The telephone was discovered almost by accident. What people thought they were looking for was a way to make the telegraph work faster and more profitably - by sending distinct musical notes or tones simultaneously along the wires with a separate message sent on each frequency.
But they soon realised it could also include the human voice - a speaking telegraph. And if you could talk down a wire, wouldn't that be an entirely new and better way of communicating?
The individual parts of the telephone were discovered and developed by different people at different times.
Someone needed to take all those connections and draw them together into one working instrument. In the end that someone was Alexander Graham Bell - but he only just won the race.
Who really invented the telephone? There are quite a few candidates, and the leading one is a German science teacher called Philipp Reis.
Reis began work on the telephone in 1860, inspired by an 1854 paper by a French investigator named Bourseul, who suggested:
'Speak against one diaphragm and let each vibration 'make or break' the electric contact. The electric pulsations thereby produced will set the other diaphragm working, and [it then reproduces] the transmitted sound.'
His idea was a little shaky. To send sound, the transmitter diaphragm shouldn't completely make or break an electrical contact but instead should vary the current of electricity flowing. His transmitter was a make-and-break device but Reis's receiver (earpiece) used a vibrating rod (a knitting needle in fact) that was magnetised to varying degrees by an electric coil.
Reis was let down by his apparatus - it could reproduce continuous musical notes well but produced indistinct speech. His telephone was shown in demonstrations all over Europe, including one in Scotland while Alexander Graham Bell was there, visiting his father.
Timing is everything. Elisha Gray knew that all too well. On February 14, 1876, the day that Alexander Graham Bell applied for a patent for his version of the telephone, Elisha Gray applied for a caveat - a document indicating that he intended to file his own patent claim within three months.
But Gray was a few hours too late - Bell had already filed an actual patent application - and the courts later ruled that this took precedence.
Even so, Gray's claim has its merits - Bell first transmitted the sound of a human voice over a wire, using a liquid transmitter of the microphone type previously developed by Gray and unlike any described in Bell's previous patent applications. He also used an electromagnetic metal-diaphragm receiver of the kind built and used publicly by Gray several months earlier.
One summer afternoon, as Bell was working in his workshop in Boston, he heard an almost inaudible twanging sound from his prototype telephone - a sort of crude harmonica with a clock-spring reed, a magnet and a wire. This was connected to a similar device in another room where his assistant Thomas Watson was working.
Watson had snapped the reed on one of the instruments and from the other device Bell had heard exactly the same sound. It was the first time in the history of the world that a complex sound had been carried along a wire, and reproduced perfectly at the other end.
After hearing their telephone first transmit a sound in June 1875, Bell and Watson spent the next 40 weeks making their telephone actually speak. Finally, on March 10, 1876, Watson heard Bell's voice distinctly in the receiver saying: "Mr Watson, come here, I want you."
Watson, who was in another room, dropped the receiver and rushed with wild joy across the hall to tell the glad tidings to Bell. "I can hear you!" he shouted breathlessly. "I can hear the WORDS."
America's telegraph companies saw right away that Bell's telephone posed a powerful threat to their businesses and they tried to fight back. The Western Union company called on Thomas Alva Edison to develop an alternative to Bell's invention. The American Speaking Telephone Company in New York (a Western Union subsidiary) then went head-to-head with The Bell Telephone Company of Boston.
Within months, Bell sued Western Union for infringement of his patents. Western Union argued that it was Elisha Gray who had invented the telephone - but lost the court battle and had to hand over Edison's telephone rights and withdraw from the telephone business.
The Bell company absorbed the American Speaking Telephone Company and re-emerged as the American Bell Telephone Company in April 1880.
Sir William Thomson (later Lord Kelvin) exhibited Bell's primitive telephone before the British Association for the Advancement of Science assembly at Glasgow in September 1876, describing it as "the greatest by far of all the marvels of the electric telegraph".
The first pair of practical telephones seen in Great Britain arrived in July 1877, brought here by William Preece, Chief Electrician of the Post Office. A few months later, Bell's 'perfected' type of telephone was exhibited at another meeting of the British Association in Plymouth.
Within a year of making the first telephone call, Bell and his financial backers - Thomas Sanders and Gardiner G Hubbard - had formed the Bell Telephone Company in the United States.
Unsurprisingly, early demand for the telephone was not great and prior to forming their company Bell and his partners had struggled in their attempts to promote the new invention. At one point they even offered to sell the Bell patents to the Western Union Telegraph Company - Elisha Gray's employers - for $100,000. The offer was spurned - a decision the Western Union was soon to regret bitterly.
Alexander Graham Bell demonstrated his telephone to Queen Victoria on January 14, 1878, at Osborne House on the Isle of Wight. During the demonstration Bell made calls to London, Cowes and Southampton. These were the first publicly witnessed long-distance calls in the UK.
Less than six months after making his first British demonstrations, the UK rights to the Bell patents had been taken up by a new British company, The Telephone Company (Bell's Patents) Ltd. One of the first telephone lines to be erected was from London's Hay's Wharf, south of the Thames, to Hay's Wharf Office on the north bank.
