Teleprinter

A teleprinter—also known as a teletypewriter, teletype, or TTY—is an electromechanical device designed to send and receive typed messages over various types of communication channels. Used in both point-to-point and point-to-multipoint configurations, teleprinters played a central role in telegraphy, early data communications, and later in computer interaction. From the late nineteenth century onward, they automated message transmission and enabled high-speed communication without the need for skilled Morse code operators. Though largely replaced today by digital terminals and computer networks, teleprinters retain specialised uses in aviation and accessible telecommunications.
Teleprinters could interface with telegraph lines, create and read punched tape for data storage, or connect to computers and timesharing systems via modems. Their evolution marks a significant chapter in the development of communication technology.

Early Development and Background

Teleprinter technology emerged through a succession of nineteenth-century innovations in telegraphy. Early electrical telegraph systems of the 1830s and 1840s relied on Morse keys and operators trained to send and interpret Morse code. Teleprinters replaced this manual process with automated printing mechanisms and keyboard inputs, making communication faster and less labour-intensive.
Key contributors to the development of teleprinter-related technologies included Samuel Morse, Alexander Bain, Royal Earl House, David Edward Hughes, Émile Baudot, Donald Murray, Charles L. Krum, Edward Kleinschmidt, and Frederick G. Creed. Their combined innovations laid the foundation for synchronous communication, coded transmission, and automated message output.

Nineteenth-Century Foundations

In 1835 Samuel Morse devised a recording telegraph, establishing Morse code as a global communication system. Shortly afterwards, Cooke and Wheatstone received British patents for telegraphy, including designs for type-printing telegraphs. Alexander Bain’s 1841 electromagnetic printing telegraph attempted to synchronise a typewheel and rotating paper drum using clockwork and centrifugal governors. Although complex, these ideas paved the way for later synchronous systems.
Royal Earl House advanced this technology with his 1846 printing telegraph, which linked piano-like keyboards to synchronised typewheels at distant stations. The system transmitted around forty readable words per minute and represented an early form of synchronous data transmission. By 1849, a landline teleprinter connection between Philadelphia and New York signalled the promise of automated long-distance text communication.
David Edward Hughes’s 1855 design improved upon earlier machines and was adopted by the newly established Western Union Telegraph Company. By the late nineteenth century, teleprinters became more reliable as companies consolidated and infrastructure expanded.

Baudot Code and Keyboard Innovations

A major milestone came with Émile Baudot’s 1874 five-unit code, widely used in France from 1877 and adopted by the British Post Office in the 1890s. Baudot’s code allowed efficient transmission with minimal hardware and became internationally influential.
In 1901 Donald Murray developed a modified version of this code to suit a typewriter-like keyboard. Murray introduced punched-tape keyboard perforators and transmitters that allowed operators to prepare messages before transmission. His coding scheme reduced mechanical wear by assigning shorter code combinations to common letters and introduced control characters such as carriage return and line feed, which remain essential in computing.

Twentieth-Century Advances and Commercialisation

American engineers expanded teleprinter technology in the early twentieth century. Frank Pearne initiated research into practical printing telegraphs in 1902 with support from Joy Morton. Mechanical engineer Charles L. Krum filed a patent for a typebar page printer in 1903, followed by a typewheel printer patent in 1904. Howard Krum later contributed the crucial start–stop synchronisation method that enabled stable asynchronous transmission, making teleprinters far more practical.
By 1908 the Morkrum Company produced its first operational teleprinter, later used by the Alton Railroad. In 1910 it installed the first commercial teletypewriter system on Postal Telegraph Company lines between Boston and New York. Competing innovations followed, including Edward Kleinschmidt’s typebar page printer in 1916. In 1919 Kleinschmidt submitted a patent involving an improved start–stop method, though the fundamental concept predated both Morkrum and Kleinschmidt, having been proposed as early as 1870.
To avoid prolonged patent disputes, Morkrum and Kleinschmidt merged in 1924 as the Morkrum-Kleinschmidt Company. They integrated the strongest features of both designs, producing improved typewheel printers. Meanwhile, Frederick G. Creed’s British company entered the field the same year, contributing to rapidly expanding global teleprinter infrastructure.

Role in Computing and Telecommunications

As digital technologies emerged, teleprinters were adapted for early computing. In the 1950s they served as user terminals, sending typed commands to computers and printing responses. Many models included punched-tape readers and punches, enabling storage and transmission of data for computing applications.
With modems, teleprinters could communicate over standard telephone lines, a configuration widely used in timesharing environments. This arrangement allowed remote access to computers long before the advent of electronic displays. The abbreviation TTY became common in operating systems such as Unix to describe terminal interfaces, a linguistic legacy that persists despite the decline of electromechanical hardware.
Teleprinters later gave way to electronic terminals with monitors, which provided faster, quieter, and more flexible interaction. However, remnants of teleprinter terminology persisted in software, protocols, and interface naming.

Contemporary Uses

Although largely obsolete in mainstream telecommunications, teleprinters remain active in specific industries. Aviation relies on them through systems such as the Aeronautical Fixed Telecommunication Network and airline teletype services, which maintain high reliability and broad compatibility. Variants of teleprinters are also used as Telecommunications Devices for the Deaf (TDDs), enabling text communication over ordinary telephone lines for users with hearing impairments.
Teleprinters stand as key artefacts in the evolution of long-distance communication and computing. Their development bridged the gap between manual telegraphy and fully electronic digital communication, shaping modern data transmission and human–machine interaction.