Telephones and Telegraphs [2]
Webpages concerning "Telephones and Telegraphs [2]"
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Wikipedia-Article "Telephones"
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This article is about telephone technology. For the game of telephone, see Telephone (game). For the band, see Téléphone.
The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. Most telephones operate through transmission of electric signals over a complex telephone network which allows almost any phone user to communicate with almost any other.
Introduction
There are four principal means by which an end user using a telephone handset may connect to a telephone network: a traditional fixed phone "landline", which uses dedicated physical wire connections connected to a single location; wireless and radio telephones, which use either analog or digital radio signals; satellite telephones, which utilize telecommunications satellites; and voice over internet protocol (VoIP) telephones, which use broadband internet connections.
Between end users, transmissions across a network may be carried by fiber optic cable, point to point microwave or satellite relay.
Until relatively recently, a "telephone" generally referred only to landlines. Cordless and mobile phones are now common in many places around the world, with mobile phones expected to gradually displace the conventional landline telephone. Unlike a mobile phone, a cordless telephone is considered to be landline because it is only useable within a short distance of a small personal or domestic base station connected to a fixed phone line.
The identity of the inventor of the electric telephone remains in dispute. Antonio Meucci, Johann Philipp Reis, and Alexander Graham Bell, amongst others, have all been credited with the invention.
History
The very early history of the telephone is a confusing morass of claim and counterclaim, which was not clarified by the huge mass of lawsuits which hoped to resolve the patent claims of individuals. There was a lot of money involved, particularly in the Bell Telephone companies, and the aggressive defense of the Bell patents resulted in much confusion. Additionally, the earliest investigators preferred publication in the popular press and demonstration to investors instead of scientific publication and demonstration to fellow scientists.
It is important to note that there is probably no single "inventor of the telephone". The modern telephone is the result of work done by many hands, all worthy of recognition of their addition to the field.
- Further information: Timeline of the telephone & Invention of the telephone
Early development
The following is a brief summary of the history of the invention of the telephone:
- 1849 Antonio Meucci, an Italian living in Havana, demonstrates a device later called a telephone. (The demonstration involves direct electrical connections to people.)
- 1854 Charles Bourseul publishes a description of a make-break telephone transmitter and receiver but does not construct a working instrument.
- 1854 Meucci demonstrates an electric telephone in New York. [1]
- 1860 Johann Philipp Reis demonstrates a make-break transmitter after the design of Bourseul.
- 1860 Meucci supposedly demonstrates his telephone on Staten Island.
- 1861 Reis manages to transfer voice electrically over a distance of 340 feet, see Reis' telephone.
- 1871 Meucci files a patent caveat (a statement of intention to patent).
- 1872 Elisha Gray founds Western Electric Manufacturing Company.
- July 1873 Thomas Alva Edison notes variable resistance in carbon grains due to pressure, but shelves the discovery.
- 1874 Gray demonstrates his liquid transmitter telephone at the Highland Park Presbyterian Church.
- 2 June 1875 Alexander Graham Bell first transmits voice.
- 1 July 1875 Bell first uses a bi-directional capable telephone (Both the transmitter and the receiver were identical membrane instruments.)
- 14 February 1876 Bell files his first patent on the telephone.
- Two hours later Gray files his patent caveat.
- 30 January 1877 Bell patents the electro-dynamic transmitter, receiver telephone telephone
Later history
The history of additional inventions and improvements of the electrical telephone includes the carbon microphone (later replaced by the electret microphone now used in almost all telephone transmitters), the manual switchboard, the rotary dial, the automatic telephone exchange, the computerized telephone switch, Touch Tone® dialing (DTMF), and the digitization of sound using different coding techniques including pulse code modulation or PCM (which is also used for .WAV files and compact discs).
Newer systems include IP telephony, ISDN, DSL, mobile cellular phone systems, cordless telephones, and the third generation cell phone systems that promise to include high-speed packet data transfer.
The industry has divided into telephone equipment manufacturers and telephone network operators (telcos). Operating companies often hold a national monopoly. In the United States, the Bell System was vertically integrated. It fully or partially owned the telephone companies that provided service to about 80% of the telephones in the country and also owned Western Electric, which manufactured or purchased virtually all the equipment and supplies used by the local telephone companies. The Bell System divested itself of the local telephone companies in 1984 in order to settle an antitrust suit brought against it by the United States Department of Justice.
In 1926 Bell Labs and the British Post Office engineered the first two-way conversation across the Atlantic.
The first commercial transatlantic telephone call was between New York City and London and occurred on January 7, 1927.
