Encyclopedia
Telegraphy is the long-distance transmission of written messages without physical transport of letters, originally by changing something that could be observed from a distance .
Radiotelegraphy or
wireless telegraphy transmits messages using
radio. Telegraphy includes recent forms of data transmission such as
fax,
email, and
computer networks in general. Wireless telegraphy is also known as CW, for
continuous wave .
Telegraphy messages sent by
telegraph operators using
Morse code were known as
telegrams or
cablegrams, often shortened to
a cable or a
wire message. Later, telegrams sent by the
Telex network, a switched network of
teleprinters similar to the telephone network, were known as
telex messages. 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 e-mail, telegrams were commonly used to create binding legal documents for business dealings.
Wire picture or
wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph.
Optical telegraphs and smoke signals
First telegraph were [optical telegraph]s, including the use of smoke signals and
beacons. These have existed since ancient times. A
semaphore network invented by
Claude Chappe operated in France from 1792 through 1846. It helped
Napoleon enough that it was widely imitated in Europe and the U.S. The last commercial semaphore link left operation 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 , 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 semaphore.
Electrical telegraphs
In 1775 Francisco de Salva offered an electrostatical telegraph. Samuel T. Soemmering 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 used for regular communication the first electromagnetic telegraph in 1833 in
Göttingen.The first commercial
electrical telegraph was constructed by Sir
Charles Wheatstone and Sir William Fothergill Cooke and entered use on the
Great Western Railway. It ran for 13 miles from
Paddington station to West Drayton and came into operation on April 9, 1839. It was
patented in the
United Kingdom in 1837.
In 1843 Scottish physician
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 abbot, Giovanni Caselli, in Italy 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.
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 signalling
alphabet with Morse. America's first telegram was sent by Morse on January 6, 1838, across two miles of wiring. The message read "A patient waiter is no loser." On May 24, 1844, he sent the message, "What hath God wrought?," from Washington to Baltimore, using repeater technology. The Morse/Vail telegraph was quickly deployed in the following two decades.
The first
transatlantic telegraph cable was successfully completed on July 27, 1866, allowing transatlantic telegraph communications for the first time. Earlier submarine cable transatlantic cables installed in 1857 and 1858 only operated for a few days or weeks before they failed. The study of underwater telegraph cables accelerated interest in mathematical analysis of these
transmission lines.
Another advancement in telegraph technology occurred on August 9, 1892, when
Thomas Edison received a patent for a two-way telegraph. He received , "
Duplex Telegraph".
Radiotelegraphy
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. It is considered that
Guglielmo Marconi sent and received his first radio in
Italy up to 6 kilometres in 1896. Around the turn of the century, it is reported that he broadcast signals across the
English Channel and, shortly thereafter, Marconi radiotelegraphed the letter "S" across the
Atlantic Ocean from
England to
Newfoundland.
In 1898 Popov accomplished successful experiments of wireless communication between a naval base and a
battle ship. In 1900 the crew of the Russian battle ship
General-Admiral 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
Gogland island and inside a Russian naval base in
Kotka. Both stations of wireless telegraphy were built under Popov's instructions.
Albert Einstein famously described radiotelegraphy by saying,
- "Wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. And radio operates exactly the same way. The only difference is that there is no cat."
Radiotelegraph proved effective in communication for rescue work when a sea
disaster occurred. Effective communication was able to exist between ships and from ship to shore.
Telegraphic improvements
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.
With the invention of the
teletypewriter, telegraphic encoding became fully automated. Early teletypewriters used
Baudot code, a 5-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 still communicates with Teletype messages over the
SITA or AFTN networks. For example, The
British Airways operations computer system
as of 2004 still used teletype to communicate with other airline computer systems. The same goes for PARS and IPARS that used a similar shifted 6-bit Teletype code, because it requires only 8 bits per character, saving bandwidth and money. A teletype message is often much smaller than the equivalent EDIFACT or XML message.
