Telegraphy

This article is about telegraphy in general. For the Electrical telegraph, see Electrical telegraph.

Claude Chappe's optical telegraph on the Litermont near Nalbach, Germany

Telegraphy (from the Greek words tele (τηλε) = far and graphein (γραφειν) = write) is the long-distance transmission of written messages without physical transport of letters. Radiotelegraphy or wireless telegraphy transmits messages using radio. Telegraphy includes recent forms of data transmission such as fax, email, and computer networks in general.

A telegraph is a machine for transmitting and receiving messages over long distances, i.e., for telegraphy. The word telegraph alone 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 using a spark gap.

A telegraph message sent by a telegraph operator (or telegrapher) using Morse code was known as a telegram or cablegram, often shortened to a cable or a wire message. Later, a telegram sent by the Telex network, a switched network of teleprinters similar to the telephone network, was known as a telex message.

Before long distance telephone services were readily available or affordable, telegram services were very popular. Telegrams were often used to confirm business dealings and, unlike email, telegrams were commonly used to create binding legal documents for business dealings.

A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph.

Optical

The first telegraphs came in the form of optical telegraphs, including the use of smoke signals and beacons, which have existed since ancient times. A semaphore network invented by Claude Chappe operated in France from 1792 through 1846. It helped Napoleon enough to be widely imitated in Europe and the U.S. 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 and smoke signals, they were dependent on good weather to work. 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.

Some 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. To people who are only aware of the electrical telegraph, the reason for this name will be obscure.

Electrical telegraphs

Main article: Electrical telegraph

Samuel Thomas von Sömmering constructed his electrochemical telegraph in 1809. Also as one of the first, an electromagnetic telegraph was created by Baron Schilling in 1832. Carl Friedrich Gauss and Wilhelm Weber built and first used for regular communication the electromagnetic telegraph in 1833 in Göttingen. The first commercial electrical telegraph was constructed by Sir William Fothergill Cooke 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 April 1839. It was patented in the United Kingdom in 1837. 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.

A morse key

The famous telegram sent by Samuel F. B. Morse from the Capitol in Washington to Alfred Vail in Baltimore in 1844: "What hath God wrought"

An electrical telegraph was independently developed and patented in the United States in 1837 by Samuel F. B. Morse. His assistant, Alfred Vail, developed the Morse code signaling alphabet with Morse. America's first telegram was sent by Morse on January 6, 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 May 24, 1844, he sent the message "What hath God wrought" (quoting Numbers 23:23) from the Old Supreme Court Chamber in the Capitol in Washington to the old Mt. Clare Depot in Baltimore. This message was chosen by Annie Ellsworth of Lafayette, Indiana, later Mrs. Roswell Smith (Roswell, NM was named after her husband), the daughter of Patent Commissioner Henry Leavitt Ellsworth. The Morse/Vail telegraph was quickly deployed in the following two decades.

The first commercially successful transatlantic telegraph cable was successfully completed on 18 July 1866. 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).

Major telegraph lines in 1891

Australia was first linked to the rest of the world in October 1872 by a submarine telegraph cable at Darwin. This brought news reportage from the rest of the world. (Conley, David and Lamble, Stephen (2006) The Daily Miracle: An introduction to Journalism,(Third Edition) Oxford University Press, Australia pp. 305-307).

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. Edison filed for a US patent on the duplex telegraph on Sept 1, 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.

Wireless telegraphy

Main article: 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 receiver of wireless signals, also used as a lightning detector, on 7 May 1895.

Guglielmo Marconi sent and received his first radio signal in Italy up to 6 kilometres in 1896. On May 13 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. 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 the 11th and 12th of 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 defence 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.

Telegraphic improvements

Teletype machines in World War II

A continuing goal in telegraphy has been to reduce the cost per message by reducing hand-work, or increasing the sending rate. 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 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 still used teletype to communicate with other airline computer systems. The same goes for PARS (Programmed Airline Reservation System) 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.

Telex

A Siemens T100 Telex machine

A late-model British Telecom "Puma" telex machine, circa 1980s

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". 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. The network was used to communicate within the government.

At the then-blinding rate of 45.45 (±0.5%) baud, 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 rival 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. The major exchanges were located in Montreal (01), Toronto (02), Winnipeg (03).

In 1958, Western Union Telegraph Company started to build a telex network in the United States. 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,now Siemens AG, and ITT 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 and later by Teletype Corporation. 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.

