The wireless technology was start in 1894 when an Italian physicist Guglielmo Marconi found a method of transmitting electromagnetic signals through the air. In 1912, Edwin Armstrong improved the Audion. He discovered that feeding the signal back the tube the power of the Audion could be increased. He continued experimentation resulted in the invention of Frequency modulation which is technology used in FM radio and other forms of wireless technology. In Frequency modulation one wave containing the information to be transmitted is combine with another wave, called a carrier wave, whose frequency is constant.In 1946 , Bell Laboratories connect the first wireless car phone to the St. Louis network. In 1962, Telstar Satellite successfully transmitted television and telephone conversation across the Atlantic for the first time.
Wired Communication refers to the transmission of data over a wire-based communication technology. Therefore communication devices cannot be connected if there is no wire to connect to another device. The early wired communication was used by Western Union Telegraph Company with the help of telegraph key to send Morse's famous telegraph message in 1856 . There are over two thousand telegraph offices operated across the United States. Wires criss-crossing cities and states and terminating in several exchanges(switching point) or central offices. Operators would connect the circuits and complete the call for the subscriber.In 1878, the first telephone exchange which connect 21 separated lines opened in New haven, Connecticut. In 1889 Almon Strowger developed the automatic switch called the step-by-step. In 1896 he replaced the button-pushing method with a rotary dialer. Then come to year 1913, N.J. Reynolds, a Western Electric engineer, developed a better automatic switch, the crossbar switch. It used a grid of horizontal and vertical bars, with electromagnets at their ends. The horizontal bars could rotate up and down ti connect to specific vertical bars and thus complete circuits. In the mid of 20 century AT & T integrated electronics into crossbar switches and in 1965, the first electronic switching system was used which can handled up to 65,000 two-way voice circuits. Until 1970 all telephone switches depended on a continuous physical connection to complete and maintain the call and new electronic switching device was put into service in 1976.
