The Teletype Story{1920s, 1930s, 1940s, british, communications, germany, italy, us, wwii}

Teletype, together with radio and air mail, are the most important means of communication introduced before the advent of Diesel Era but developed and perfected in the Interbellum. It doesn't enjoy iconic status like pneumatic mail. But it has a tremendous effect of presence. Anyone who begins a research of Dieselpunk roots will hear the teletype rattle sooner or later. A Teletype (also called teleprinter, teletypewriter, or TTY for TeleTYpe/TeleTYpewriter) is an electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communications channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the transmission medium. They could also serve as a command line user interface to early mainframes and minicomputers, sending typed data to the computer with or without printed output, and printing the response from the computer. The teleprinter evolved through a series of inventions by a number of engineers, including Royal Earl House, David E. Hughes, Edward Kleinschmidt, Charles Krum, Emile Baudot and Frederick G. Creed. A predecessor to the teleprinter, the stock ticker machine, was used as early as the 1870s as a method of displaying text transmitted over wires. A specially-designed telegraph typewriter was used to send stock exchange information over telegraph wires to the ticker machines. There were at least five major types of teleprinter networks. Most teleprinters used the 5-bit Baudot code (also known as ITA2). This limited the character set to 32 codes (25 = 32). One had to use a "FIGS" shift key to type numbers and special characters. Special versions of teleprinters had FIGS characters for specific applications, such as weather symbols for weather reports. Print quality was poor by modern standards. The Baudot code was used asynchronously with start and stop bits: the asynchronous code design was intimately linked with the start-stop electro-mechanical design of teleprinters. (Early systems had used synchronous codes, but were hard to synchronize mechanically). Other codes, such as ASCII, Fieldata and Flexowriter, were introduced but never became as popular as Baudot. Mark and space are terms describing logic levels in teleprinter circuits. The native mode of communication for a teleprinter is a simple series DC circuit that is interrupted, much as a rotary dial interrupts a telephone signal. The marking condition is when the circuit is closed (current is flowing), the spacing condition is when the circuit is open (no current is flowing). The "idle" condition of the circuit is a continuous marking state, with the start of a character signalled by a "start bit", which is always a space. Following the start bit, the character is represented by a fixed number of bits, such as 5 bits in the Baudot code, each either a mark or a space to denote the specific character or machine function. After the character's bits, the sending machine sends one or more stop bits. The stop bits are marking, so as to be distinct from the subsequent start bit. If the sender has nothing more to send, the line simply remains in the marking state (as if a continuing series of stop bits) until a later space denotes the start of the next character. The time between characters need not be an integral multiple of a bit time, but it must be at least the minimum number of stop bits required by the receiving machine. When the line is broken, the continuous spacing (open circuit, no current flowing) causes a receiving teleprinter to cycle continuously, even in the absence of stop bits. It prints nothing because the characters received are all zeros, the Baudot blank (or ASCII) null character. Earlier Teletype machines had three rows of keys and only supported upper case letters. They used the 5 bit Baudot code and generally worked at 60 words per minute. Teletypes with ASCII code were an innovation that came into widespread use in the same period as computers began to become widely available. Speed, intended to be roughly comparable to words per minute, was the standard designation introduced by Western Union for a mechanical teleprinter data transmission rate using the 5-bit baudot code that was popular in the 1940s and for several decades thereafter. Such a machine would send 1 start bit, 5 data bits, and 1.42 stop bits. This unusual stop bit time was actually a rest period to allow the mechanical printing mechanism to recycle. Since modern computer equipment cannot easily generate 1.42 bits for the stop period, common practice is to either approximate this with 1.5 bits, or to send 2.0 bits while accepting 1.0 bits receiving. For example, a "60 speed" machine is geared at 45.5 baud (22.0 ms per bit), a "66 speed" machine is geared at 50.0 baud (20.0 ms per bit), a "75 speed" machine is geared at 56.9 baud (17.5 ms per bit), a "100 speed" machine is geared at 74.2 baud (13.5 ms per bit), and a "133 speed" machine is geared at 100.0 baud (10.0 ms per bit). 60 speed became the de facto standard for amateur radio RTTY operation because of the widespread availability of equipment at that speed and the U.S. Federal Communications Commission (FCC) restrictions to only 60 speed from 1953 to 1972. Telex, news agency wires and similar services commonly used 66 speed services. There was some migration to 75 and 100 speed as more reliable devices were introduced. The teleprinter circuit was often linked to a 5-bit paper tape punch (or "reperforator") and reader, allowing messages received to be resent on another circuit. Complex military and commercial communications networks were built using this technology. Message centers had rows of teleprinters and large racks for paper tapes awaiting transmission. Skilled operators could read the priority code from the hole pattern and might 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. Many teleprinters had built-in paper tape readers and punches, allowing messages to be saved in machine-readable form and edited off-line. Morkrum made their first commercial installation of a printing telegraph with the Postal Telegraph Company in Boston and New York in 1910. It became popular with railroads, and the Associated Press adopted it in 1914 for their wire service.
