Chapter I A: Telecommunication
Telecommunication is the technique of transmitting a message, from one point to another, knowing how much information, if any, is likely to be lost in the process. Hence the term 'telecommunication' covers all forms of distance communications, including radio, telegraphy, television, telephony, data communication and computer networking.
The elements of a telecommunication system are a transmitter, a channel, a line and a receiver. The transmitter is a device that transforms or codes the message into a physical phenomenon called the signal. The transmission channel, by its physical nature, is likely to modify or degrade the signal on its path from the transmitter to the receiver. The receiver has a decoding mechanism capable of recovering the message within certain limits of signal degradation by the communication channel.
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| Alexander Graham Bell |
Bell Labs scientist Claude E. Shannon published A Mathematical Theory of Communication[?] in 1948. This landmark publication was to set the mathematical models used to describe communication systems called information theory. Information theory enables us to evaluate the capacity of a communication channel according to its bandwidth and signal-to-noise ratio.
Visit also: http://www.knowitall.org/kidswork/etv/history/index.html
Telegraph
Telegraphy is the long distance transmission of written messages without physical transport of letters. This definition 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.)
- Before the internet came into general use, telegraphy messages were known as telegrams or cablegrams, often shortened to a cable or a wire message. Telegrams sent by the Telex network, a switched network of teleprinters similar to the telephone network, were known as a telex message. Before long distance telephone services were readily available, telegram services were very popular. Telegrams were often used to confirm business dealings and, unlike e-mail, a telegram is considered a binding legal document 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 facsimilie telegraph. This is why many fax machines have a photo option even today.
The first telegraphs were optical, 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 are faster than smoke signals and beacons and consume no fuel. They are hundreds of times as fast as post riders and serve entire regions. However they require operators and towers every 30 km (20 mi), and only send about two words per minute. This causes them to have a cost per word-mile roughly thirty times as high as electric telegraphs. This is useful to government, but too expensive for most commercial uses other than commodity price information.
The first commercial electrical telegraph constructed by Sir Charles Wheatstone entered use in London in 1838. An electrical telegraph was US-patented in 1842 by Samuel Morse, who also developed the Morse code signalling alphabet, and was quickly deployed in the following two decades. Nikola Tesla and other scientists and inventors showed the usefulness of wireless telegraphy, or radio, beginning in the 1860s.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.
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.
Telephone
The telephone is a telecommunications device which is used to transmit and receive sound (most commonly speech). 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
The telephone handles two kinds of information: signals and voice, at different times on the same twisted pair of wires. The signaling equipment consists of a bell to alert the user of incoming calls, and a dial to enter the phone number for outgoing calls. A calling party wishing to speak to another telephone will pick up the handset, thus operating the switch hook, which puts the telephone into active state or off hook with a resistance short across the wires, causing current to flow.
The telephone exchange detects the DC current, attaches a digit receiver, and sends dial tone to indicate readiness. The user pushes the number buttons, which are connected to a tone generator inside the dial, which generates DTMF tones. The exchange connects the line to the desired line and alerts that line.
When a phone is inactive (on hook), its bell, beeper, flasher or other alerting device is connected across the line through a capacitor. The inactive phone does not short the line, thus the exchange knows it is on hook and only the bell is electrically connected. When someone calls this phone, the telephone exchange applies a high voltage pulsating signal, which causes the sound mechanism to ring, beep or otherwise alert the called party. When that user picks up the handset, the switch hook disconnects the bell, connects the voice parts of the telephone, and puts a resistance short on the line, confirming that the phone has been answered and is active. Both lines being off hook, the signaling job is complete. The parties are connected together and may converse using the voice parts of their telephones.
The voice parts of the telephone are in the handset, and consist of a transmitter (often called microphone) and a receiver. The transmitter, powered from the line, puts out an electric current which varies in response to the acoustic pressure waves produced by the voice. The resulting variations in electric current are transmitted along the telephone line to the other phone, where they are fed into the coil of the receiver, which is a miniature loudspeaker. The varying electric current in the coil causes it to move back and forth, reproducing the acoustic pressure waves of the transmitter.