In 1962, the major exchanges were located in New York City (1), Chicago (2), San Francisco (3), Kansas City (4) and Atlanta (5). 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. 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. 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 TWX system in May 1966 via its New York Information Services Computer Center. 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. 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.

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 the 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.

Modern "cablegrams" or "telegrams" actually operate over dedicated Telex networks, using TOR whenever required.

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 was (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 minimising 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.

TWX originally ran 75 bits per second, sending Baudot code and dial selection. However, Bell later developed a second generation of "four row" modems called the "Bell 101 dataset", which is the direct ancestor of the Bell 103 modem that launched computer time-sharing. The 101 was revolutionary, because it ran on ordinary subscriber lines that could (at the office) be routed to special exchanges called "wide-area data service". Because it was using the public switched telephone network, TWX had special area codes: 510, 610, 710, 810 and 910. With the demise of TWX service, these codes were re-provisioned as standard geographic NPAs in the 1990s.

Bell's original consent agreement limited it to international dial telephony. Western Union Telegraph Company had given up its international telegraphic operation in a 1939 bid to monopolize U.S. telegraphy by taking over ITT's PTT business. The result was de-emphasis on telex in the U.S. and a cat's cradle of small U.S. international telex and telegraphy companies. These were known by regulatory agencies as "International Record Carriers".

• Western Union Telegraph Company developed a spinoff called "Cable System". Cable system later became Western Union International.
• ITT's "World Communications" was amalgamated from many smaller companies: "Federal Telegraph", "All American Cables and Radio", "Globe Wireless", and a common carrier division of Mackay Marine.
• RCA communications had specialised in crossing the Pacific. It later joined with Western Union International to become MCI.
• Before World War I, Tropical Radiotelegraph put radio telegraphs on ships for its owner, The United Fruit Company, to enable them to deliver bananas to the best-paying markets. Communications expanded to UFC's plantations, and were eventually provided to local governments. TRT Telecommunications (as it is now known) eventually became the national PTT of many small Central American nations.
• The French Telegraph Cable Company (owned by French investors) had always been in the U.S. It laid cable from the U.S. to France. It was formed by "Monsieur Puyer-Quartier". This is how it got its telegraphic routing ID "PQ".
• Firestone Rubber developed its own IRC, the "Trans-Liberia Radiotelegraph Company". It operated shortwave from Akron, Ohio to the rubber plantations in Liberia. TL is still based in Akron.

Bell telex users had to select which IRC to use, and then append the necessary routing digits. The IRCs converted between TWX and Western Union Telegraph Co. standards.

Arrival of the Internet

Around 1965, DARPA commissioned a study of decentralized switching systems. Some of the ideas developed in this study provided inspiration for the development of the ARPANET packet switching research network, which later grew to become the public Internet.

As the PSTN became a digital network, T-carrier "synchronous" networks became commonplace in the U.S. A T-1 line has a "frame" of 193 bits that repeats 8000 times per second. The first bit, called the "sync" bit, alternates between 1 and 0 to identify the start of the frames. The rest of the frame provides 8 bits for each of 24 separate voice or data channels. Customarily, a T-1 link is sent over a balanced twisted pair, isolated with transformers to prevent current flow. Europeans adopted a similar system (E-1) of 32 channels (with one channel for frame synchronisation).

Later, SONET and SDH (the synchronous digital hierarchy) were adapted to combine carrier channels into groups that could be sent over optic fiber. The capacity of an optic fiber is often extended with wavelength division multiplexing, rather than rerigging new fibre. Rigging several fibres in the same structures as the first fibre is usually easy and inexpensive, and many fibre installations include unused spare "dark fibre", "dark wavelengths", and unused parts of the SONET frame, so-called "virtual channels."

As of 2006, the fastest well-defined communication channel used for telegraphy is the SONET standard OC-768, which sends about 40 gigabits per second.

The theoretical maximum capacity of an optic fiber is more than 10¹² bits (one terabit or one trillion bits) per second. No current (2006) encoding system approaches this theoretical limit, even with wavelength division multiplexing.

Since the Internet operates over any digital transmission medium, further evolution of telegraphic technology will be effectively concealed from users.

As of 2007, most telegraphic messages are carried by the Internet in the form of e-mail.

E-mail displaces telegraphy

E-mail was first invented for Multics in the late 1960s. At first, e-mail was only possible between different accounts on the same computer (typically a mainframe). UUCP allowed different computers to be connected to allow e-mails to be relayed from computer to computer. With the growth of the Internet, e-mail began to be possible between any two computers with access to the Internet.

