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Telegraphy
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Telegraphy is the long-distance transmission of messages without physical transport of written messages. It is a compound term formed from the Greek words tele (τηλε) = far and graphein (γραφειν) = write. Radiotelegraphy or wireless telegraphy transmits messages using radio.
[edit] Terminology
A telegraph is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. The word telegraph alone now generally refers to an electrical telegraph. Wireless telegraphy is also known as "CW", for continuous wave (a carrier modulated by on-off keying), as opposed to the earlier radio technique of using a spark gap.[citation needed]
A telegraph message sent by an electrical telegraph operator or telegrapher using Morse code (or a printing telegraph operator using plain text) was known as a telegram. A cablegram (see cablegram) was a message sent by a submarine telegraph cable,[1] often shortened to a cable or a wire. Later, a Telex was a message sent by a Telex network, a switched network of teleprinters similar to a telephone network.
Before long distance telephone services were readily available or affordable, telegram services were very popular and the only way to convey information speedily over very long distances. Telegrams were often used to confirm business dealings and were commonly used to create binding legal documents for business dealings.[2]
A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. The teleostereograph machine, a forerunner to the modern electronic fax, was developed by AT&T's Bell Labs in the 1920s; however, the first commercial use of image facsimile telegraph devices date back to the 1800s. It was made by Samuel F. B. Morse (the coinventor of morse code).
A diplomatic telegram, also known as a diplomatic cable, is the term given to a confidential communication between a diplomatic mission and the foreign ministry of its parent country.[3][4] These continue to be called telegrams or cables regardless of the method used for transmission.
[edit] Optical telegraph
- Main articles: Semaphore line (visual telegraphy using signal arms or shutters), Flag semaphore (using hand-held flags), Signal lamp (visual naval communications) and Heliograph (visual communications using reflected sunlight)
The first telegraphs came in the form of optical telegraph including the use of smoke signals, beacons or reflected light, which have existed since ancient times. A semaphore network invented by Claude Chappe operated in France from 1792 through 1846.[5] It helped Napoleon enough to be widely imitated in Europe and the U.S. In the Peninsular War (1807-1814), several similars telegraphs had been used in the Lines of Torres Vedras, by the anglo-portuguese army. The Prussian system was put into effect in the 1830s. The last commercial semaphore link ceased operation in Sweden in 1880.
Semaphores were able to convey information more precisely than smoke signals and beacons, and consumed no fuel. Messages could be sent at much greater speed than post riders and could serve entire regions. However, like beacons, smoke and reflected light signals they were highly dependent on good weather and daylight to work (practical electrical lighting was not available until about 1880). They required operators and towers every 30 km (20 mi), and could only accommodate about two words per minute. This was useful to governments, but too expensive for most commercial uses other than commodity price information. Electric telegraphs were to reduce the cost of sending a message thirtyfold compared to semaphores, and could be utilized non-stop, 24 hours per day, independent of the weather or daylight.
Elevated locations where optical telegraphs were placed for maximum visibility were renamed to Telegraph Hill, such as Telegraph Hill, San Francisco, and Telegraph Hill in the PNC Bank Arts Center in New Jersey.
[edit] Electrical telegraphs
One very early experiment in electrical telegraphy was an electrochemical telegraph created by the German physician, anatomist and inventor Samuel Thomas von Sömmering in 1809, based on an earlier, less robust design of 1804 by Spanish-Catalan polymath and scientist Francisco Salvá i Campillo.[6] Both their designs employed multiple wires (up to 35) in order to visually represent most Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers (in von Sömmering's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid. As an electric current was applied by the sender representing each digit of a message, it would at the recipient's end electrolyse the acid in its corresponding tube, releasing a stream of hydrogen bubbles next to its associated letter or numeral. The telegraph receiver's operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate.[6]
One of the earliest electromagnetic telegraph designs was created by Pavel Schilling in 1832.[citation needed]
Carl Friedrich Gauss and Wilhelm Weber built and first used for regular communication the electromagnetic telegraph in 1833 in Göttingen, connecting Göttingen Observatory and the Institute of Physics, covering a distance of about 1 km.[7] The setup consisted of a coil which could be moved up and down over the end of two magnetic steel bars. The resulting induction current was transmitted through two wires to the receiver, consisting of a galvanometer. The direction of the current could be reversed by commuting the two wires in a special switch. Therefore, Gauss and Weber chose to encode the alphabet in a binary code, using positive current and negative as the two states.
