Elisha Gray was a hard working professional inventor with some success to his credit. Born in 1835 in Barnesville, Ohio, Gray was well educated for his time, having worked his way through three years at Oberlin College. His first telegraph related patent came in 1868. An expert electrician, he co-founded Gray and Barton, makers of telegraph equipment. The Western Union Telegraph Company, then funded by the Vanderbilts and J.P. Morgan, bought a one-third interest in Gray and Barton in 1872. They then changed its name to the Western Electric Manufacturing Company, with Gray remaining an important person in the company. To Gray, transmitting speech was an interesting goal but not one of a lifetime.
Alexander Graham Bell, on the other hand, saw telephony as the driving force in his early life. He became consumed with inventing the telephone. Born in 1847 in Edinburgh, Scotland, Graham was raised in a family involved with music and the spoken word. His mother painted and played music. His father originated a system called visible speech that helped the deaf to speak. His grandfather was a lecturer and speech teacher. Bell's college courses included lectures on anatomy and physiology. His entire education and upbringing revolved around the mechanics of speech and sound. Many years after inventing the telephone Bell remarked, "I now realize that I should never have invented the telephone if I had been an electrician. What electrician would have been so foolish as to try any such thing? The advantage I had was that sound had been the study of my life -- the study of vibrations."
In 1870 Bell's father moved his family to Canada after losing two sons to tuberculosis. He hoped the Canadian climate would be healthier. In 1873 Bell became a vocal physiology professor at Boston College. He taught the deaf the visual speech system during the day and at night he worked on what he called a harmonic or musical telegraph. Sending several messages at once over a single wire would let a telegraph company increase their sending capacity without having to install more poles and lines. An inventor who made such a device would realize a great economy for the telegraph company and a fortune for his or her self. Familiar with acoustics, Bell thought he could send several telegraph messages at once by varying their musical pitch. Sound odd? I'll give you a crude example, a piano analogy, since Watson said Bell played the piano well.
Imagine playing Morse code on the piano, striking dots and dashes in middle C. Then imagine the instrument wired to a distant piano. Striking middle C in one piano might cause middle C to sound in the other. Now, by playing Morse code on the A or C keys at the same time you might get the distant piano to duplicate your playing, sending two messages at once. Perhaps. Bell didn't experiment with pianos, of course, but with differently pitched magnetic springs. And instead of just sending two messages at once, Bell hoped to send thirty or forty. The harmonic telegraph proved simple to think about, yet maddeningly difficult to build. He labored over this device throughout the year and well into the spring of 1874.
Then, at a friend's suggestion, he worked that summer on a teaching aid for the deaf, a gruesome device called the phonoautograph, made out of a dead man's ear. Speaking into the device caused the ear's membrane to vibrate and in turn move a lever. The lever then wrote a wavelike pattern of the speech on smoked glass. Ugh. Many say Bell was fascinated by how the tiny membrane caused the much heavier lever to work. It might be possible, he speculated, to make a membrane work in telephony, by using it to vary an electric current in intensity with the spoken word. Such a current could then replicate speech with another membrane. Bell had discovered the principle of the telephone, the theory of variable resistance, as depicted below. [Brooks] But learning to apply that principle correctly would take him another two years.
Bell continued harmonic telegraph work through the fall of 1874. He wasn't making much progress but his tinkering gathered attention. Gardiner Greene Hubbard, a prominent Boston lawyer and the president of the Clarke School for The Deaf, became interested in Bell's experiments. He and George Sanders, a prosperous Salem businessman, both sensed Bell might make the harmonic telegraph work. They also knew Bell the man, since Bell tutored Hubbard's daughter and he was helping Sander's deaf five year old son learn to speak.
In October, 1874, Green went to Washington D.C. to conduct a patent search. Finding no invention similar to Bell's proposed harmonic telegraph, Hubbard and Sanders began funding Bell. All three later signed a formal agreement in February, 1875, giving Bell financial backing in return for equal shares from any patents Bell developed. The trio got along but they would have their problems. Sanders would court bankruptcy by investing over $100,000 before any return came to him. Hubbard, on the other hand, discouraged Bell's romance with his daughter until the harmonic telegraph was invented. Bell, in turn, would risk his funding by working so hard on the telephone and by getting engaged to Mabel without Hubbard's permission.
In the spring of 1875, Bell's experimenting picked up quickly with the help of a talented young machinist named Thomas A. Watson. Bell feverishly pursued the harmonic telegraph his backers wanted and the telephone which was now his real interest. Seeking advice, Bell went to Washington D.C. On March 1, 1875, Bell met with Joseph Henry, the great scientist and inventor, then Secretary of the Smithsonian Institution. It was Henry, remember, who pioneered electromagnetism and helped Morse with the telegraph. Uninterested in Bell's telegraph work, Henry did say Bell's ideas on transmitting speech electrically represented "the germ of a great invention." He urged Bell to drop all other work and get on with developing the telephone. Bell said he feared he lacked the necessary electrical knowledge, to which the old man replied, "Get it!" [Grosvenor and Wesson] Bell quit pursuing the harmonic telegraph, at least in spirit, and began working full time on the telephone.
