In the 1870's, two inventors Elisha Gray and Alexander Graham Bell both independently designed devices that could transmit speech electrically (the telephone).

Both men rushed their respective designs to the patent office within hours of each other, Alexander Graham Bell patented his telephone first. Elisha Gray and Alexander Graham Bell entered into a famous legal battle over the invention of the telephone, which Bell eventually won.

By 1874, Bell's initial work on the harmonic telegraph had entered a formative stage with progress it made both at his new Boston "laboratory" as well as at his family home in Canada a big success. While working that summer in Brantford, Bell experimented with a "phonautograph", a pen-like machine that could draw shapes of sound waves on smoked glass by tracing their vibrations. Bell thought it might be possible to generate undulating electrical currents that corresponded to sound waves. Bell also thought that multiple metal reeds tuned to different frequencies like a harp would be able to convert the undulating currents back into sound. But he had no working model to demonstrate the feasibility of these ideas.

In 1874, telegraph message traffic was rapidly expanding and in the words of Western Union President William Orton, had become "the nervous system of commerce". Orton had contracted with inventors Thomas Edison and Elisha Gray to find a way to send multiple telegraph messages on each telegraph line to avoid the great cost of constructing new lines. When Bell mentioned to Gardiner Hubbard and Thomas Sanders that he was working on a method of sending multiple tones on a telegraph wire using a multi-reed device, the two wealthy patrons began to financially support Bell's experiments. Patent matters would be handled by Hubbard's patent attorney, Anthony Pollok.

In March 1875, Bell and Pollok visited the famous scientist Joseph Henry, who was then director of the Smithsonian Institution, and asked Henry's advice on the electrical multi-reed apparatus that Bell hoped would transmit the human voice by telegraph. Henry replied that Bell had "the germ of a great invention". When Bell said that he did not have the necessary knowledge, Henry replied, "Get it!" That declaration greatly encouraged Bell to keep trying, even though he did not have the equipment needed to continue his experiments, nor the ability to create a working model of his ideas. However, a chance meeting in 1874 between Bell and Thomas A. Watson, an experienced electrical designer and mechanic at the electrical machine shop of Charles Williams, changed all that.

With financial support from Sanders and Hubbard, Bell was able to hire Thomas Watson as his assistant and the two of them experimented with acoustic telegraphy. On June 2, 1875, Watson accidentally plucked one of the reeds and Bell, at the receiving end of the wire, heard the overtones of the reed; overtones that would be necessary for transmitting speech. That demonstrated to Bell that only one reed or armature was necessary, not multiple reeds. This led to the "gallows" sound-powered telephone, which was able to transmit indistinct, voice-like sounds, but not clear speech.

In 1875, Bell developed an acoustic telegraph and drew up a patent application for it. Since he had agreed to share U.S. profits with his investors Gardiner Hubbard and Thomas Sanders, Bell requested that an associate in Ontario, George Brown, attempt to patent it in Britain, instructing his lawyers to apply for a patent in the U.S. only after they received word from Britain.

Meanwhile, Elisha Gray was also experimenting with acoustic telegraphy and thought of a way to transmit speech using a water transmitter. On February 14, 1876, Gray filed a caveat with the U.S. Patent Office for a telephone design that used a water transmitter. That same morning, Bell's lawyer filed Bell's application with the patent office. There is considerable debate about who arrived first and Gray later challenged the primacy of Bell's patent. Bell was in Boston on February 14, 1876.

Bell's patent 174,465, was issued to Bell on March 7, 1876, by the U.S. Patent Office. Bell's patent covered "the method of, and apparatus for, transmitting vocal or other sounds telegraphically ... by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound". Bell returned to Boston the same day and the next day resumed work, drawing in his notebook a diagram similar to that in Gray's patent caveat.

On March 10, 1876, three days after his patent was issued, Bell succeeded in getting his telephone to work, using a liquid transmitter similar to Gray's design. Vibration of the diaphragm caused a needle to vibrate in the water, varying the electrical resistance in the circuit. When Bell spoke the famous sentence "Mr Watson—Come here—I want to see you" into the liquid transmitter, Watson, listening at the receiving end in an adjoining room, heard the words clearly. The world's first ever communication via the telephone.

The world changed forever on that day. First broadcast 2nd January, 1977

An Irish radio documentary from RTÉ Radio 1, Ireland - Documentary on One - the home of Irish radio documentaries