In 1931 Edward Kleinschmidt formed Kleinschmidt Labs to pursue a different type design of Teletype. In 1944 Kleinschmidt demonstrated their lightweight unit to the Signal Corps and in 1949 their design was adopted for the Army's portable needs.
Teletype and Kleinschmidt competed for many decades following, each concentrating on their strengths.
"Teletype" machines tended to be large, heavy, and extremely robust, capable of running non-stop for months at a time if properly lubricated. In particular the Model 15 and Model 28 lines had very strong frames (cast iron[citation needed] in the Model 15; resilient sheet metal "plates" in the Model 28), heavy-duty mechanisms, and heavy sound-proofed cases. The "Kleinschmidt" line tended to be somewhat more typewriter-like—lighter, quieter, more aluminum and less iron. While Teletype Corp. developed a strong civilian customer base in addition to their military products, Kleinschmidt tended to be satisfied with the United States Signal Corps as their primary customer. Morkrum merged with their competitor E.E. Kleinschmidt to become Morkrum-Kleinschmidt Corporation shortly before being renamed the Teletype Corporation.
Creed & Company, a British manufacturer, built teleprinters for the GPO's teleprinter service. Their Teleprinter No. 7 (or Model 7) was probably the most distinguished of all: during WWII, dozens if not hundreds Creed 7s were installed at Bletchley Park, becoming a part of a system that "hacked" the German s' Enigma ciphers.
In Germany, Siemens & Halske company, (est. 1847), supplied teleprinters to Post Office, news agencies and of course to the military. Here's a German Fernschreibmaschine:
At the suggestion of Siemens, in 1933 the Deutsche Reichspost started operating the world's first public telex dialing network on a trial basis, with exchanges in Berlin and Hamburg.
Italian office equipment maker Olivetti (est. 1908) started to manufacture teleprinters in order to provide Italian post offices with modern equipment to send and receive telegrams. The first models typed on a paper ribbon, which was then cut and glued into telegram forms.
Olivetti T1 (1938 - 1948):
Although printing news, messages, and other text at a distance is still universal, the dedicated teleprinter tied to a pair of leased copper wires was made functionally obsolete by the fax, personal computer, inkjet printer, broadband, and the Internet. In the 1980s, packet radio became the most common form of digital communications used in amateur radio. Soon, advanced multimode electronic interfaces such as the AEA PK-232 were developed, which could send and receive not only packet, but various other modulation types including Baudot. This made it possible for a home or laptop computer to replace teleprinters, saving money, complexity, space and the massive amount of paper which mechanical machines used. As a result, by the mid-1990s, amateur use of actual Teletype machines had waned, though a core of "purists" still operate on equipment originally manufactured in the 1940s, 1950s, 1960s and 1970s, a tribute to the workmanship and durability of this equipment.
And for a dessert - teletype noir (Arthur Fellig aka Weegee got the news on Manhattan Police HQ teletype):



Comment by Pilsner Panther on December 14, 2010 at 12:35pm
Great article, but it should be added that the teletype machine was also adapted as the first really user-friendly human interface with early mainframe computers. Before that, the big boxes had to be programmed by flipping toggle switches on the front of the cabinet, a tedious process. The pioneering remote computer service providers like Tymshare would rent their customers a teletype, along with a modem that connected them to the computer center, a large building filled with mainframes such as the DEC PDP-10 (in the mid-to-late 1970's). Thanks to the development of time-sharing on mainframes, each user could have what appeared at the terminal end to be a "dedicated" computer, although it wasn't. So, they could "talk" to the system and it would "talk" back, but there were no monitor screens at the time... just those endless rolls of paper, and the motor hum and mechanical clickety-clack of the teletypes.