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The History of Wireless Communications

http://www.nicepedia.com/wp-content/uploads/2011/07/The-History-of-Wireless-Communications.png Communications, various telecommunications systems that use radio waves to carry signals and messages across distances. Wireless communications systems include cellular telephones, pagers, radio telegraphs, satellite telephones, laptop computers, personal digital assistants (PDAs), shortwave radios, and two-way radios. They are used primarily to transmit private communications. Commercial radio and television are also wireless telecommunications systems, but radio and television are mainly public broadcast services rather than private communications systems (see Radio and Television Broadcasting). This article focuses on wireless communications systems that are used primarily for private communications.

Wireless communications allow people greater flexibility while communicating, because they do not need to remain at a fixed location, such as a home or office, but instead can communicate with other people while traveling in a car or walking along a street. Wireless technologies make communications services more readily available than traditional wire-based services (such as ordinary telephones), which require the installation of wires in fixed locations. Wireless communications devices are useful in places where communications services are only temporarily needed, such as at outdoor festivals or large sporting events. These technologies are also useful for communicating in remote locations, such as mountains, jungles, or deserts, where wire-based telephone service might not exist. Police, fire, and other emergency departments use wireless devices, such as two-way radio, to communicate information between vehicles that are already responding to emergency calls. Construction and utility workers frequently use handheld radios for short-range communication and coordination. Many businesspeople use wireless devices, such as cellular radio telephones, also known as cell phones, to stay in contact with colleagues and clients while traveling. Increasingly, people are using wireless devices for a variety of everyday purposes, such as scheduling appointments, arranging meeting places, shopping for food, or agreeing on home video selections while in a video store.

All wireless communications devices use radio waves to transmit and receive signals. These devices operate on different radio frequencies so that signals from one device will not overlap and interfere with nearby transmissions from other devices. The number of companies offering wireless communications services has grown steadily in recent years. For example, in 1988 about 500 companies offered cell phone services. By 2001 that number had grown to more than 2,500 companies serving about 120 million subscribers. Currently, telecommunications companies throughout the world are activating more wireless service subscriptions than they are conventional wire-based service subscriptions. Wireless communication is becoming increasingly popular because of the convenience and mobility it affords; the expanded availability of radio frequencies for transmitting, which makes it possible to handle a larger volume of calls; and improvements in technology, which have added other services such as Internet access and improved the clarity of voice transmissions.

The idea of wireless radio communications arose in the mid-1800s from the theories of two English physicists, Michael Faraday and James Clerk Maxwell. In 1888 German physicist Heinrich Hertz applied these theories to construct a spark-gap transmitter, a device that generated radio waves from an electric spark. In 1895 Italian electrical engineer Guglielmo Marconi extended the range of such transmissions and adapted the technology to send and receive wireless telegraph signals. In 1901 Marconi built the first transoceanic telegraph transmitter, which had a 3,400 km (2,100 mi) link from Poldhu, Cornwall, England, to St. John’s, Newfoundland.

Developments in vacuum tube technology in the early 1900s by English physicist and engineer Sir John Ambrose Fleming and American inventor Lee De Forest made it possible to modulate and amplify wireless signals to send voice transmissions. The range and clarity of voice transmissions increased as advancements in technology were made, and in 1915 the American Telephone & Telegraph Company transmitted a voice message by radio between the United States and France. By the 1930s small two-way radio transmitters were in common use among law enforcement and civil emergency authorities. Improvements in technology have made two-way communications systems smaller and lighter, with extended range and capabilities. See also Radio: History; Telecommunications: History; Telegraph.

References: http://www.nicepedia.com/information-technology/the-history-of-wireless-communications/