Digital Telephony
The Public Switched Telephone Network (PSTN) has gradually evolved towards digital telephony which has improved the capacity and quality of the network. End-to-end analog telephone networks were first modified in the 1970s by upgrading long-haul transmission networks with SONET technology and fiber optic transmission methods. Digital transmission made it possible to carry multiple digitized switched circuits on a single transmission medium (known as multiplexing). While today the end instrument remains analog, the analog signals reaching the aggregation point (Serving Area Interface (SAI) or the central office (CO) ) are typically converted to digital signals. Digital loop carriers (DLC) are often used, placing the digital network ever closer to the customer premises, relegating the analog local loop to legacy status.
Wireless phone systems
While the term "wireless" means radio and can refer to any telephone that uses radio waves it is primarily used for cell phones. In the United States wireless companies tend to use the term wireless to refer to a wide range of services while the cell phone itself is called a mobile phone, mobile, cell phone or simply cell with the trend now moving towards mobile.
The changes in terminology is partially due to providers using different terms in marketing to differentiate newer digital services from older analog systems and services of one company from another.
An additional term which could rebound into English is "handy," formed by Germans as slang from the English word. Native English-speakers do not understand this word for "mobile phone."
Cordless telephone
Cordless telephones, first invented by Teri Pall in 1965, consist of a base unit that connects to the land-line system and also communicates with remote handsets by low power radio. This permits use of the handset from any location within range of the base. Because of the power required to transmit to the handset, the base station is powered with an electronic power supply. Thus, cordless phones typically do not function during power outages. Initially, cordless phones used the 1.7 MHz frequency range to communicate between base and handset. Because of quality and range problems, these units were soon superseded by systems that used frequency modulation (FM) at higher frequency ranges (49 MHz, 900 MHz, 2.4 GHz, and 5.8 GHz). The 2.4 GHz cordless phones can interfere with certain wireless LAN protocols (802.11b/g) due to the usage of the same frequencies. On the 2.4 GHz band, several "channels" are utilized in an attempt to guard against degradation in the quality of the voice signal due to crowding. The range of modern cordless phones is normally on the order of a few hundred meters.
Cellular phone
Modern mobile phone systems are cell-structured. Radio is used to communicate between a handset and nearby cell sites.
When a handset gets too far from a cell site, a computer system commands the handset and a closer cell site to take up the communications on a different channel without interrupting the call.
Radio frequencies are a limited, shared resource. The higher frequencies used by cell phones have advantages over short distances. Connection distance is somewhat predictable and can be controlled by adjusting the power level. By only using enough power to connect to the "nearest" cell site phones using one cell site will cause almost no interference with phones using the same frequencies on another cell site. The higher frequencies also work well with various forms of multiplexing which allows more than one phone to connect to the same tower with the same set of frequencies.
Cordless/mobile phone
There are phones that work as a cordless phone when near their corresponding base station (and sometimes other base stations) and work as a wireless phone when in other locations but for a variety of reasons did not become popular.
Some kinds of cordless phones work like cellular phones but only within a small private network covering a building or group of buildings. These kinds of systems using VoIP are popular in hospitals and factories where the same wireless network can be used for both data and voice.
VoIP Telephony
Also known as Internet telephony or Voice over IP (VoIP), digital telephony is a disruptive technology that is rapidly replacing traditional telephone networks. In Japan and Korea up to 10% of subscribers, as of January 2005, have switched from analog to digital telephone service. A recent Newsweek article suggested that Internet telephony may be "the next big thing." [2]
Digital telephones use a broadband Internet connection to transmit conversations as data packets. In addition to replacing the PSTN, digital telephony is also competing with mobile phone networks by offering free or lower cost connections via WiFi hotspots. As mentioned above VoIP is also used on private wireless networks which may or may not have a connection to the outside telephone network.
Telephone equipment research labs
Bell Labs is a noted telephone equipment research laboratory, amongst its other research fields.
Telephone operating companies
In some countries, many telephone operating companies (commonly abbreviated to telco) are in competition to provide telephone services. Some of them include those in the following list. However, the list only includes providers of copper wires from the exchange to the user, not those who only supply "Voice over IP" or only transport voice signals between exchanges. See also: List of telephone operating companies
Trivia
- The modern handset came into existence when a Swedish lineman tied a microphone and earphone to a stick so he could keep a hand free.
- The folding portable phone was an intentional copy of the fictional futuristic communicators (which in use actually more closely resembled walkie-talkies, Nextel-style) used in the television show Star Trek.
See also
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Telephone equipment |
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Telephone equipment manufacturersSeveral manufacturers build telephones of all kinds. Some of these are:
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Telephone technology
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Telephone system, organization, and structure
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Telephone hacking and exploitation |
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US-specific terminology |
Patents
- US174465 -- Telegraph -- A. G. Bell
- US3449750 -- Duplex Radio Communication and Signalling Appartus -- G. H. Sweigert
References
- Huurdeman, Anton A. (2003). The Worldwide History of Telecommunications, IEEE Press and J. Wiley & Sons, 2003. ISBN 0471205052
Wikipedia-Article "Telegraphs [2]"
- Telegram redirects here. For other uses of the word "telegram", see telegram (disambiguation).