A
standard timing system developed 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 characters were sent by first sending a "start bit" that pulled the line to the unpowered "space" state. The start bit triggered a wheeled commutator run by a motor with a precise speed . 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. Often, two stop bits were sent to give the mechanism time to finish and stop vibrating.
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". Telex machines first performed rotary-telephone-style pulse dialing, and then sent
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 45.5 bits per second, up to 25 telex channels could share a single long-distance telephone channel, making telex the least expensive method of reliable long-distance communication.
In 1970,
Cuba and
Pakistan were still running 45.5 baud type A telex. Telex is still widely used in some developping countries' bureaucracies, probably because of its low costs and reliability. The
UN asserts that more political entities are 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 telex links. Often these radio links were the first established by government postal and telegraph services . 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 channels non-stop, to get the maximum value from them.
The cost of telex on radio equipment has continued to fall. Although initially specialized equipment was required, many
amateur radio operators now operate TOR with special software and inexpensive adapters from computer sound cards to shortwave radios.
Modern "cablegrams" or "telegrams" actually operate over dedicated telex networks, using TOR whenever required.
In Germany alone, more than 400,000 telex lines remain in daily operation. Over most of the world, more than three million telex lines remain in use.
A major advantage of Telex was 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 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 was sure that he was connected 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 other unreliable 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 reader and paper tape punch. 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 connect 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.
TWX
Almost in parallel with Germany's telex system,
AT&T in the 1930s decided to go telex one better, and began developing a similar service called "Teletype Wide-area eXchange" . AT&T, also known as the Bell system, acquired the
Teletype Corporation in 1930 and used its
teleprinters for TWX.
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 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 deemphasis 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, in order to deliver bananas to the best-paying markets. Communications expanded to UFC's plantations, and were eventually provided to local governments. TRT Telecommunications eventually became the national PTT of many small Central American nations.
- The French Telegraph Cable Company 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 OH 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
As of 2006, most telegraphic messages are carried by the Internet in the form of e-mail.
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.
The Internet was a radical break in three ways. First, it was designed to operate over any digital transmission media. Second, routing was decentralized. Third, large messages were broken into fixed size packets, and then reassembled at the destination. All previous networks had used controlled media, centralized routers and dedicated connections. As the Internet grew, it used progressively faster digital carrier links, employing the digital systems that had been developed for the PSTN.
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 of 32 channels .
Later, SONET and SDH 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."
Currently , 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 10^12 bits per second. No current 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.
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. 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 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 limited to government, academia and other government contractors until the net was opened to commercial use in the 1980s.
In 1992, computer access via modem combined with cheap computers, and graphic point & click interfaces to give a radical alternative to conventional telex systems: personal e-mail.
Individual e-mail accounts were not widely available until local ISPs 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
International Telex remains available via e-mail ports. It is one's e-mail address with numeric or alpha prefixes specifying one's International Record Carrier and account.
Telex has always had a feature called "answerback" that asks a remote machine to send its address. If one is using telex via e-mail, this address is what a remote telex user will want in order to contact an e-mail user.
On January 27, 2006, Western Union of its telegram services; due to the lack of sales. 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, February 3, 2006.
Telegram service in the United States and Canada is still available, operated by International Telegram. Some companies, like Swedish
Telia still deliver telegrams, but they serve as
nostalgic novelty items rather than a primary means of communication. The international telegram service formerly provided by British Telecom has been spun off as an independent company which promotes their use as a retro greeting card or invitation.
In the Netherlands, telegram operations ceased in 2004. In Belgium though, services continue through
Belgacom, most astonishing is that business is still flourishing.
In Japan, NTT provides a telegram 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.
See also
External articles and references
;Citations
;Further reading
- Jeffrey L. Kieve — The Electric Telegraph: a Social and Economic History David and Charles ISBN 0-7153-5883-9
- Tom Standage — The Victorian Internet Berkley Trade, ISBN 0-425-17169-8
;Websites
;Archives
- Archives Center, National Museum of American History, Smithsonian Institution.
- Archives Center, National Museum of American History, Smithsonian Institution.
