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Telegraph
by Samuel Morse and Joseph Henry inter alia.
It was used as a method for sending messages; it started off with morse coding. -
Telephone
by Alexander Graham Bell.
It holds distant communication between 2 or more users. -
Radio
by Gugliemo Marconi (Nikola Tesla). It conveys info from one place to another through the intervening media without wires. -
TV
by Philo Farnsworth.
It's a telecommunication medium used for transmitting moving images in monochrome or in color, and in 2D or 3D and sound. -
Computer
by Alan Turing.
Its main usage is storing, retrieving and processing data. -
Tablet
by Alan Kay.
It is a mobile device in a single, thin and flat package. It's a computer with a tactile screen, and missing some input/output methods. -
Mobile phone
by Martin Cooper.
It is a small portable radio telephone. It can be used to communicate over long distances without wires.