How Teleprinters Work and Their Applications

Teleprinters are amazing machines that revolutionized communication in the early 20th century. They use a combination of mechanical and electrical components to print out messages in real-time.

The first teleprinters were developed in the 1920s and were used primarily for transmitting stock prices and news over telegraph lines. These early machines were quite simple, consisting of a keyboard, a printer, and a transmission unit.

Teleprinters work by using a keyboard to input messages, which are then transmitted over a telegraph line to a receiving machine. The receiving machine prints out the message in real-time, allowing for instant communication over long distances.

The first commercial teleprinters were introduced in the 1930s and quickly gained popularity among businesses and governments. They were used for a wide range of applications, including news transmission, stock market updates, and even military communication.

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The Teletype Model 33 was first used commercially in 1963 as a seven-bit teleprinter code for American Telephone and Telegraph's Teletypewriter Exchange Service (TWX) using Teletype Model 33 teleprinters.

This early use of the Teletype Model 33 was influential in the development and interpretation of ASCII code characters, with the machine assignments for codes 17 (Control-Q, DC1, also known as XON) and 19 (Control-S, DC3, also known as XOFF) becoming de facto standards.

The Teletype Model 33 was also slow, which influenced the user interface of minicomputer operating systems, including UNIX. This slow speed was actually a result of the machine's design, which was meant for low-speed operation.

In 1965, Stanford University psychology professors Patrick Suppes and Richard C. Atkinson experimented with using computers to provide arithmetic and spelling drills via Teletypes and acoustic couplers to elementary school students.

The first computing experience of Bill Gates was on a Teletype Model 33, which is a testament to the machine's impact on the early computer industry.

Ray Tomlinson chose the "@" symbol on his Teletype Model 33 ASR keyboard for use in network email addresses in 1971.

The serial ports in Unix-like systems are named /dev/tty..., which is short for "Teletype".

Here is a list of some of the key features and influences of the Teletype Model 33:

Teleprinters used the 5-bit Baudot code, which limited the character set to 32 codes. This meant that special characters and numbers required a "FIGS" shift key to type.

The Baudot code was used asynchronously with start and stop bits, which was linked to the start-stop electro-mechanical design of teleprinters. Early systems had used synchronous codes, but were hard to synchronize mechanically.

The native mode of communication for a teletype is a simple series DC circuit that is interrupted, like a rotary dial. The marking condition is when the circuit is closed, and the spacing condition is when the circuit is open.

The start of a character is signaled by a space, and the stop bits are marking.

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Teleprinters used the 5-bit Baudot code, which limited the character set to 32 codes. This required the use of a "FIGS" shift key to type numbers and special characters.

The Baudot code was used asynchronously with start and stop bits, which was linked to the start-stop electro-mechanical design of teleprinters. Early systems used synchronous codes, but they were hard to synchronize mechanically.

A teletype circuit is a simple series DC circuit that is interrupted, similar to a rotary dial on a telephone. The marking condition is when the circuit is closed, and the spacing condition is when the circuit is open.

The start of a character is signaled by a space, and the stop bits are marking. When the line is broken, a teletype cycles continuously but prints nothing because it is receiving all zeros, the ASCII (or Baudot) NUL character.

Skilled operators could read the priority from the hole pattern on the paper tape and even feed a "FLASH PRIORITY" tape into a reader while it was still coming out of the punch. Routine traffic often had to wait hours for relay.

Some teleprinters had a built-in paper tape reader and punch, allowing messages to be created and edited off-line. This feature was useful for complex military and commercial communications networks.

A current loop was used to connect more than two teleprinters to the same wire circuit. This was a common setup in complex communication networks.

The Teletype Model 33 contains an answer-back mechanism that sends a unique identifying code to the sender when the recipient machine receives an enquiry character or WRU ("who are you") code. This verifies connection to the correct recipient.

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The receiving machine can also be set up to operate unattended, which was useful for sending messages across multiple time zones to locations where the office was closed overnight. This also took advantage of lower telecommunication charges for non-urgent messages.

The sole electric motor in the machine has to be left running continuously whenever unattended operation is expected. The motor displays a "HOT" warning label, clearly visible once the cover is removed.

The Space Shuttle's First Printer was a US military teleprinter, the AN/UG-74C, that was repurposed for the job.