When a party "hangs up" (puts the handset on the cradle), DC current ceases to flow in that line, thus signaling to the exchange switch to disconnect the telephone call.
History
Credit for inventing the electric telephone remains in dispute. Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell, and Elisha Gray, among others, have all been credited with the invention.
The 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. The Bell and Edison patents, however, were forensically victorious and commercially decisive.
Early development
The following is a brief summary of the legally supported history of the development of the telephone
- 28 December 1871-Antonio Meucci files a patent caveat (n.3335) in the U.S. Patent Office titled "Sound Telegraph", describing communication of voice between two people by wire.
- 1874-Meucci, after having renewed the caveat for two years, fails to find the money to renew it. The caveat lapses.
- 6 April 1875-Bell's U.S. Patent 161,739 "Transmitters and Receivers for Electric Telegraphs" is granted. This uses multiple vibrating steel reeds in make-break circuits.
- 11 February 1876 - Gray invents a liquid transmitter for use with a telephone but does not build one.
- 14 February 1876-Elisha Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
- 14 February 1876-Alexander Bell applies for the patent "Improvements in Telegraphy", for electromagnetic telephones using undulating currents.
- 19 February 1876-Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell's patent application. Gray decides to abandon his caveat.
- 7 March 1876-Bell's U.S. patent 174,465 "Improvement in Telegraphy" is granted, covering "the method of, and apparatus for, transmitting vocal or other sounds telegraphically by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound."
- 30 January 1877-Bell's U.S. patent 186,787 is granted for an electro-magnetic telephone using permanent magnets, iron diaphragms, and a call bell.
- 27 April 1877-Edison files for a patent on a carbon (graphite) transmitter. The patent 474,230 was granted 3 May 1892, after a 15 year delay because of litigation. Edison was granted patent 222,390 for a carbon granules transmitter in 1879.
To fax or faxing is by definition "a method of encoding data, transmitting it over a telephone line or radio broadcast, and receiving a hard copy of the text, line drawings, or photographs at a remote location.
The technology for fax machines was invented a long time, however, fax machines did not become popular with consumers until the 1980s.
Alexander Bain
The first fax machine was invented by Scottish mechanic and inventor Alexander Bain. In 1843, Alexander Bain received a British patent for “improvements in producing and regulating electric currents and improvements in timepieces and in electric printing and signal telegraphs”, in laymen's terms a fax machine.Several years earlier, Samuel Morse had invented the first successful telegraph machine and the fax machine closely evolved from the technology of the telegraph.
The earlier telegraph machine sent morse code (dots & dashes) over telegraph wires that was decoded into a text message at a remote location.
How Did Alexander Bain's Machine Work?
Alexander Bain's fax machine transmitter scanned a flat metal surface using a stylus mounted on a pendulum. The stylus picked up images from the metal surface. An amateur clock maker, Alexander Bain combined parts from clock mechanisms together with telegraph machines to invent his fax machine.
Fax Machine History
Many inventors after Alexander Bain, worked hard on inventing and improving fax machine type devices.
- In 1850, a London inventor named F. C. Blakewell received a patent what he called a "copying telegraph".
- In 1860, a fax machine called the Pantelegraph sent the first fax between Paris and Lyon. The Pantelegraph was invented Giovanni Caselli.
- In 1895, Ernest Hummel a watchmaker from St. Paul, Minnesota invented his competing device called the Telediagraph.
- In 1902, Dr Arthur Korn invented an improved and practical fax, the photoelectric system.
- In 1914, Edouard Belin established the concept of the remote fax for photo and news reporting.
- In 1924, the telephotography machine (a type of fax machine) was used to send political convention photos long distance for newspaper publication. It was developed by the American Telephone & Telegraph Company (AT&T) worked to improve telephone fax technology.
- By 1926, RCA invented the Radiophoto that faxed by using radio broadcasting technology.
- In 1947, Alexander Muirhead invented a very successful fax machine.
- On March 4, 1955, the first radio fax transmission was sent across the continent.
Television was not invented by a single inventor, instead many people working together and alone over the years, contributed to the evolution of television.