A replica commissioned by Weber for the 1873 World Fair based on his original designs is on display in the collection of historical instruments in the Department of Physics at University of Göttingen.
There are two versions of the first message sent by Gauss and Weber: the more official one is based on a note in Gauss's own handwriting stating that "Wissen vor meinen – Sein vor scheinen" ("knowing before opining, being before seeming") was the first message sent over the electromagnetic telegraph.
The more anecdotal version told in Göttingen observatory is that the first message was sent to notify Weber that the observatory's servant was on the way to the institute of physics, and just read "Michelmann kommt" ("Michelmann is on his way"), possibly as a test who would arrive first.
The first commercial electrical telegraph was co-developed by Sir William Fothergill Cooke and Charles Wheatstone, and entered use on the Great Western Railway in Britain. It ran for 13 miles (21 km) from Paddington station to West Drayton and came into operation on 9 July 1839.[8] It was patented in the United Kingdom in 1837, and was first successfully demonstrated by Cooke and Wheatstone on 25 July 1837 between Euston and Camden Town in London.[9] In 1843 Scottish inventor Alexander Bain invented a device that could be considered the first facsimile machine. He called his invention a "recording telegraph". Bain's telegraph was able to transmit images by electrical wires. In 1855 an Italian abbot, Giovanni Caselli, also created an electric telegraph that could transmit images. Caselli called his invention "Pantelegraph". Pantelegraph was successfully tested and approved for a telegraph line between Paris and Lyon.
[edit] Morse telegraph
An electrical telegraph was independently developed and patented in the United States in 1837 by Samuel Morse. His assistant, Alfred Vail, developed the Morse code signaling alphabet with Morse. America's first telegram was sent by Morse on 6 January 1838, across two miles (3 km) of wire at Speedwell Ironworks near Morristown, New Jersey. The message read "A patient waiter is no loser."
On 24 May 1844, he sent the message "WHAT HATH GOD WROUGHT" from the Old Supreme Court Chamber in the Capitol in Washington to the old Mt. Clare Depot in Baltimore. This message (quoting Numbers 23:23) was chosen by Annie Ellsworth of Lafayette, Indiana,[10] the daughter of Patent Commissioner Henry Leavitt Ellsworth. The message was all capital letters because the original Morse code alphabet had no question mark or lower case.
The Morse/Vail telegraph was quickly deployed in the following two decades; the overland telegraph connected the west coast of the continent to the east coast by 24 October 1861, bringing an end to the Pony Express.
[edit] Oceanic telegraph cables
The first commercially successful transatlantic telegraph cable was successfully completed on 18 July 1866. The lasting connections were achieved by the ship SS Great Eastern, captained by Sir James Anderson.[11] Earlier transatlantic submarine cables installations were attempted in 1857, 1858 and 1865. The 1857 cable only operated intermittently for a few days or weeks before it failed. The study of underwater telegraph cables accelerated interest in mathematical analysis of very long transmission lines. The telegraph lines from Britain to India were connected in 1870 (those several companies combined to form the Eastern Telegraph Company in 1872).
Australia was first linked to the rest of the world in October 1872 by a submarine telegraph cable at Darwin.[12] This brought news reportage from the rest of the world.[13]
Further advancements in telegraph technology occurred in the early 1870s, when Thomas Edison devised a full duplex two-way telegraph and then doubled its capacity with the invention of quadruplex telegraphy in 1874.[14] Edison filed for a U.S. patent on the duplex telegraph on 1 September 1874 and received U.S. Patent 480,567 on 9 August 1892.
The telegraph across the Pacific was completed in 1902, finally encircling the world.