It was based on a Motorola MC6800 and had a keyboard, a current loop digital interface, and even a rudimentary word processor, but all that was stripped out for the Shuttle.

The printer had a spinning 80-character-wide print drum and an array of 80 solenoid-powered hammers that banged out complete lines of text at a time.

A 600-baud frequency-shift keying (FSK) interface was added to patch into the spaceplane's comms system, making it Shuttle-worthy.

This printer was an interim solution until a fancier fax machine was ready, but it got the job done.

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Teleprinters were widely used in computing from the early days, and their legacy can still be seen today. They were used for input and output, and were especially popular as interactive time-sharing terminals.

The most common teletype machines had a 4-row keyboard and supported upper and lower case letters, which was an innovation at the time. The popular Teletype Model 33 used 7-bit ASCII code with an eighth parity bit.

Teleprinters were often used with paper tape to prepare input for the computer session offline, or to capture computer output. This was especially common with the popular ASR33 teletype.

Some of the common features of teleprinters include:

The printing mechanism of teleprinters is quite fascinating. It's usually geared to run at a maximum ten characters per second speed, or 100 words per minute (wpm).

There are many typefont options available, with 69 different factory-installed options listed in the Teletype Parts Bulletin for the Model 33. The type element, also known as a "typewheel", is cylindrical and capable of printing 64 characters.

The Model 33 prints on 8.5-inch wide paper, supplied on continuous 5-inch diameter rolls approximately 100 feet long. It prints at a fixed pitch of 10 characters per inch.

Here are the available printing speeds for the Model 33:

The Model 33 can operate either in half-duplex mode or in full-duplex mode.

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Teleprinters were used in various ways to facilitate communication and data processing. They were a crucial tool in the early days of computing.

In real-time circuit systems, teleprinters created a direct connection between two machines, allowing text to be transmitted instantly. This was used by systems like Telex and TWX. The US and UK systems even had telephone dials, while German systems used keyboard dialing.

Teleprinters were also used in leased line and radioteletype networks for data processing applications, such as integrating accounting, billing, and management departments within an organization. This was particularly useful for government and industry.

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Message switching systems, an early form of email, used electromechanical equipment to transmit messages. Military organizations had similar systems, like Autodin. These systems allowed users to send and receive messages in real-time.

Some teleprinter systems were used in broadcast mode, receiving information on "wire machines". This was used by news organizations like Associated Press and Reuters. The information was printed on receive-only teleprinters without keyboards or dials.

Teleprinters were also used in "loop" systems, where anything typed on one machine printed on all machines connected to the loop. This was used by American police departments to interconnect precincts.

In computing, teleprinters were used as input and output devices for some of the earliest computers, like the LGP-30. They were also the first interactive computer terminals, with no video display. Users typed commands after a prompt character appeared, which is where the command line interface originated.

The paper tape function on teleprinters was sometimes used to prepare input for computer sessions offline or to capture computer output. The ASR33 teletype used 7-bit ASCII code with an eighth parity bit instead of Baudot.

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Computers used teleprinters for input and output from the early days of computing. Punched card readers and fast printers replaced teleprinters for most purposes, but teleprinters continued to be used as interactive time-sharing terminals until video displays became widely available in the late 1970s.

The popular Teletype Model 33 used 7-bit ASCII code (with an eighth parity bit) instead of Baudot. This was a significant innovation that allowed for upper and lower case letters.

Teleprinters were often used to prepare input for the computer session offline, or to capture computer output. Paper tape was sometimes used for this purpose.

The common modem communications settings, Start/Stop Bits and Parity, stem from the Teletype era. This is why you'll often see these settings referenced in computing contexts.

In early operating systems, serial communication lines were often connected to teleprinters and were given device names starting with tt. This convention was adopted by many other operating systems.

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Some of the earliest computers used teleprinters for input and output, and they had no video display. Users typed commands after a prompt character appeared, which is where the command line interface originated.

Here's a list of some common Teletype models and their features:

In computing, especially under Unix and Unix-like operating systems, teletypewriter has become the name for any external console device, like a user dialing in to the system, or a modem on a serial port. Such devices have the prefix tty, such as /dev/tty13.

The Teletypesetter was a game-changer for the newspaper industry, allowing for higher production rates and the ability to distribute identical content across wide geographical areas.