See also: Timeline of Television History
Broadcasting Pioneers: The Many Innovators Behind Television History
At the dawn of television history there were two distinct paths of technology experimented with by researchers.Early inventors attempted to either build a mechanical television system based on the technology of Paul Nipkow's rotating disks; or they attempted to build an electronic television system using a cathode ray tube developed independently in 1907 by English inventor A.A. Campbell-Swinton and Russian scientist Boris Rosing.
Electronic television systems worked better and eventual replaced mechanical systems.
Paul Gottlieb Nipkow - Mechanical Television History
German, Paul Nipkow developed a rotating-disc technology to transmit pictures over wire in 1884 called the Nipkow disk. Paul Nipkow was the first person to discover television's scanning principle, in which the light intensities of small portions of an image are successively analyzed and transmitted.John Logie Baird - Mechanical
In the 1920's, John Logie Baird patented the idea of using arrays of transparent rods to transmit images for television. Baird's 30 line images were the first demonstrations of television by reflected light rather than back-lit silhouettes. John Logie Baird based his technology on Paul Nipkow's scanning disc idea and later developments in electronics.Charles Francis Jenkins - Mechanical
Charles Jenkins invented a mechanical television system called radiovision and claimed to have transmitted the earliest moving silhouette images on June 14, 1923.Cathode Ray Tube - Electronic Television History
Electronic television is based on the development of the cathode ray tube, which is the picture tube found in modern TV sets. German scientist, Karl Braun invented the cathode ray tube oscilloscope (CRT) in 1897.Vladimir Kosma Zworykin - Electronic
Russian inventor, Vladimir Zworykin invented an improved cathode-ray tube called the kinescope in 1929. The kinescope tube was sorely needed for television. Zworykin was one of the first to demonstrate a television system with all the features of modern picture tubes.Philo T. Farnsworth - Electronic
In 1927, Philo Farnsworth was the first inventor to transmit a television image comprised of 60 horizontal lines. The image transmitted was a dollar sign. Farnsworth developed the dissector tube, the basis of all current electronic televisions. He filed for his first television patent in 1927 (#1,773,980).Louis Parker - Television Receiver
Louis Parker invented the modern changeable television receiver. The patent was issued to Louis Parker in 1948.Rabbit Ears - Antennae
Marvin Middlemark invented "rabbit ears", the "V" shaped TV antennae. Among Middlemark's other inventions were a water-powered potato peeler and rejuvenating tennis ball machine.Color Television
Color TV was by no means a new idea, a German patent in 1904 contained the earliest proposal, while in 1925 Zworykin filed a patent disclosure for an all-electronic color television system. A successful color television system began commercial broadcasting, first authorized by the FCC on December 17, 1953 based on a system invented by RCA.History of Cable TV
Remote Controls
It was in June of 1956, that the TV remote controller first entered the American home. The first TV remote control called "Lazy Bones," was developed in 1950 by Zenith Electronics Corporation (then known as Zenith Radio Corporation).Origins of Children's Programming
The American Broadcasting Company first aired Saturday morning TV shows for children on August 19, 1950.Plasma TV
The very first prototype for a plasma display monitor was invented in 1964 by Donald Bitzer, Gene Slottow, and Robert Willson.History of Closed Captioning TV
TV closed captions are captions that are hidden in the television video signal, invisible without a special decoder.Web TV
Web TV was rolled out in 1996.Radio
Radio communication was first successfully tested in 1895 by Guglielmo Marconi. He sent a telegraph message without wires, but he didn't send voice over the airwaves; Reginald Fessenden, in 1900, accomplished that. On Christmas Eve, 1906, using his heterodyne principle, Reginald Fessenden transmitted the first radio broadcast in history from Brant Rock Station, Massachusetts[?]. Ships at sea heard a broadcast that included Fessenden playing the song O Holy Night on the violin and reading a passage from the Bible.