[edit] Wireless telegraphy
Nikola Tesla and other scientists and inventors showed the usefulness of wireless telegraphy, radiotelegraphy, or radio, beginning in the 1890s. Alexander Stepanovich Popov demonstrated to the public his wireless radio receiver, which was also used as a lightning detector, on May 7, 1895. He proudly demonstrated his wireless receiver before a group of reporters on a stormy August evening in 1895. It was attached to a long 30 foot pole that he held aloft to maximize the signal. When asked by one of the reporters if it was a good idea to hold this metal rod in the middle of a storm he replied that all was well. After being struck (and nearly killed) by a bolt of lightning he proudly announced to the world that his invention also served as a 'lightning detector'.
Albert Turpain sent and received his first radio signal, using Morse code, in France, up to 25 meters in 1895.[15]
Guglielmo Marconi sent and received his first radio signal in Italy up to 6 kilometres in 1896. On 13 May 1897, Marconi, assisted by George Kemp, a Cardiff Post Office engineer, transmitted the first wireless signals over water to Lavernock (near Penarth in Wales) from Flat Holm.[16] Having failed to interest the Italian government, the twenty-two year old inventor brought his telegraphy system to Britain and met William Preece, a Welshman, who was a major figure in the field and Chief Engineer of the General Post Office. A pair of masts about 34 metres (112 ft) high were erected, at Lavernock Point and on Flat Holm. The receiving mast at Lavernock Point was a 30-metre (98 ft) high pole topped with a cylindrical cap of zinc connected to a detector with insulated copper wire. At Flat Holm the sending equipment included a Ruhmkorff coil with an eight-cell battery. The first trial on 11 and 12 May failed but on the 13th the mast at Lavernock was extended to 50 metres (164 ft) and the signals, in Morse code, were received clearly. The message sent was "ARE YOU READY"; the Morse slip signed by Marconi and Kemp is now in the National Museum of Wales.
In 1898 Popov accomplished successful experiments of wireless communication between a naval base and a battleship.
In 1900 the crew of the Russian coast defense ship General-Admiral Graf Apraksin as well as stranded Finnish fishermen were saved in the Gulf of Finland because of exchange of distress telegrams between two radiostations, located at Hogland island and inside a Russian naval base in Kotka. Both stations of wireless telegraphy were built under Popov's instructions.
In 1901, Marconi radiotelegraphed the letter "S" across the Atlantic Ocean from his station in Poldhu, Cornwall to St. John's, Newfoundland.
Radiotelegraphy proved effective for rescue work in sea disasters by enabling effective communication between ships and from ship to shore.
[edit] Telegraphic improvements
A continuing goal in telegraphy has been to reduce the cost per message by reducing hand-work, or increasing the sending rate.[citation needed] There were many experiments with moving pointers, and various electrical encodings. However, most systems were too complicated and unreliable. A successful expedient to increase the sending rate was the development of telegraphese.
Other research[specify] focused on the multiplexing of telegraph connections. By passing several simultaneous connections through an existing copper wire, capacity could be upgraded without the laying of new cable, a process which remained very costly. Several technologies were developed like Frequency-division multiplexing. Long submarine communications cables became possible in segments with vacuum tube amplifiers between them.
With the invention of the teletypewriter, telegraphic encoding became fully automated. Early teletypewriters used the ITA-1 Baudot code, a five-bit code. This yielded only thirty-two codes, so it was over-defined into two "shifts," "letters" and "figures". An explicit, unshared shift code prefaced each set of letters and figures.
The airline industry remains one of the last users of teletype and in a few situations still sends messages over the SITA or AFTN networks. For example, The British Airways operations computer system (FICO) as of 2004[update] still used teletype to communicate with other airline computer systems.[citation needed] The same goes for Programmed Airline Reservation System (PARS) and IPARS that used a similar shifted six-bit Teletype code, because it requires only eight bits per character, saving bandwidth and money. A teletype message is often much smaller than the equivalent EDIFACT or XML message. In recent years as airlines have had access to improved bandwidth in remote locations, IATA standard XML is replacing Teletype as well as EDI.
