On the morning of February 14, 1876, Bell and his representative filed for a patent at the Patent Office in Washington D.C. A few hours earlier that same day Elisha Gray had come to the same Patent Office and filed a document that amounted to the same thing. Bell’s claim was accepted first, quite likely out of order. Because of the sequence of activities that day the patent was awarded to Bell. It has been challenged often, but has withstood thousands of law suits.
The patent — No. 174,465 — was accepted on March 3, 1876, and issued on March 7. It was entitled "Improvements in Telegraphy", and did not so much as mention the word "telephone". It described 2 general methods of transmission: one by causing a membrane, attached to a nearby magnet, to vibrate. The magnet, mounted within a coil of wire, would move and induce a current in the wire. This was the so-called magneto-induction principle (an ill-fated approach that soon disappeared from the powering of telephone transmitters), and the second by causing speech to somehow vary the electrical resistance of a circuit. This method (described below) was vastly superior, and became the principal behind all non-electronic transmitters.
Most of Bell’s patent application pertained to the magneto-induction principal; the variable resistance principal was simply hand-written into the margin of the document. And, prior to the application, no experiments had been conducted regarding it.
It didn’t take long, however, for Bell and his assistant Thomas A. Watson, to remedy that. Back in their Boston shop at 5 Exeter Place the 2 succeeded in producing a working model of a telephone. The historic words "Mr. Watson — come here — I want you" would go down as the first spoken communications over an electrical circuit. The day was March 10, 1876. Notice that this was 1 week after the filing of the patent.
Just who was this man who is credited for inventing one of the most important devices in history? An engineer? A scientist? No, not at all. He was a man interested in "sounds" — primarily speaking and hearing. This came rather naturally, inasmuch as his grandfather was a Shakespearean actor, and his father, Melville Bell, was a distinguished teacher of elocution at the University of Edinburgh. Graham (as he liked to be called) taught music and elocution at a school near Edinburgh, and assisted his father by delivering lectures on what was called "visible speech" and by studying the anatomy of the vocal apparatus at University College, London.
In 1870 the Bell family moved to Brantford, Canada, a small industrial town some 30 miles north of the shore of Lake Erie and 60 miles west of Niagara Falls. Shortly after that Graham began work on a device that could be applied to the telegraphy business — he called it a "harmonic telegraph". The hope was that different tones could be transmitted down the telegraph wire, each of which would be keyed by the telegraph. At the distant end the tones would be separated. The goal, of course, was to be able to transmit several messages simultaneously on a single wire. Certainly such a device would have tremendous commercial applications — but such a goal was not enough for young Graham.
In addition to working on the magneto-induction principle (the approach used by most inventors of the day) he had learned that if the resistance of a wire could be varied the current in the wire would be varied. And if, at one end of a wire, a voice-activated device could be implemented that would vary the resistance of a current-carrying wire, at the other end of the wire a diaphragm could be vibrated by this varying current, so that sounds (or words) spoken into the transmitting end could be reproduced at the receiving end.
And this was the principal that allowed the spoken words to be transmitted electrically. Somehow put a device in an electrical circuit whose resistance would be varied by the spoken voice. At some distant point let the current in the wire "bias" a diaphragm. As the current in the wire varied, so also did the position of the diaphragm. And the result was sound.
Bell’s approach to varying the resistance of a wire was to dip one end of it into a conductive liquid. If the wire were dipped in deeply, then the overall resistance of the wire and the liquid would be lessened; if the wire were dipped in only a little, then the resistance of the wire/liquid combination would not be lessened.
But what liquid should he use? He tried water (no sound), cod liver oil (no sound), salt water (loud sound), liquor (loud sound), and a mixture of water and sulphuric acid. It was this last that worked best.
It was also the sulphuric acid that caused the situation that supposedly lead to the working model. Bell accidentally spilled a cup of acid over his clothes, and screamed (into the mouthpiece) "Mr. Watson – come here – I want to see you."
And so the telephone was born.
Or was it????
You will note that in the above we have said that Alexander Graham Bell was the first to patent the telephone. That does not mean that he was the first to invent the telephone. As we have seen, at least half a dozen people, from around the world, claimed to have invented the telephone (or major parts thereof) before Bell. Those most-mentioned are as follows:
Antonio Meucci. Meucci developed a device that employed a paired electro-magnetic transmitter and receiver, where the motion of a diaphragm modulated a signal in a coil by moving an electromagnet. The result was good fidelity, but a very weak signal. Meucci filed a caveat (the equivalent of a patent, but a document that required renewing on a periodic basis). Unfortunately, in 1874 (2 years before the Bell patent) he was on public aid, and was unable to renew the caveat, and by so doing (or failing to do so) he lost his rights to the "invention" of the telephone.
Charles Bourseul. Bourseul described, in 1854, a method of transmitting voice over wires (he was a telegraphist). However, he did not file for a patent
Johann Philipp Reis. 16 years before Bell’s patent application, Reis produced a device which could transmit musical notes, and even brief sentences. In 1863 the device was tested by Standard Telephones and Cables (STC), but because this company was currently bidding for a contract with Bell’s AT&T, the results were covered up by STC’s chairman to maintain Bell’s reputation.
Elisha Gray. Almost certainly Gray filed a caveat a few hours before Bell filed his patent application. The rather undisciplined operation of the patent office (and perhaps the unethical activities within it) resulted in the Bell patent being signed before the Gray caveat.
Once again we see that the invention of this major technological device was not the work of 1 man — rather it was the product of many. Each played a significant role.