR33 teletypes I'd like to get hooked up to my
>computer system, but they don't appear to be using the kind of 
>interface I need.  The teletypes were once used at Western Union,
>and have something called a "polar adaptor" built in.  I'm not sure
>what a "polar" interface is or how it relates to EIA RS232 or 20mA
>current loop.  Maybe polar is something Western Union did on their
>equipment, or maybe it's more common with other ASR33's?
> 

I had a ASR33 teletype hooked to my S100 system a long, long, time ago.
The ASR33 had been used for Telex at a local company before they switched
to something a little more modern.  It also had this "polar adaptor" on
it when I got it.  Luckily, I also got the manual set for the ASR33 with
it, and it was clear enough how to convert back to 20mA current loop.
If you don't get any other replies, let me know and I'll hunt down my 
ASR33 manual set for you (it's 2000 miles away at the moment, so it'll take
a while!)

If I remember correctly, the idea behind the "polar adaptor" was that
if you had a long circuit, possibly with many relays in the circuit to
"repeat" the signal, you ran into a problem if the relay was only
"on" and "off": most relays take a different amount of time to turn on and
off.  Thus you can end up with distorted bits getting passed around, as the
effective delay for the "rise" part was different than the effective delay
for the "fall" part.  The polar relay got around this by making things more
symmetrical; I don't remember the details, but I believe a current flowing
one way meant a mark, and the reverse current meant a space.  These currents
triggered the beast known as the "polar relay", the innards of which I don't
have much knowledge of.

You might try looking in an older ARRL (Amateur Radio Relay League) Handbook,
from the mid-70's or so.  Ham radio operators have for a long time been taking
old teletype equipment for use on radioteletype.  Usually the equipment was
Baudot, not ASCII, but I believe that polar relays could also used in the
Baudot equipment as well.  The Handbook explained the polar relay concept a
little more clearly than I have done.  There was also another ARRL publication,
"Specialized Communication Techniques", which was supposed to discuss
radioteletype equipment in a little more detail than the Handbook.
Nearly all public libraries have back editions of the ARRL Handbook.

>Anyway, I have a set of schematics to the terminals and don't mind
>poking around at them to get them to work, but I don't know enough
>about this older technology.  The interface cable leading out of the
>terminal (from the polar adapter) has a ground, send, and receive wire
>rather than the four wires I'd expect with 20mA.

I believe that if you hook a scope up to the "send" line and type some
characters on the keyboard, you'll see positive-negative voltage swings
corresponding to marks and spaces.  I can't remember exactly what the swings
are, though; probably of the order 50-60 volts on an open circuit.

Hooking the "send" line to the "receive" line will probably give you
local loopback, if you want to play around.

> 
>Anyone know how to modify such a machine to work with 20mA or RS232?

I believe you can get inside and get to the 20mA loop part quite easily.
(Or were ASR33's 60mA loop?  No, I think 60mA was only on the older
Baudot equipment, but I could be wrong.)  At least that was the case on mine;
but on mine it was pretty clear the the polar relay was not part of the
original equipment.

				Tim (KA0BTD) (shoppa@almach.caltech.edu)

 //////////////////////////////////////////////////////////////////////////////


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Lines: 21
Date: Fri, 17 Sep 1993 07:31:46 GMT
From: dchou@NCoast.ORG (David Chou)
Subject: Re: ASR33 info needed

Back in 1976 or so, I actually bought an ASR-33 (brand new) from Teletype
Corporation and converted it to RS-232 use.  As the previous posters have
mentioned, there are a number of configurations.  The basic unit consisted
of a current loop unit, usually defaulting to 20ma, but I do remember that
you could change a jumper to get 60ma current loop.  The output of the
system is between 60-80 volts off the current loop, so it can do a good
job of blowing things on solid state 5 v circuits being used today.  It
is also possible to wire the circuits to that the tty would source the
current or the user could provide an external source.  I think that I
used the latter option.  I remember building a current loop to RS-232 
convertor using some 741 op amps and a +/-12 volt supply using junk from
Radio Shack (shudder).  The ASR-33 sits behind me collecting dust.  The
manuals provided by TTY are very complete, but are somewhat difficult to
decipher.  It would take me some time to decipher what I have done, but
if anyone needs help and is willing to wait, please ask.

Incidentally, I love those mechanical clunkers, but the noise was over-
whelming and the speed was underwhelming!