The first electrical telegraph developed a standard signaling system for telecommunications. The "mark" state was defined as the powered state of the wire. In this way, it was immediately apparent when the line itself failed. The moving pointer telegraphs started the pointer's motion with a "start bit" that pulled the line to the unpowered "space" state. In early Telex machines, the start bit triggered a wheeled commutator run by a motor with a precise speed (later, digital electronics). The commutator distributed the bits from the line to a series of relays that would "capture" the bits. A "stop bit" was then sent at the powered "mark state" to assure that the commutator would have time to stop, and be ready for the next character. The stop bit triggered the printing mechanism. Stop bits initially lasted 1.42 baud times (later extended to two as signaling rates increased), in order to give the mechanism time to finish and stop vibrating. Hence an ITA-2 Murray code symbol took 1 start, 5 data, and 1.42 stop (total 7.42) baud times to transmit.[17]
[edit] Telex
By 1935, message routing was the last great barrier to full automation. Large telegraphy providers began to develop systems that used telephone-like rotary dialing to connect teletypes. These machines were called "Telex" (TELegraph EXchange). Telex machines first performed rotary-telephone-style pulse dialing for circuit switching, and then sent data by Baudot code. This "type A" Telex routing functionally automated message routing.
The first wide-coverage Telex network was implemented in Germany during the 1930s[citation needed] as a network used to communicate within the government.
At the rate of 45.45 (±0.5%) baud — considered speedy at the time — up to 25 telex channels could share a single long-distance telephone channel by using voice frequency telegraphy multiplexing, making telex the least expensive method of reliable long-distance communication.
Canada-wide automatic teleprinter exchange service was introduced by the CPR Telegraph Company and CN Telegraph in July 1957 (the two companies, operated by rivals Canadian National Railway and Canadian Pacific Railway, would join to form CNCP Telecommunications in 1967). This service supplemented the existing international Telex service that was put in place in November 1956. Canadian Telex customers could connect with nineteen European countries in addition to eighteen Latin American, African, and trans-Pacific countries.[18] The major exchanges were located in Montreal (01), Toronto (02), and Winnipeg (03).[19]
In 1958, Western Union started to build a Telex network in the United States.[20] This Telex network started as a satellite exchange located in New York City and expanded to a nationwide network. Western Union chose Siemens & Halske AG,[21] now Siemens AG, and ITT [22] to supply the exchange equipment, provisioned the exchange trunks via the Western Union national microwave system and leased the exchange to customer site facilities from the local telephone company. Teleprinter equipment was originally provided by Siemens & Halske AG [23] and later by Teletype Corporation.[24] Initial direct International Telex service was offered by Western Union, via W.U. International, in the summer of 1960 with limited service to London and Paris.[25]
In 1962, the major exchanges were located in New York City (1), Chicago (2), San Francisco (3), Kansas City (4) and Atlanta (5).[26] The Telex network expanded by adding the final parent exchanges cities of Los Angeles (6), Dallas (7), Philadelphia (8) and Boston (9) starting in 1966.
The Telex numbering plan, usually a six-digit number in the United States, was based on the major exchange where the customer's Telex machine terminated.[27] For example, all Telex customers that terminated in the New York City exchange were assigned a Telex number that started with a first digit "1". Further, all Chicago based customers had Telex numbers that started with a first digit of "2". This numbering plan was maintained by Western Union as the Telex exchanges proliferated to smaller cities in the United States. The Western Union Telex network was built on three levels of exchanges.[28] The highest level was made up of the nine exchange cities previously mentioned. Each of these cities had the dual capability of terminating both Telex customer lines and setting up trunk connections to multiple distant Telex exchanges. The second level of exchanges, located in large cities such as Buffalo, Cleveland, Miami, Newark, Pittsburgh and Seattle, were similar to the highest level of exchanges in capability of terminating Telex customer lines and setting up trunk connections. However, these second level exchanges had a smaller customer line capacity and only had trunk circuits to regional cities. The third level of exchanges, located in small to medium sized cities, could terminate Telex customer lines and had a single trunk group running to its parent exchange.
