Telecommunications is what developed
the world today. Anything radio,
signalling or anything that starts in “Tele”
is a part of Telecommunications,
even computers. A well known founder of Telecommunications is Alexander graham
Early forms of Telecommunication include smoke signals and drums. Drums were used by natives in Africa, New Guinea and South America whereas smoke signals were used by natives in North America and China. In the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "The enemy has been sighted" had to be agreed upon in advance.
In 1792, Claude Chappe, a French engineer, built the first fixed visual Telegraphy system (or semaphore line) between Lille and Paris. However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres (six to nineteen miles). As a result of competition from the electrical Telegraph, the last commercial line was abandoned in 1880.
Telecommunication system consists of three basic elements:
Ø a transmitter that takes information and converts it to a signal;
Ø a transmission medium that carries the signal; and,
Ø a receiver that receives the signal and converts it back into usable information.
The first commercial electrical Telegraph was constructed by Sir Charles Wheatstone and Sir William Fothergill Cooke and opened on 9 April 1839. Both Wheatstone and Cooke viewed their device as "an improvement to the [existing] electromagnetic Telegraph" not as a new device.
Samuel Morse independently developed a version of the electrical Telegraph that he unsuccessfully demonstrated on 2 September 1837. His code was an important advance over Wheatstone's signaling method. The first transatlantic Telegraph cable was successfully completed on 27 July 1866, allowing transatlantic Telecommunication for the first time.
The conventional Telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849. However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to “hear” what was being said. The first commercial Telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London.
Wireless refers to a communications system in which waves carry a signal through air rather than through a wire. Most wireless systems use radio frequency (RF) or infrared (IR) waves.
The first "wireless" instrument was the wireless Telegraph, invented the early 20th century. This later came to be known as radio when amplitude modulation (AM), made it possible to transmit voice and music via wireless. Today, wireless devices are being developed to serve various Telecommunications markets, such as paging services, personal communications service (PCS), cellular Telephone service (CTS), low earth orbiting satellite networks (LEOs), 2-way radios and more.
Although some of these technologies such as paging services have been around for over a decade, others such as LEOs are relatively new and are still in development. Before cellular Telephones were available in 1984, mobile phones were the only way one could place a call from a car. These were costly with a limited capacity due to only one transmitter and receiver available for the entire area. There was also considerable static. A mobile radio service is ½ duplex, which means that although it is a 2-way communication, only one person can transmit while the other person receives at any one time. Mobile operators can contact each other, but not anyone from a public network, or a service not their own. Mobile services were popular with taxicabs, police departments and fire departments.
In order for wireless systems to work, the waves are transmitted on a radio frequency. Frequency refers to the number of times a radio wave completes a cycle in a second. Different companies use different portions of the spectrum to communicate with wireless radio service. Due to the fact that there are a limited amount of radio frequencies available, the FCC allocates frequencies. This is to stop different companies transmitting over the same frequency. For example, 2 radio channels transmitting over the same frequency would result in listeners hearing an overlap of broadcasts. This is why the FCC breaks up the spectrum and assigns the frequencies. The higher the frequency is the smaller the wave. Higher frequencies are more susceptible to weather conditions like rain since raindrops are larger in comparison to a smaller wave. That very raindrop is smaller in comparison to a larger wave. Lower frequencies are not as affected by weather conditions