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In general, the radio is constructed by mechanical devices, electronic devices, magnets, etc. It receives audio signals emitted by broadcasting stations through converting electric wave signals.
After the invention of the vacuum tube, the circuit and receiving performance of the radio had undergone revolutionary progress and improvement, that is vacuum tube radio. Later, with the development of technology, radios with transistors as the core gradually became popular. It's what we know as a transistor radio.
Radios are still widely used for many functions. Here two main radios will be described in detail below.