Tin can telephone

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 form of mechanical telephony, where sound is converted into and then conveyed by vibrations along a liquid or solid medium, and then reconverted back to sound.

Before the invention of the electromagnetic telephone, there were mechanical acoustic devices for transmitting spoken words and music over a distance greater than that of normal speech. The very earliest mechanical telephones were based on sound transmission through pipes or other physical media, and among the very earliest experiments were those conducted by the British physicist and polymath Robert Hooke from 1664 to 1685. From 1664 to 1665 Hooke experimented with sound transmission through a taut distended wire. An acoustic string phone is attributed to him as early as 1667.

The highly similar acoustic tin can telephone, or 'lover's phone', has also been known for centuries. It connects two diaphragms with a taut string or wire, which transmits sound by mechanical vibrations from one to the other along the wire (and not by a modulated electric current). The classic example is the children's toy made by connecting the bottoms of two paper cups, metal cans, or plastic bottles with tautly held string.

For a short period of time acoustic telephones were marketed commercially as a niche competitor to the electrical telephone, as they preceded the latter's invention and didn't fall within the scope of its patent protection. When Alexander Graham Bell's telephone patent expired and dozens of new phone companies flooded the marketplace, acoustic telephone manufacturers could not compete commercially and quickly went out of business. Their maximum range was very limited, but hundreds of technical innovations (resulting in about 300 patents) increased their range to approximately a half mile (800 m) or more under ideal conditions. An example of one such company was Lemuel Mellett’s 'Pulsion Telephone Supply Company' of Massachusetts, which designed its version in 1888 and deployed it on railroad right-of-ways, purportedly with a range of 3 miles (4.8 km).

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