Dave

 //////////////////////////////////////////////////////////////////////////////

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From: ard@siva.bris.ac.uk (PDP11 Hacker .....)
Subject: Re: ASR33 info needed
Summary: Need to know how to interface ASR33 to system

In article <CDEIys.6LK@aardvark.rain.com>,
 steve@aardvark.rain.com (Steve Willoughby) writes...
>
> I have a pair of old ASR33 teletypes I'd like to get hooked up to my
> computer system, but they don't appear to be using the kind of 
> interface I need.  The teletypes were once used at Western Union,
> and have something called a "polar adaptor" built in.  I'm not sure
> what a "polar" interface is or how it relates to EIA RS232 or 20mA
> current loop.  Maybe polar is something Western Union did on their
> equipment, or maybe it's more common with other ASR33's?

Can't help that much but it gets a mention in the ASR33 service manual volume 1
(which unfortunately does not contain a schematic). However, it appears that
the transmit and receive circuits both use mercury-contact relays that are
sensitive to the direction of current flow through the coils (the polar part).
The transmit output seems to be the contact set (SPCO) of one of these relays,
connected to a +/- 120V supply (but with links to use an external PSU). The
receive input is the coil of such a relay, and requires similar voltages. So,
it looks like a high-voltage RS232-type interface.

> 
>Anyway, I have a set of schematics to the terminals and don't mind
>poking around at them to get them to work, but I don't know enough
>about this older technology.  The interface cable leading out of the
>terminal (from the polar adapter) has a ground, send, and receive wire
>rather than the four wires I'd expect with 20mA.

It's a voltage interface, so 3 wires, Tx, Rx and common ground. In England (and
probably elsewhere), telex systems used an 80V line, which may well be similar.

> 
>Anyone know how to modify such a machine to work with 20mA or RS232?
>Anyone even know what this "polar" interface is or how it works?

Try digging for the 'private line call control unit' - that was 20mA I think.
Otherwise, transmit (from ASR -> computer) should be possible by reducing the
PSU voltage on the relay contacts to +/- 12V, and calling it RS232. Receive may
need a relay swap, or a bit of hacking to the circuitry to get an RS232 level
to switch the existing relay

If you blow up your computer, it's not my fault :-) (Note, you'll not blow up
the ASR33)

> 
>Thanks,
>steve
>-- 
>Steve Willoughby N7PFJ  | "Bart, don't use the Touch of Death on your sister!"
>steve@Aardvark.Rain.Com |                             --Marge Simpson
>                        |---------------------------------------------------
-tony

 //////////////////////////////////////////////////////////////////////////////

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References: <RJM.95Oct4163457@swift.eng.ox.ac.uk>
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Date: 8 Oct 1995 13:23:52 -0400
From: wilsonj@alum01.its.rpi.edu (John Wilson)
Subject: Re: Teletype 43 teleprinter (KSR) ribbons

In article <RJM.95Oct4163457@swift.eng.ox.ac.uk>,
Bob Manners <rjm@swift.eng.ox.ac.uk> wrote:
>I wonder if anyone out there knows of a source for ribbons for the KSR
>43?

I don't know the 43, are these the same little spool ribbons used on other
TTYs like the 33?  If so, they had them in stock at our local Office Max
a couple of weeks ago, I was amazed!  I think it was made by Pelican (or
is that Pelikan), the model 33 wasn't specifically listed but a few other
TTY models were, and scads of other brands, ASR33s supposedly use the same
ribbon as the old Underwoods too so you might try a typewriter store if
they still exist in your area.  It fit perfectly, although it was a little
dry.  If the 43 takes some weird cartridge thing then never mind, I have
no idea what I'm talking about.

The LA120 ribbon appears to be the same width, if you really hate yourself
you could thread part of one onto your old spools, I don't know what you'd
use for the reversing rivets though.

Also discovered:  soaking an ASR33 type cylinder in a carburetor cleaning
bath does a nice job of getting all the gunk out so your O's don't come out
as disks...

John Wilson

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Newsgroups: vmsnet.pdp-11,alt.sys.pdp11
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      !shoppa
Organization: Kellogg Radiation Lab, Caltech
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References: <RJM.95Oct4163457@swift.eng.ox.ac.uk>
NNTP-Posting-Host: altair.krl.caltech.edu
Date: 10 Oct 1995 02:09:47 GMT
From: shoppa@altair.krl.caltech.edu (Tim Shoppa)
Subject: Re: Teletype 43 teleprinter (KSR) ribbons

In article <RJM.95Oct4163457@swift.eng.ox.ac.uk>,
Bob Manners <rjm@swift.eng.ox.ac.uk> wrote:
>
>I wonder if anyone out there knows of a source for ribbons for the KSR
>43? I've had no luck with the local suppliers, Inmac et. al.