After lengthy experimenting in the spring of 1875, Bell told Watson "If I can get a mechanism which will make a current of electricity vary in its intensity as the air varies in density when a sound is passing through it, I can telegraph any sound, even the sound of speech." [Fagen] He communicated the same idea in a letter to Hubbard, who remained unimpressed and urged Bell to work harder on the telegraph. But having at last articulated the principle of variable resistance, Bell was getting much closer.
On June 2, 1875, Bell and Watson were testing the harmonic telegraph when Bell heard a sound come through the receiver. Instead of transmitting a pulse, which it had refused to do in any case, the telegraph passed on the sound of Watson plucking a tuned spring, one of many set at different pitches. How could that be? Their telegraph, like all others, turned current on and off. But in this instance, a contact screw was set too tightly, allowing current to run continuously, the essential element needed to transmit speech. Bell realized what happened and had Watson build a telephone the next day based on this discovery. The Gallows telephone, so called for its distinctive frame, substituted a diaphragm for the spring. Yet it didn't work. A few odd sounds were transmitted, yet nothing more. No speech. Disheartened, tired, and running out of funds, Bell's experimenting slowed through the remainder of 1875.
During the winter of 1875 and 1876 Bell continued experimenting while writing a telephone patent application. Although he hadn't developed a successful telephone, he felt he could describe how it could be done. With his ideas and methods protected he could then focus on making it work. Fortunately for Bell and many others, the Patent Office in 1870 dropped its requirement that a working model accompany a patent application. On February 14, 1876, Bell's patent application was filed by his attorney. It came only hours before Elisha Gray filed his Notice of Invention for a telephone.
Mystery still surrounds Bell's application and what happened that day. In particular, the key point to Bell's application, the principle of variable resistance, was scrawled in a margin, almost as an afterthought. Some think Bell was told of Gray's Notice then allowed to change his application. That was never proved, despite some 600 lawsuits that would eventually challenge the patent. Finally, on March 10, 1876, one week after his patent was allowed, in Boston, Massachusetts, at his lab at 5 Exeter Place, Bell succeeded in transmitting speech. He was not yet 30. Bell used a liquid transmitter, something he hadn't outlined in his patent or even tried before, but something that was described in Gray's Notice.
Bell's patent, U.S. Number 174,465, has been called the most valuable ever issued. If you have QuickTime or another way to view .tif files you can view the document at the United States Patent and Trademark site (external link). Search for it by the number. Each page of the six page document is about 230K. And yes, it is very hard to follow. Patents are meant to protect ideas, not necessarily to explain them . . .
The Watson-built telephone looked odd and acted strangely. Bellowing into the funnel caused a small disk or diaphragm at the bottom to move. This disk was, in turn, attached to a wire floating in an acid-filled metal cup. A wire attached to the cup in turn led to a distant receiver. As the wire moved up and down it changed the resistance within the liquid. This now varying current was then sent to the receiver, causing its membrane to vibrate and thereby produce sound. This telephone wasn't quite practical; it got speech across, but badly. Bell soon improved it by using an electromagnetic transmitter, a metal diaphragm and a permanent magnet. The telephone had been invented. Now it was time for it to evolve.
How the first telephone worked
Simplified diagram of Bell's liquid transmitter. The diaphragm vibrated with sound waves, causing a conducting rod to move up and down in a cup of acid water. Battery supplied power electrified the cup of acid. As the rod rose and fell it changed the circuit's resistance. This caused the line current to the receiver (not shown) to fluctuate, which in turn caused the membrane of the receiver to vibrate, producing sound.
This transmitter was quickly dropped in favor of voice powered or induced models. These transmitted speech on the weak electro-magnetic force that the transmitter and receiver's permanent magnets produced.
It was not until 1882, with the introduction of the Blake transmitter, that Bell telephones once again used line power. The so called local battery circuit used a battery supplied at the phone to power the line and take speech to the local switch. Voice powered phones did not go away completely, as some systems continued to be used for critical applications, those which may have been threatened by spark. In 1964 NASA used a voice powered system described as follows:
"A network of 24 channels with a total of more than 450 sound powered telephones, which derive their power solely from the human voice, provide the communications between the East Area central blockhouse (left) and the various test stands at NASA's George C. Marshall Space Flight Center here. . ." The complete article is here:
http://americanhistory.si.edu/scienceservice/007016.htm (external link)
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