Various private networks (UUNET, the Well, GEnie) had e-mail from the 1970s, but subscriptions were quite expensive for an individual, $25 to $50 a month, just for e-mail. Internet use was then largely limited to government, academia and other government contractors until the net was opened to commercial use in the 1980s.

By the early 1990s, modems made e-mail a viable alternative to telex systems in a business environment. But individual e-mail accounts were not widely available until local Internet service providers were in place, although demand grew rapidly, as e-mail was seen as the Internet's killer app. The broad user base created by the demand for e-mail smoothed the way for the rapid acceptance of the World Wide Web in the mid-1990s.

Telegraphy as a legacy system

Western Union announced the discontinuation of all of its telegram services effective from 31 January 2006. Only 20,000 telegrams were sent in 2005, compared with 20 million in 1929. According to Western Union, which still offers money transfer services, its last telegram was sent Friday, 27 January 2006. The company stated that this was, "... the final transition from a communications company to a financial services company."

Telegram service in the United States and Canada is still available, operated by iTelegram and Globegram. Some companies, like Swedish Telia still deliver telegrams, but these telegrams serve as nostalgic novelty items rather than a primary means of communication.

In the Netherlands, telegram operations ceased in 2004. On 9 February 2007, according to the online edition of the Telegraaf newspaper, the Netherlands national telecommunications company KPN pulled the plug on the last Telex machine in the Netherlands after having operated a Telex network since 1933. Citing the fact that they only had 200 customers for its Telex service remaining, it was decided that it was no longer worthwhile to continue to offer Telex within the Netherlands. It is, however, still possible to send Telex messages to foreign customers through the Internet. In Belgium though, services continue through Belgacom. In this case, however, business is flourishing; many telegrams are sent every day.

In Japan, NTT provides a telegram (denpou) service that is today used mainly for special occasions such as weddings, funerals, graduations, etc. Local offices offer telegrams printed on special decorated paper and envelopes.

In New Zealand, while general public use telegrams have been discontinued, a modern variant has arisen for businesses, mainly utilities and the like, to send urgent confidential messages to their customers, leveraging off the perception that these are important messages. New Zealand Post describes the service as " a cost effective debt collection tool designed to help you to recover overdue money from your customers. New Zealand Post Telegrams are delivered by a courier in a Telegram branded envelope on Telegram branded paper. This has proven to be an effective method to spur customers into immediate action".

In the United Kingdom, the international telegram service formerly provided by British Telecom has been spun off as an independent company which promotes the use of telegrams as a retro greeting card or invitation.

In Australia, Australia Post offers the TELeGRAM service - "The TELeGRAM combines new age demands with old world charm to offer you a quick, convenient way to send a message that matters." Messages can be submitted online or by telephone, and can be printed on a range of template designs. The printed telegrams are dispatched using Express Post Mail Service or the Ordinary Mail Service. Orders received before 15:00 are dispatched on the same day. The cost of the service, being AUD4.50 for Ordinary and AUD8.50 for Express Post Mail Services in comparison with AUD0.50 for an Australia-wide postage fee, makes this service too expensive for day-to-day communication.

See also

• Telegram style The concise written style developed for use in a telegram.
• David E. Hughes designed a telegraph that used an alphabetic keyboard and printer wheel in 1856.

References

Further reading

• Jeffrey L. Kieve — The Electric Telegraph: a Social and Economic History David and Charles (1973) ISBN 0-7153-5883-9
• Tom Standage — The Victorian Internet Berkley Trade, (1998) ISBN 0-425-17169-8
• The Old Telegraphs, Geoffrey Wilson, Phillimore & Co Ltd 1976 ISBN 0900592796
• The Railway Telegraph, Dargan, J, Australian Railway Historical Society Bulletin, March, 1985 pp49-71

External links

• The Porthcurno Telegraph Museum The biggest Telegraph station in the world, now a museum
• History of the U.S. Telegraphic Industry from Economic History.net
• Distant Writing - The History of the Telegraph Companies in Britain between 1838 and 1868
• Era Ends: Western Union Stops Sending Telegrams
• Royal Engineers Museum — Telegraph Services
• Anglo-American Telegraph Company, Ltd. Records, 1866 – 1947 Archives Center, National Museum of American History, Smithsonian Institution.
• Western Union Telegraph Company Records, 1820–1995 Archives Center, National Museum of American History, Smithsonian Institution.
• Early telegraphy and fax engineering, still operable in a German computer museum
• NASA - Carrington Super Flare NASA May 6 2008