The first benefit seen to radio telegraphy was the ability to communicate with ships at sea. A company called British Marconi was established to make use of Marconi's and others' patents. This company along with its subsidiary American Marconi, had a stranglehold on ship to shore communication. It operated much the way American Telephone and Telegraph operated until 1983, owning all of its own equipment and refusing to communicate with non-Marconi equipped ships. Many inventions improved the quality of radio, and amateurs experimented with uses of radio, thus the first seeds of broadcasting were planted.
Audio Broadcasting (1915--)
- Invention of the triode amplifier, generator, and detector enables audio radio
Radio broadcasting is born
Westinghouse in Pittsburgh, Pennsylvania and the Scripps Detroit News in Detroit, Michigan were the first US broadcasters in the early 1920s. Broadcasting was not yet commercially supported; the stations owned by the manufacturers and department stores were established to sell radios and those owned by newspapers to sell newspapers and express the opinions of the owners. Westinghouse was brought into the patent allies group, General Electric, American Telephone and Telegraph, and Radio Corporation of America, and became a part owner of RCA. All radios made by GE and Westinghouse were sold under the RCA label 60% GE and 40% Westinghouse. ATT's Western Electric would build radio transmitters. The patent allies attempted to set up a monopoly, but they failed due to successful competition. Much to the dismay of the patent allies, several of the contracts for inventor's patents held clauses protecting "amateurs" and allowing them to use the patents. Whether the competing manufacturers were really amateurs was ignored by these competitors.
- Commercial (United States) or governmental (Europe) station networks
- Federal Radio Commission
- Federal Communications Commission
- Birth of the soap opera
- Race towards shorter waves and FM
FM radio
VHF television and FM radio both use frequencies on the VHF band. FM radio had been assigned the 42 to 50 MHz band of the spectrum in 1940. The Federal Communications Commission in late 1943 asked the radio manufacturers to establish the Radio Technical Planning Board, which would advise the Federal Communications Commission on allocation and other technical matters. The Radio Technical Planning Board was divided into pannels on various subjects which would make recommendations to the whole board, which the board might support. The Radio Technical Planning Board FM panal recommended that more frequencies should be given to FM in the 50 MHz area where FM was already assigned and operating. Unfortunately for FM and the nearly 400,000 FM receiver owners the Radio Technical Planning Board as a whole did not agree with the panel. The reason the board made this decision was that it had been given flawed evidence by a former Federal Communications Commission engineer named Kenneth Norton. He believed that sunspots, which appear every eleven years, would cause severe disruption to the FM signal. Norton never explained why television signals at the same frequency wouldn't be disrupted. The Radio Technical Planning Board thus recommended that FM radio be relocated near 100 MHz. The Federal Communications Commission heeded the advice of the Radio Technical Planning Board and moved FM to the frequencies between 88 and 106 MHz on June 27, 1945. Later the Federal Communications Commission added the frequencies from 106 to 108 MHz which had been given to facsimile transmission but had never been used for that purpose. This change gave FM radio 100 channels whereas it only had 40 before, it also added to the number of reserved educational stations.
Telegraphy did not go away on radio. Instead, the degree of automation increased. On land-lines in the 1930s, Teletypewriters automated encoding, and were adapted to pulse-code dialing to automate routing, a service called telex. For thirty years, telex was the absolute cheapest form of long-distance communication, because up to 25 telex channels could occupy the same bandwidth as one voice channel. For business and government, it was an advantage that telex directly produced written documents.
Telex systems were adapted to short-wave radio by sending tones over single sideband. CCITT R.44 (the most advanced pure-telex standard) incorporated character-level error detection and retransmission as well as automated encoding and routing.
For many years, telex-on-radio (TOR) was the only reliable way to reach some third-world countries. TOR remains reliable, though less-expensive forms of e-mail are displacing it. Many national telecom companies historically ran nearly pure telex networks for their governments, and they ran many of these links over short wave radio.
Internet Radio (1995--)
The term "internet radio" is a misnomer: its consists of putting out radio-style audio programming over streaming Internet connections: no radio transmitters need be involved at any point in the process.
