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The History Of Radio, Radio And The Electromagnetic Spectrum, How Radio Signals Are Created, ModulationDemodulation

Radio is the technology and practice that enables the transmission and reception of information carried by long-wave electromagnetic radiation. Radio makes it possible to establish wireless two-way communication between individual pairs of transmitter and receiver, and it is used for one-way broadcasts to many receivers. Radio signals can carry speech, music, telemetry, or digitally-encoded entertainment. Radio is used by the general public, within legal guidelines, or it it is used by private business or governmental agencies. Cordless telephones are possible because they use low-power radio transmitters to connect without wires. Cellular telephones use a network of computer-controlled low power radio transmitters to enable users to place telephone calls away from phone lines.

Radio receivers recover modulation information in a process called demodulation or detection. The radio carrier is discarded after it is no longer needed. The radio carrier's cargo of information is converted to sound using a loudspeaker or headphones or processed as data.

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