My Inmac catalog (Summer '95 Vol 1016M) lists model 43 ribbons, minimum
order 6, at $7.94 each.  Part number H6445.  They also have Model 33
ribbons (also available at any five-and-dime as regular typewriter
ribbons) at $2.78 each, part number H6143.  Their 1-800 number is plastered
all over the catalog (1-800-972-3210), but I can't find any trace
of a regular number for people out of the states.  

Inmac no longer appears to carry 8.5" paper rolls (with sprocket holes
at approx. 8" spacing), as are used on my model 33's.

Interestingly enough, the picture of the Wright-line type storage
cabinet (p. 87 in my Inmac catalog) still shows RK05-type cartridges (on
a cartridge rack), RP06-type cartridges, and RM03-type cartridges
(these are on a shelf).  Not too long ago you could buy these cartridges
new from Inmac.  They're still available from DECdirect, BTW.
(Last time I checked, RK05's were about $135 each, RP06's were about
$1000 each, and RM03's were $255.  RL02's are about $200, I think.)

Tim. (shoppa@altair.krl.caltech.edu)

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Newsgroups: vmsnet.pdp-11,alt.sys.pdp11
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Message-ID: <45g7n7$39j@lyra.csx.cam.ac.uk>
References: <RJM.95Oct4163457@swift.eng.ox.ac.uk>
 <4591f8$19no@alum01.its.rpi.edu>
Organization: University of Cambridge, England
NNTP-Posting-Host: tw500.eng.cam.ac.uk
Lines: 33
Date: 11 Oct 1995 10:53:27 GMT
From: ard12@eng.cam.ac.uk (A.R. Duell)
Subject: Re: Teletype 43 teleprinter (KSR) ribbons

wilsonj@alum01.its.rpi.edu (John Wilson) writes:

>In article <RJM.95Oct4163457@swift.eng.ox.ac.uk>,
>Bob Manners <rjm@swift.eng.ox.ac.uk> wrote:
>>I wonder if anyone out there knows of a source for ribbons for the KSR
>>43?

>I don't know the 43, are these the same little spool ribbons used on other
>TTYs like the 33?  If so, they had them in stock at our local Office Max

Alas the KSR43 takes a very odd cartridge. It's held down by a magnetic 
catch on the right side of the printer chassis, and the ribbon is 
threaded round a set of one-way rollers on the chassis and carriage that 
advance the ribbon when the carriage moves.

>a couple of weeks ago, I was amazed!  I think it was made by Pelican (or
>is that Pelikan), the model 33 wasn't specifically listed but a few other
>TTY models were, and scads of other brands, ASR33s supposedly use the same

I will look out for that. I still run an ASR33. And, of course the same 
ribbon fits the Microline 80 and some old commodore printers.

>Also discovered:  soaking an ASR33 type cylinder in a carburetor cleaning
>bath does a nice job of getting all the gunk out so your O's don't come out
>as disks...

I'll try that as well. Cleaning the type cylinder is not that trivial on 
any machine, but it's worth doing...

>John Wilson

-tony

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NNTP-Posting-Host: alum01.its.rpi.edu
Date: 18 Oct 1995 16:00:38 -0400
From: wilsonj@alum01.its.rpi.edu (John Wilson)
Subject: TTY ribbons

It's amazing how fast articles expire on this server...  Well sorry to bug
the newsgroup with this but a short while ago someone was looking for
ribbons for some TTY model I'm not familiar with, I think it was model 43.
If so, there's an entry in the Global catalog for "Teletype 43 W/Clip",
whatever that means.  Part # is KC2316, price is $6.75.  They also list the
model 14 (presumably they're referring to the 14TR since the other 14s don't
type anything!) but not the myriad of other TTYs that take the same ribbon,
so they may be insane.  Anyway their phone # is 1-800-8GLOBAL, they don't
mention whether they accept international orders but their NE warehouse is
+1-516-625-6200, give it a shot.  If it wasn't a model 43 or the Clip is
important, then never mind, as I say the article has evaporated here.

