Tin-can telephone

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A tin-can telephone is a type of acoustic (non-electrical) speech-transmitting device made up of two tin cans, paper cups or similarly shaped items attached to either end of a taut string or wire. It is a particular case of mechanical telephony, where sound (i.e., vibrations in the air) is converted into vibrations along a liquid or solid medium. These vibrations are transmitted through the medium (string) and then converted back to sound.

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