Telegraphy (from the Greek words tele = far and graphein = write) is the long-distance transmission of written messages without physical transport of letters, originally over wire. Radiotelegraphy or wireless telegraphy transmits messages using radio. As Albert Einstein put it, "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." 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).
- 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.
- Before fax machines came into general use, wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. This is why many fax machines have a photo option even today.
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Optical telegraphs and smoke signals
The first telegraphs were optical telegraphs, 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 (Swedish) 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 (20 mi), and only send 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 thirty-fold compared to semaphore.
Electrical telegraphs
The first electromagnetic telegraph was created by Baron Schilling in 1832. 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.
An electrical telegraph was independently developed and patented in the United States in 1837 by Samuel Morse. He developed the Morse code signalling alphabet with his assistant, Alfred Vail. 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.
In 1867, David Brooks (while working for the Central Pacific Railroad) was awarded U.S. Patent 63,206 (March 26) and U.S. Patent 69,622 (October 9) for his improvements to telegraph insulators. He was also awarded reissue number 2,717 on August 6, 1867, for U.S. Patent 45,221, which was originally awarded to him on November 29, 1864, for his insulator design. Brooks' patents allowed the Central Pacific to more easily communicate with construction crews building the First Transcontinental Railroad in America; the completion of the railroad was broadcast by telegraph on May 10, 1869, with the telegrapher striking his key in unison with the strikes on the Golden Spike during the completion ceremony.
Another advancement in telegraph technology occurred on August 9, 1892, when Thomas Edison received a patent for a two-way 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 demostrated to wide public his receiver of wireless telegraphy signals, called lightning detector, on May, 7 of 1895. In 1898 Popov accomplished successful experiments of communication by wireless telegraphy between naval base and a battle ship. In 1900 crew of 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 Russian naval base. Both stations of wireless telegraphy were built under Popov's instructions. Is is also considered that Guglielmo Marconi sent and received his first radio signal in Italy in 1895. By 1899 he did it across the English Channel and in 1902 he radiotelegraphed the letter "S" across the Atlantic Ocean from England to Newfoundland.
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 (FICO) as of 2004 still used teletype to communicate with other airline computer systems. The same goes for PARS (Programmable Airline Reservation System) 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 "space" 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 "mark state". 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 "space 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 performing reliable long-distance communication.
In 1970 Cuba and Pakistan were still running 45.5 baud type A telex. Telex is still widely used in third-world bureaucracies, probably because of its low costs. The UN asserts that more political entities are reliably available by telex than by any other single method.
Many dictatorships that cut off telephone, fax and internet services, leave existing telex networks in place. This enables bureaucratic departments to communicate with each other, but also allows for easy communication control on the part of the dictatorship, since any wiretap automatically generates complete transcripts.
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 telex on radio (TOR) equipment has continued to fall. Many amateur radio operators 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.
TWX
Almost in parallel with Germany's telex system, Bell Labs in the 1930s decided to go telex one better, and began developing a similar service (with pulse dialing among other features) called "Teletype Wide-area eXchange" (TWX).
TWX originally ran 75 bits per second, sending Baudot code and dial selection. However, Bell developed a second generation of "four row" modems called the "Bell 101 dataset", which is the direct ancestor of the Bell 103 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.
The "four row" TWX service had "control characters" that let the machine behave like office typewriters. These provided paragraph indentation, form feeds, and other services that were never available with Baudot codes. However, the TWX code only used 93 of 128 characters.
The Teletype Corporation was founded by Edward E. Kleinschmidt. It had the cheapest teletypewriters that could be adapted to the TWX code. Bell purchased the corporation to assure its supply of "model 33" TWX teletypewriters.
The model 33 was the cheapest teletypewriter available for use with computers. Computer people, of course, wanted a full set of characters. Teletype provided them.
ASCII was born from TWX code. It was formalized as CCITT international alphabet 5. Careful study will show that ASCII traces many character codes back to Baudot, which in turn traces some characters back to manual telegraphy.
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 (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 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
Around 1965, in a radical break with existing standards, DARPA commissioned a study of decentralized switching systems, hoping to find something more advanced than TOR that could still hope to survive a nuclear war. 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 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, using the digital systems which 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 (E-1) of 32 channels (with one channel for frame synchronisation).
E-mail starts to displace 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 (UUNET, the Well, GEnie, DECNET) 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 IRC 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.
Some companies, like Western Union and Swedish Telia still deliver Telegrams, but they serve as nostalgic novelty items rather than a primary means of communication.