John Wilson


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Newsgroups: alt.sys.pdp8
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From: ard12@eng.cam.ac.uk (A.R. Duell)
Subject: Re: PDP-8/e and 33s
Date: 3 May 1996 09:48:14 GMT
Organization: University of Cambridge, England
Lines: 37
Message-ID: <4mckou$7ar@lyra.csx.cam.ac.uk>
References: <4m7gmc$8dn@tlaltec.tezcat.com>
            <8BFD080.0BBF000076.uuout@compudata.com>


david.razler@compudata.com (DAVID RAZLER) writes:
>
> Technically (by Teletype maintenance manuals) the "upper cylinder" is a 
> dashpot, a mechanism that dampens the inertia of the print head after a 
> carriage return by trapping air against the cylinder on the print head 
> and the receiver attached to the main portion of the frame.

I know that dashpot well (having had to set up the air hole adjustment on 
it), but I've never heard it called the 'upper cylinder' I will have to 
check in the partsbook...


> Teletype Corp. used this technology at least from the 10-series machines 
> through the 34/5 series.

> The exact amount of air to trap to get each line to line up with those 
> above and below is determined by either long experience or a technology 
> so advanced that it is indistinguishable from magic.

There is an adjustment on the side that affects the time it takes for the 
air to escape, and hence the carriage return time. You have to set it so 
that the carriage returns correctly in one character time, but doesn't 
bounce. I am told that the correct setting depends on the altitude that 
the machine is installed at :-)


> I've never tried improving the seal with STP, though I have seen use of 
> Vaseline on 'newer' Teletypes which used a plastic piston head. (I just 

The older '33s seem to have a metal piston with a rubber insert in it 
(which seems to be a damper, rather than a seal.)>

-- 
-tony
ard12@eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: alt.folklore.computers
Message-ID: <5humn0$ped@lyra.csx.cam.ac.uk>
Date: 2 Apr 1997 22:30:56 GMT
From: "A.R. Duell" <ard12@eng.cam.ac.uk>
Subject: Re: Modems invented?

Robert Billing <unclebob@tnglwood.demon.co.uk> writes:

>In article <5hctit$elp@netaxs.com> hancock4@bbs.cpcn.com "Lisa or Jeff"
writes:
>> Any details about that early service would be appreciated.  Thanks.


> You may also be interested in the box which was supplied by Post
>Office Telephones (now BT) for early dial-up connections in the late
>60s and early 70s. The box was about the size of a modern PC desktop
>case, and IIRC provided full duplex at 110 baud for a Teletype ASR33.

You may be thinking of a Modem 2B. That's a brown and grey metal box about
15" square and 7" high, containing 4 plug-in modules (PSU, modulator,
demodulator, control). It's all discrete transistors, of course.

I beleive the demodulator mixed the incoming carrier with a local
oscillator, took the sum frequency, filtered it (with a chain of LC
filters in a tobacco-tin sized box), and the used a standard FM detector
on the output. Amazingly it works.

The 2B is good to 300 baud, AFAIK, and mine uses a standard RS232
interface, correctly implemented.

> Dialling was by an ordinary rotary dial phone, and a button on the
>phone switched the line over to the modem when you heard carrier.

The most amazing GPO modem I ever saw is the 13A.  This is a complete 300
baud modem in a 1" high plinth that's screwed to the bottom of a modified
type 746 'phone. There's a 'voice' and 'data' button on the 'phone, and a
4 core cable coming out of the pinth ending in a DB25-S RS232 connector
(TxD, RxD, SG, CD are the signals, I think). It uses some metal-can IC's,
and a lot of pot-core inductors.

-- 
-tony
ard12@eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill


 //////////////////////////////////////////////////////////////////////////////

Message-ID: <5i1aop$bpj@tor-nn1-hb0.netcom.ca>
Date: Thu, 03 Apr 1997 22:20:40 GMT
From: John Savard <seward@netcom.ca>
Newsgroups: alt.folklore.computers
Subject: Re: origins of '\' (backslash) on keyboards?

snorwood@nyx10.cs.du.edu (Scott Norwood) wrote:

>I remember reading with interest the thread on the origins of the '\'
>as a directory separator for M$-DOS (as opposed to the '/' used in UNIX).

>Now, here's another question:  at what point did the backslash key
>become standard for computer keyboards?

Well, back in 1964, when the original ASR-33 Teletype was produced--
when ASCII was invented, in other words--the backslash was part of
the character set.