- Early technology wars: Push or pull, streaming media or multicast
- Run your own station with http://www.live365.com/ or almost like Geocities or Hotmail
Satellite Radio (2001--)
In 1973 martin copper came up with Motorola. He took the project and let the people of New York see it. In 1977 the first cell phone was made in Chicago . When it first came out 2000 people was given a free trial. Then other places started to make cell phones. When to cell phone first came out they were huge. The people did not know how to make the phone any more compact. In 1988 the big company's started to make cell phones. There were over 54 places all over the world.
The future of cell phones
From the year 1843 to now phones have changes a lot. in the year to come they will change more. The numbers will change . They will be the your social security number. This will change because the states numbers are getting mixed up. This will also change because different people have the same numbers. In the year 2010 you will be able to search the internet for what every on the phone. This is now happening but in the future in will become more advanced. Now the cell phone companies are trying to get the house phone companies to shut down.
How do cell phones work?
Cell phone are getting harder and harder to use. The only thing that people need to know how to do is call some one and to store numbers. This is not how the cell phone companies think. They think that you need text message, car phone, radio phone, and that you need 25 different channel on a phone . I could see if it was on TV. but its not. all you need to know how to call the number. All that you really need to know about working cell phone is how to dial the numbers.
GSM
GSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.
Mobile services based on GSM technology were first launched in Finland in 1991. Today, more than 690 mobile networks provide GSM services across 213 countries and GSM represents 82.4% of all global mobile connections. According to GSM World, there are now more than 2 billion GSM mobile phone users worldwide. GSM World references China as "the largest single GSM market, with more than 370 million users, followed by Russia with 145 million, India with 83 million and the USA with 78 million users."
Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries. SIM cards (Subscriber Identity Module) holding home network access configurations may be switched to those will metered local access, significantly reducing roaming costs while experiencing no reductions in service.
GSM, together with other technologies, is part of the evolution of wireless mobile telemmunications that includes High-Speed Circuit-Switched Data (HSCSD), General Packet Radio System (GPRS), Enhanced Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service (UMTS).
CDMA
What is Code-Division Multiple Access (CDMA)?
Also see CDMA One, CDMA2000, and W-CDMA.
CDMA (Code-Division Multiple Access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.
CDMA employs analog-to-digital
conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes, which enhances privacy and makes cloning difficult.
The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff, which minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes supports several times as many signals per unit bandwidth as analog modes. CDMA is compatible with other cellular technologies; this allows for nationwide roaming.
The original CDMA standard, also known as CDMA One and still common in cellular telephones in the U.S., offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and Wideband CDMA deliver data many times faster.
GSM
GSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.
Learn More
Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries. SIM cards (Subscriber Identity Module) holding home network access configurations may be switched to those will metered local access, significantly reducing roaming costs while experiencing no reductions in service.
GSM, together with other technologies, is part of the evolution of wireless mobile telemmunications that includes High-Speed Circuit-Switched Data (HSCSD), General Packet Radio System (GPRS), Enhanced Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service (UMTS).
CDMA
What is Code-Division Multiple Access (CDMA)?
Also see CDMA One, CDMA2000, and W-CDMA.
CDMA (Code-Division Multiple Access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.CDMA employs analog-to-digital
conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes, which enhances privacy and makes cloning difficult.
The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff, which minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes supports several times as many signals per unit bandwidth as analog modes. CDMA is compatible with other cellular technologies; this allows for nationwide roaming.
The original CDMA standard, also known as CDMA One and still common in cellular telephones in the U.S., offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and Wideband CDMA deliver data many times faster.
 | Getting started with CDMA |
| To explore how CDMA is used in the enterprise, here are additional resources: |
| CDMA and GSM: What's the difference?: The differences between the two competing cell phone technologies are discussed in this article. The piece was inspired by a Brighthand.com reader's question. |
| 3G: The CDMA alternative : CDMA2000 is a third-generation (3G) mobile wireless technology that can support mobile data communications at speeds ranging from 144 Kbps to 2 Mbps. This column discusses the history and specifications of CDMA and explores its benefits. |
| Ericsson's Nortel LTE, CDMA win gives it 4G advantage: Ericsson's winning bid for Nortel's CDMA and LTE business gives it a launchpad into the early North American 4G market and leaves loser Nokia Siemens Networks in a tricky position. |
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