It used a six-bit code called the Teletypesetter code (TTS), which was first demonstrated in 1928 and gained widespread use in the 1950s.

This code could represent a full set of upper and lower case characters, digits, symbols commonly used in newspapers, and typesetting instructions.

The TTS code included "shift in" and "shift out" codes, allowing it to switch between different font styles, such as italics or bold type.

The Teletypesetter produced aligned text, taking into consideration character widths and column width, or line length.

A Model 20 Teletype machine with a paper tape punch ("reperforator") was installed at subscriber newspaper sites, which would punch paper tapes that could be read by a tape reader.

This tape reader was attached to a "Teletypesetter operating unit" installed on a Linotype machine, which would actuate a mechanical box to operate the Linotype's keyboard and other controls.

This allowed for higher production rates for the Linotype, and was used both locally and remotely, using tape transmitters and receivers.

Remote use played an essential role for distributing identical content, such as syndicated columns, news agency news, classified advertising, and more, to different publications across wide geographical areas.

In later years, the incoming 6-bit current loop signal carrying the TTS code was connected to a minicomputer or mainframe for storage, editing, and eventual feed to a phototypesetting machine.

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The Teletype Model 33 was the first commercially used teleprinter in 1963, as part of American Telephone and Telegraph's Teletypewriter Exchange Service (TWX).

This early model had a significant influence on the development of ASCII code characters. Its machine assignments for codes 17 (Control-Q, DC1) and 19 (Control-S, DC3) became de facto standards.

The slow speed of the Teletype Model 33 influenced the user interface of minicomputer operating systems, including UNIX, which was designed to be written and edited on such a device.

Bill Gates' first computing experience was with a Teletype Model 33.

In 1965, Stanford University professors Patrick Suppes and Richard C. Atkinson experimented with using computers to provide arithmetic and spelling drills to elementary school students via Teletypes and acoustic couplers.

Ray Tomlinson chose the "@" symbol on his Teletype Model 33 ASR keyboard for use in network email addresses in 1971.

The serial ports in Unix-like systems are named /dev/tty..., which is short for "Teletype".

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The dedicated teleprinter was made functionally obsolete by the fax, personal computer, inkjet printer, email, and the Internet.

In the 1980s, packet radio became the most common form of digital communications used in amateur radio.

Teleprinters were gradually replaced in new installations by much faster dot-matrix printers and video terminals in the middle-to-late 1970s.

The introduction of integrated circuits and semiconductor memory allowed the price of cathode-ray tube-based terminals to rapidly fall below the price of a Teletype teleprinter.

Teletype Corporation shut down Model 33 production in 1981 due to falling sales.

A malfunctioning Teletype served as a plot point in the 1971 science fiction film The Andromeda Strain.

Some Teletype machines remained in working use, such as a scientific project in Australia, which used one connected to a phase ionosonde until 1984.

The price of early video terminals, such as the Tektronix 4010, was around $10,000 in 1970, equivalent to $103,000 today.

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The Teletype Model 33 was designed to fit into a small office space and operate up to two hours per day on average. It's a remarkable machine that can fit into a small office space.

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The machine is powered by a single electric motor located at the rear, which runs continuously as long as power is on. This motor generates a familiar humming and slight rattle from its vibration. The noise level increases considerably whenever the printing or paper tape mechanisms are operating.

The machine stands 34 inches high, 22 inches wide, and 18.5 inches deep, weighing 75 pounds on the stand, including paper. It requires less than 4 amperes at 115 VAC and 60 Hz.

The recommended operating environment for the Teletype Model 33 is a temperature of 40 to 110 °F (4 to 43 °C), a relative humidity of between 2 and 95 percent, and an altitude of 0 to 10,000 feet (0 to 3,048 m).

The entire Model 33 ASR mechanism requires periodic application of grease and oil in approximately 500 locations. This includes the tape punch, which required oiled paper tape to keep its mechanism lubricated.

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The Teletype Model 33 is a machine designed to fit into a small office space, matching with other office equipment of the time and operating up to two hours per day on average.

It's made of die-cast metal, but some parts are made of materials that aren't as durable, such as self-tapping screws and parts that snap together without bolting.

The machine is powered by a single electric motor located at the rear, which runs continuously as long as power is on, generating a humming and slight rattle from its vibration.

The noise level increases when the printing or paper tape mechanisms are operating, making it a familiar sound for those who work with newswires or computer terminals.