Back then, the caret was instead an up arrow (which it should have
remained, being useful as an exponentiation operator);
the underscore was an arrow pointing left;

and there were no lowercase characters; ` { | } and ~ did not exist
yet. However, in addition to DEL, the last few characters before it
were controls as well: ACK, ESC, and ALT MODE then are now printing
characters, and a different control character is used for ESC.

The last 8 of the first 32 characters did not have their present
meanings; they were just S0 through S7.

John Savard


 //////////////////////////////////////////////////////////////////////////////

Newsgroups: alt.folklore.computers
Date: Thu, 03 Apr 1997 22:23:33 GMT
Message-ID: <5i1au5$bpj@tor-nn1-hb0.netcom.ca>
From: John Savard <seward@netcom.ca>
Subject: Re: origins of '\' (backslash) on keyboards?

In <3340bb0f.65034735@news.sci.fi>, keinanen@sci.fi (Paul Keindnen) wrote:
>
> While strictly speaking ASCII is a purely US standard, many national
> 7-bit character sets exist in the rest of the world, which are almost
> identical to the ASCII character set, but a few character positions
> are reserved for national variations.

Yes, and these character sets belong to International Telegraph
Alphabet No. 5, which is the international version of ASCII; so there
is a worldwide standard based on ASCII.

John Savard

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: bit.listserv.ibm-main, alt.folklore.computers
Message-ID: <uisn9q8ec.fsf@earthlink.net>
References: <004f01c387d7$f60e0c20$e535a5d1@FJPx>
    <OF5917C77B.AA68DA44-ON88256DB2.0022B0E3-88256DB2.002620C5@enet.com>
Organization: Wheeler&Wheeler
Date: Wed, 01 Oct 2003 15:34:25 GMT
From: Anne & Lynn Wheeler <lynn@garlic.com>
Subject: Re: model 91/CRJE and IKJLEW


PaulW@ENET.COM (Paul Wendt) writes:
>
> Ah, CRJE...there's a text editor out of the past!

sometime late '68 (undergraduate at university), i had hacked HASP
... removed the 2780 support and misc. other stuff (to pick up size in
the program) and substituted 2741 and TTY support along with an editor
that implemented the CMS editor syntax for an early kind of CRJE (it
wasn't the actual CMS editor since it was quite non-reentrant, but the
same syntax rewritten from scratch).

I had previously added TTY support to CP/67 ... and had tried to
implement dynamic terminal recognition (between TTY and 2741).  After
it seemed to be working, the IBM CE got around to telling me that they
had taken short-cut on the 2702 and hardwired the oscilator to
individual ports. While it was possible to use the 2702 SAD command to
dynamically change the association of the line scanner type to each
individual line ... it wasn't actually possible to change the baud
rate on a line (since it was hard wired).

This in turn kicked off the university effort where four of
us got blamed for originating the PCM controller business:

http://www.garlic.com/~lynn/subtopic.html#360pcm

starting with an Interdata/3, reverse engineering the 360 channel
interface, building our own channel interface for the Interdata/3 and
writing 2702 emulator for the Interdata/3. All in order to get dynamic
terminal type (and baud rate) identification.

-- 
Anne & Lynn Wheeler | http://www.garlic.com/~lynn/ 
Internet trivia 20th anv http://www.garlic.com/~lynn/rfcietff.htm

 //////////////////////////////////////////////////////////////////////////////

Newsgroups: comp.terminals
NNTP-Posting-Host: panix5.panix.com
NNTP-Posting-Date: Wed, 1 Oct 2003 02:34:41 +0000 (UTC)
References: <oprv8x7b0f1w2lvw@news.online.no>
    <oheeb.194$815.7982@nnrp1.ozemail.com.au>
Message-ID: <bldeg8$6mj$1@panix5.panix.com>
Organization: Jeff's House of Electronic Parts
Date: 30 Sep 2003 22:34:48 -0400
From: Jeff Jonas <jeffj@panix.com>
Subject: Re: 20mA Current loop TTYs

>> I am the proud restorer of a PDP-7 computer, which utilized a 
>> 20mA current loop KSR33 [as its console].
>>
>> The KSR33 is dead. I'm working on fixing it, but I'd much much rather
>> be working on the logic circuits inside this DECbeauty.

There are RS232 <-> current loop adapters.
Build your own or buy pre-built:

    http://www.pccompci.com/converter/converter5.html
    http://www.lanode.com/tier2/cloop.htm
    http://www.decisioncards.com/adapt/current_loop.html

 //////////////////////////////////////////////////////////////////////////////

