Amos Dolbear

Amos Dolbear
Amos Dolbear, ca. 1880
Born	(1837-11-10)November 10, 1837 Norwich, Connecticut
Died	February 23, 1910(1910-02-23) (aged 72)

Amos Emerson Dolbear (November 10, 1837 – February 23, 1910) was an American physicist and inventor. Dolbear researched electrical spark conversion into sound waves and electrical impulses. He was a professor at University of Kentucky in Lexington from 1868 until 1874. In 1874 he became the chair of the physics department at Tufts University in Medford, Massachusetts. In 1899 one of his patents was purchased in an unsuccessful attempt to interfere with Guglielmo Marconi's activities in the United States.

Dolbear was a graduate of Ohio Wesleyan University, in Delaware, Ohio. While a student at Ohio Wesleyan, he had made a "talking telegraph" and invented a receiver containing two features of the modern telephone: a permanent magnet and a metallic diaphragm that he made from a tintype. He invented the first telephone receiver with a permanent magnet in 1865, 11 years before Alexander Graham Bell patented his model. Later, Dolbear couldn't prove his claim, so Bell kept the patent. Dolbear lost his case before the U. S. