Radio signals must be modulated before being transmitted.
Tips
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Technical electronics term, common in Taiwan. Mainland engineering Chinese more often uses 调制 for the same concept (e.g. 调制解调器 = modem). Both come up in textbooks; 调制 is the safer mainland default.
mistakes
Read 调 as tiáo (2nd tone, 'to adjust'), not diào (4th tone, 'to transfer / tune'). Same character, different reading depending on meaning.
