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Telegraph is a system for transmitting messages from a distance along a wire, especially one creating signals by making and breaking an electrical connection. -
Telephone is a system for transmitting voices over a distance using wire or radio, by converting acoustic vibrations to electrical signals. -
A computer is an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program. -
Radio is the transmission and reception of electromagnetic waves of radio frequency, especially those carrying sound messages. -
Television is a system for converting visual images (with sound) into electrical signals, transmitting them by radio or other means, and displaying them electronically on a screen. -
Mobile phone is a telephone with access to a cellular radio system so it can be used over a wide area, without a physical connection to a network. -
A tablet is a wireless, portable personal computer with a touchscreen interface. The tablet form factor is typically smaller than a notebook computer, but larger than a smartphone.