From telegraph to telephone¶
By the 1870s the electric telegraph had spread across continents and under oceans. It could only send on/off pulses, though, and one wire carried one message at a time. Telegraph companies wanted more traffic over each wire. Several inventors worked on the harmonic telegraph, which sent several Morse messages at once, each on its own audio frequency.
Alexander Graham Bell and Elisha Gray were both working on that problem. Bell was a teacher of the deaf and knew a great deal about acoustics and speech. Both men realized the same idea could go further: if a wire could carry several tones, it could carry the complex, continuously varying waveform of a human voice.
The patent race¶
- February 14, 1876: Bell's lawyer filed his patent application at the U.S. Patent Office. The same day, Gray filed a caveat, a notice that he intended to patent a similar device. Historians have argued for well over a century about which arrived first and whether information passed between the filings.
- March 7, 1876: Bell was granted U.S. Patent 174,465 for "Improvements in Telegraphy." It is often called one of the most valuable patents ever issued.
- March 10, 1876: Bell spoke to his assistant Thomas Watson in another room, "Mr. Watson, come here," and was heard over the wire. That was the first intelligible telephone transmission.
Antonio Meucci, an Italian immigrant in New York, had built voice-transmission devices years earlier and filed a caveat in 1871. He could not afford to renew it. In 2002 the U.S. House of Representatives passed a resolution recognizing his contributions. The question of who invented the telephone has no single clean answer: several people were converging on the same idea at the same time.
Ontario's role¶
Bell's family had emigrated from Scotland to Brantford, Ontario, in 1870. Bell later said the telephone was conceived at the family homestead in 1874. In August 1876 he made the first long-distance call: about 13 km from Brantford to Paris, Ontario, over telegraph wires. Brantford still calls itself "the Telephone City." The Bell Homestead is a National Historic Site.
How the first telephones worked¶
Early telephones used electromagnetic transmitters. The voice vibrated a thin iron diaphragm near a magnet wrapped in a coil, which induced a small current. The same device worked as a receiver in reverse. These signals were very weak, so early phones only worked over short distances, and users often had to shout. Fixing that came next (see Building the early network).