Loop signaling was offered in two different configurations for Western Union Telex in the United States. The first option, sometimes called local or loop service, provided a 60 milliampere loop circuit from the exchange to the customer teleprinter. The second option, sometimes called long distance or polar was used when a 60 milliampere connection could not be achieved, provided a ground return polar circuit using 35 milliamperes on separate send and receive wires. By the 1970s, and under pressure from the Bell operating companies wanting to modernize their cable plant and lower the adjacent circuit noise that these Telex circuits sometimes caused, Western Union migrated customers to a third option called F1F2. This F1F2 option replaced the DC voltage of the local and long distance options with modems at the exchange and subscriber ends of the Telex circuit.
Western Union offered connections from Telex to the AT&T Teletypewriter eXchange (TWX) system in May 1966 via its New York Information Services Computer Center.[29] These connections were limited to those TWX machines that were equipped with automatic answerback capability per CCITT standard.
In 1970, Cuba and Pakistan were still running 45.5 baud type A Telex.[citation needed] Telex is still widely used in some developing countries' bureaucracies, probably because of its reliability and low cost. The UN asserted at one time that more political entities were reliably available by Telex than by any other single method.
Around 1960[?], some nations began to use the "figures" Baudot codes to perform "Type B" Telex routing.[citation needed]
Telex grew around the world very rapidly. Long before automatic telephony was available, most countries, even in central Africa and Asia, had at least a few high-frequency (shortwave) Telex links. Often these radio links were first established by government postal and telegraph services (PTTs). The most common radio standard, CCITT R.44 had error-corrected retransmitting time-division multiplexing of radio channels. Most impoverished PTTs operated their Telex-on-radio (TOR) channels non-stop, to get the maximum value from them.
The cost of TOR equipment has continued to fall. Although initially specialised equipment was required, many amateur radio operators now operate TOR (also known as RTTY) with special software and inexpensive hardware to adapt computer sound cards to short-wave radios.[30]
Modern "cablegrams" or "telegrams" actually operate over dedicated Telex networks, using TOR whenever required.[citation needed]
[edit] Operation and applications
Telex messages are routed by addressing them to a Telex address, e.g., "14910 ERIC S", where 14910 is the subscriber number, ERIC is an abbreviation for the subscriber's name (in this case Telefonaktiebolaget L.M. Ericsson in Sweden) and S is the country code. Solutions also exist for the automatic routing of messages to different Telex terminals within a subscriber organization, by using different terminal identities, e.g., "+T148".
A major advantage of Telex is that the receipt of the message by the recipient could be confirmed with a high degree of certainty by the "answerback". At the beginning of the message, the sender would transmit a WRU (Who aRe yoU) code, and the recipient machine would automatically initiate a response which was usually encoded in a rotating drum with pegs, much like a music box. The position of the pegs sent an unambiguous identifying code to the sender, so the sender could verify connection to the correct recipient. The WRU code would also be sent at the end of the message, so a correct response would confirm that the connection had remained unbroken during the message transmission. This gave Telex a major advantage over less verifiable forms of communications such as telephone and fax.
The usual method of operation was that the message would be prepared off-line, using paper tape. All common Telex machines incorporated a 5-hole paper-tape punch and reader. Once the paper tape had been prepared, the message could be transmitted in minimum time. Telex billing was always by connected duration, so minimizing the connected time saved money. However, it was also possible to connect in "real time", where the sender and the recipient could both type on the keyboard and these characters would be immediately printed on the distant machine.
Telex could also be used as a rudimentary but functional carrier of information from one IT system to another, in effect a primitive forerunner of Electronic Data Interchange. The sending IT system would create an output (e.g., an inventory list) on paper tape using a mutually agreed format. The tape would be sent by Telex and collected on a corresponding paper tape by the receiver and this tape could then be read into the receiving IT system.
One use of Telex circuits, in use until the widescale adoption of x.400 and Internet email, was to facilitate a message handling system, allowing local email systems to exchange messages with other email and Telex systems via a central routing operation, or switch. One of the largest such switches was operated by Royal Dutch Shell as recently as 1994, permitting the exchange of messages between a number of IBM Officevision, Digital Equipment Corporation All-In-One and Microsoft Mail systems. In addition to permitting email to be sent to Telex addresses, formal coding conventions adopted in the composition of Telex messages enabled automatic routing of Telexes to email recipients.
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