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Teletypewriter machines
- under construction
This part of the Crypto Museum website deals with automatic
(analogue or digital)
telegraphy by means of typewriter-style devices, using a binary code
such as the common 5-bit Baudot code,
or the 7/8-bit ASCII standard.
Such systems are generally known as
Teletype machines (after the Teletype brand),
Teleprinters,
Telex (short for Teleprinter Exchange),
Tele-Typewriter
or by its abbreviation TTY.
On these pages we will use the generic name Telex to identify these systems.
Telex machines are operated over land lines (TTY)
or via radio (RTTY), mainly using the standard speed of 45.45 baud (USA)
or 50 baud (Europe). The use over radio links is also known as
Telex Over Radio (TOR).
Punched paper tape was commonly used with telex
equipment for storing and (re)transmitting messages.
Although telex has been superceeded by modern computers, some computer
terminal sessions are still called TTY, for example on UNIX-like
operating systems.
Although Telex machines are not cryptographic devices,
many of them were used in combination with external
cipher machines and some even had built-in cryptographic capabilities. For that reason, some telex machines are described on this
website. For a more exhaustive overview of telex machines,
please check out the Telex Museum of Henning Treumann in Germany [1].
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Telex equipment on this website
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Telex manufacturers on this website
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For many years, Telex was the de-facto standard for communication
with the Armies world-wide.
It was introduced long before WWII (in 1849) and lasted until the 1990s.
It was also used by press agencies, governments, large corporations and
by the police. Telex can be employed reliably over (fixed) land lines
as well as over radio (HF). In the past, most countries had their own
Telex network, consisting of decicated land lines and special exchanges,
but towards the 2000s most of them were gradually phased out.
Today, Telex is still used by radio amateurs (HAMs).
Although most telex systems use the 5-bit digital
ITA2 code, generally
known the Baudot code,
there are systems that use a less-common standards,
such as the multi-tone COQUELET code,
often used in France,
and the 14-bit ETK standard
that was introduced by Gretag
in the 1950s.
Such systems were considered more fault-tolerant but never met
wide-spread acceptance.
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Telex — short for Teleprinter Exchange
— is a world-wide communications system
of the past. It was once one of the most important methods of communication
between companies, embassies, governmental bodies, public services, etc.,
but lost its popularity in the 1980s, when they were gradually replaced by
fax machines (which have now been superseded by modern computers).
Nevertheless, they are marvels of electrical and mechanical engineering,
and many collectors and museums make an effort to preserve them for the future
and keep them running if possible. This can be done via wire (TTY) or via
radio (RTTY). There are several initiatives that allow (private) collectors
and museums to take part in a modern world-wide network of teleprinters,
such as TelePhone
and i-Telex listed below, with the latter being the
most future-proof system.
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In order to keep old Teleprinters running and to be able to demonstrate
the surviving machines, a group of enthusiasts has setup the so-called
TelexPhone project [2].
It allows telex machines to be connected to a hobbyist telex network
using standard (analogue) telephone lines (POTS).
A customized modem (TxP) has been developed to convert the special Telex
signals into standard modem data, allowing any standard telex machine to
be connected to another telex anywhere in the world, without any
modifications to the equipment at either side. This project has meanwhile
evolved into TelexPhone 2, also known as i-Telex, for connection
via the internet (see below).
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As analogue telephone lines are gradually disappearing, and telecom
providers are discouraging the use of such lines, the above TelexPhone idea
has been ported to the internet. By using a simple interface, it is now
possible to run teleprinters on a world-wide virtual telex network [6].
➤ More about i-Telex (off-site)
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Telex machines were developed and produced world-wide by a variety
of manufacturers. Most of these machines were compatible in one way
or another. The initial machines worked at the rather low baud-rate
of 45.45 baud or 50 baud, but later machines were capable of running
at 75, 100 and even speeds up to 150 baud as well. The following manufacturers produced
telex equipment:
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- ACEC
- Creed
- Gretag
- Hasler
- Lorenz (SEL)
- Olivetti
- OKI
- Philips
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Alternative devices, which resemble a teleprinter but do not follow
the Baudot/ITA-2 standard, were developed by:
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- Teletypewriter
- Teleprinter
- Teletype
- TTY (TeleType)
- RTTY (Radio TeleType)
- Telex (Teleprinter Exchange)
- Fernschreiber (German)
- Verreschrijver (Dutch)
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When bringing old teleprinter equipment back to life, it may be useful
to know how existing telephone connectors were wired at the time for use
in combination with telex equipment. Note that the wiring of a telex machine
can be very different from a standard telephone set and that many different
configurations are possible. Also note that a current-loop system is used.
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One some older teleprinters, in particular in the Netherlands, a large
6-pin circular connector was often used. These connectors were also used on
early cipher machines like the
Philips Ecolex II
and Ecolex IV.
In later years, the 6-pin connectors and sockets were often replaced
by the circular Walzenstecker (ADoS)
or the more popular ADo 8 (see below).
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- TX relay A (common)
- TX relay Z (mark)
- TX relay T (space)
- 120Ω RX relay (with 6)
- Alarm contact (with 5)
- Alarm contact (with 4)
- 120Ω RX relay (with 3)
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The eldest connector used for teleprinters in Europe is the so-called
Walzenstecker (wheel plug); a circular plug with four contacts
that was originally used for the connection of telephone equipment,
wired as (1) a, (2) b, (3) bell and (4) gound, but reused to accomodate
the TX and RX contacts of a teleprinter. The pin-out for use incombination
with telex equipment is given below.
The official designator for this plug is Anschlußdosenstöpsel ZB 27,
or ADoS ZB 27.
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The Walzenstecker shown above was later succeeded by the more
versatile 8-pin connector known as ADo 8. This connector was used for
a variety of equipment and had two 'coded' guide pins at the centre,
to ensure that the plug is entered into the socket with the right side
up, and to avoid the wrong plug being inserted into the wrong socket.
The sockets are 'programmable'.
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- TX a (a1)
- TX b (b1)
- RX a (a2)
- RX b (b2)
- Bridge to 6 1
- Bridge to 5 1
- -
- -
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The orientation of two small discs inside the socket can be altered in
order to configure it for various applications.
The image above shows the correct configuration for use with
a teleprinter. Pins 1-4 are used for the same signals as on the earlier
Walzenstecker. The bridge between pins 5 and 6 is optional 1 and is
used on newer equipment to signal that the teleprinter is connected.
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This is a bridge inside the socket (not the plug).
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Adapter between ADo 8 and Walzenstecker
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The table below shows the wiring for an adapter from ADo-8 to Walzenstecker
or vice versa.
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Signal
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ADo 8 1
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Walze 2
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Colour
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Description
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a1
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1
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1 (a)
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white
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TX a
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b1
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2
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2 (b)
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brown
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TX b (no bridge to 3)
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a2
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3
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3 (w2)
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yellow
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RX a (no bridge to 2)
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b2
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4
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4 (c)
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green
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RX b
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Bridge between 5 and 6 in ADo-8 socket only.
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Original name when used for telephone shown in brackets.
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RTTY
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Radio Teletype
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TOR
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Telex Over Radio
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TTY
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Teletype
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Baud
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Bits per second
Common expression for specifying the transmission speed of a digital
telegraphic data signal, derived from the
Baudot encoding standard,
also known as bits-per-second (bps).
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© Crypto Museum. Created: Saturday 07 April 2012. Last changed: Monday, 09 January 2023 - 15:23 CET.
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