Before the invention of the
electromagnetic telephone, there were mechanical acoustic devices for transmitting spoken words and music over a greater distance, faster than the speed of sound in air. The very earliest mechanical telephones were based on 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 extended wire. An acoustic string phone is attributed to him as early as 1667. For a short period, acoustic telephones were marketed commercially as
niche competitors to the electrical telephone, as they did not 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 and quickly went out of business. Their maximum range was very limited, but technical innovations (resulting in about 300 patents) increased their range to approximately , 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 rights-of-way, purportedly with a range of . In the centuries before tin cans and paper cups became commonplace, other cups were used and the devices were sometimes called "lovers' telephones". During the 20th century, they came into common use in preschools and elementary schools to teach children about sound vibration. == Operation ==