A mechanical bell is activated by code 07 (Control-G, also known as BEL) to draw special attention when needed.

The machine stands 34 inches high, 22 inches wide, and 18.5 inches deep, weighing 75 pounds on the stand, including paper.

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Here are the dimensions and weight of the machine:

The machine requires less than 4 amperes at 115 VAC and 60 Hz, and can operate in a temperature range of 40 to 110 °F (4 to 43 °C), with a relative humidity of between 2 and 95 percent, and an altitude of 0 to 10,000 feet (0 to 3,048 m).

The patents behind the development of the Teletype machine are quite fascinating. US Patent 1665594, "Telegraph printer (Type 12 Teletype)", was issued on April 1, 1928.

The first patent for a Teletype machine was for a telegraph printer, which was a crucial component in the early days of telecommunications. This printer was designed to print messages received through the telegraph system.

US Patent 1745633, "Telegraph receiver (Type 14 Teletype)", was issued on February 1, 1930, and marked a significant improvement in the technology. This patent introduced a new type of telegraph receiver that was more efficient and reliable.

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The development of the Teletype machine continued to evolve over the years, with new patents being issued. One notable example is US Patent 1904164, "Signalling system and apparatus therefor (Type 15 Teletype)", issued on April 1, 1933.

Here are some key patents related to the Teletype machine:

The Frequency-Shift Teletypewriter, patented in 1970, was a significant innovation in the field of telecommunications.

Restoring a teleprinter to its former glory requires some TLC. A teleprinter, at its heart, is an automatic typewriter with electric controls and smarts to decode incoming messages.

Cleaning an old teleprinter is a must before restoration. It's common for older mechanical devices to accumulate grime, so a good degreasing solvent bath is in order. The keyboard is usually the dirtiest part, so it gets an overnight soak.

Lubrication is key to getting a teleprinter up and running again. The manufacturer's manuals are a valuable resource, and synthetic motor oil is the way to go. With hundreds of parts to oil, it's a painstaking process, but necessary for a smooth operation.

A teleprinter's wiring can be a challenge to work with, especially when dealing with asbestos insulation. In this case, the original wiring was left intact, and a new power supply was used to get the machine up and running.

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Kleinschmidt Labs was formed by American inventor Edward Kleinschmidt in 1931 to pursue a different design of teleprinter.

In 1944, Kleinschmidt demonstrated their lightweight teleprinter unit to the Signal Corps, marking a significant milestone in the company's history.

Their design was adopted for the Army's portable needs in 1949, a testament to the company's innovative approach to teleprinters.

By 1956, Kleinschmidt Labs had merged with Smith-Corona, which then merged with the Marchant Calculating Machine Co., forming the SCM Corporation.

Kleinschmidt machines used standard military designations, such as the TT-4/FG teleprinter, which was likely used by the military for its portability and reliability.

The TT-117/FG teleprinter and TT-179/FG tape reperforator were also part of the Kleinschmidt product line, designed to meet the Army's communication needs.

By 1979, the Kleinschmidt division was shifting its focus to Electronic Data Interchange, a significant departure from its mechanical product roots.

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I've always been fascinated by the revival of old technologies, and the teletype machine is a great example of this phenomenon. The teletype machine, also known as a teleprinter, is essentially an automatic typewriter that's electrically controlled and can decode incoming messages.

The process of resurrecting an old teletype machine like the 1930s design refurbished by AethericLtd involves a thorough cleaning, lubrication, and rewiring. The machine was first given a bath to remove dirt and grime that had accumulated over the years, with the keyboard being the dirtiest part requiring an overnight soak.

AethericLtd consulted the machine's manuals, which were available online, to determine the best course of action for lubrication. They used synthetic motor oil to lubricate the hundreds of parts, ensuring that everything was properly oiled before starting the rewiring process.

The original wiring in the machine used Deltabeston wire, a type of wire with asbestos insulation that was common in the early 20th century. To play it safe, the original wiring was left intact, and a new power supply was installed to provide the necessary voltage to run the machine. The power supply used a 120 VDC, 200 mA supply through a 2 KΩ, 10 W resistor.

Here's a list of some of the key features of teletype machines:

These features were often indicated by a model number, with the 33-ASR being a particularly popular model that was widely used in the early minicomputer era.