Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information with an immediacy comparable to face-to-face communication. As such, slow communications technologies like postal mail and pneumatic tubes are excluded from the definition. Many transmission media have been used for telecommunications throughout history, from smoke signals, beacons, semaphore telegraphs, signal flags, and optical heliographs to wires and empty space made to carry electromagnetic signals. These paths of transmission may be divided into communication channels for multiplexing, allowing for a single medium to transmit several concurrent communication sessions. Several methods of long-distance communication before the modern era used sounds like coded drumbeats, the blowing of horns, and whistles. Long-distance technologies invented during the 20th and 21st centuries generally use electric power, and include the telegraph, telephone, television, and radio.
Early telecommunication networks used metal wires as the medium for transmitting signals. These networks were used for telegraphy and telephony for many decades. In the first decade of the 20th century, a revolution in wireless communication began with breakthroughs including those made in radio communications by Guglielmo Marconi, who won the 1909 Nobel Prize in Physics. Other early pioneers in electrical and electronic telecommunications include co-inventors of the telegraph Charles Wheatstone and Samuel Morse, numerous inventors and developers of the telephone including Antonio Meucci and Alexander Graham Bell, inventors of radio Edwin Armstrong and Lee de Forest, as well as inventors of television like Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth.
Since the 1960s, the proliferation of digital technologies has meant that voice communications have gradually been supplemented by data. The physical limitations of metallic media prompted the development of optical fibre. The Internet, a technology independent of any given medium, has provided global access to services for individual users and further reduced location and time limitations on communications. (Full article...)
Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz (1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles.
Although an experimental 40-mile (64 km) microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allowed General Bernard Montgomery to remain in continual contact with his group headquarters in London. (Full article...)
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