Information communication technology

Videoconferencing – The first concepts of video conferencing were developed in the 1870s, as part of an extension of audio devices. Today video conferencing is used by many industries, including educators, marketers.

6. 
   Cell phone/Mobile phone – - A mobile phone is frequently called a cellular phone or cell phone. Most mobile phones provide voice communication, short message service(SMS), Multimedia message service(MMS), and newer phones may also provide internet service such as web browsing, instant messaging capabilities and e-mail. The first handheld mobile phone was demonstrated by john F.Mitchell and martin cooper of Motorola in 1973, using a handset weighing c.2 kilograms.
   
7. 
   Radio
   
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   Telegraph
   

5. 
   Radio communication -
   

Radio waves were first identified and studied by German physicist Heinrich hertz in 1886. The early is the history of technology that produces and uses radio instruments that use radio wave. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". In radio communication system, information is carried across space using radio wave. At the sending end, the information to be sent is converted by some type of transducer to a time-varying electrical signal called the modulation signal. The modulation signal is applied to a radio transmitter.

6. 
   Microwave Communication -
   

Microwave technology was develop during world war II(1939-45) in connection with secret military radar research. Today , microwave are used parimarily in microwave ovens and communications. Microwave wireless communication is a very effective type of communication. Radio waves are used in this transmission. In this Communication, two methods are used to transfer data and information. One is satellite method and other is terrestrial method. Terrestrial refers to things related to land or the planet earth. Microwave refer to high frequencies above 300MHz and short wave lengths, at the microwave components depends on the changing electromagnetic fields instead of current in the conductor or voltage across the 2 points a microwave propagated through the line of sight, it is necessary to install repeater station at about 50km interval.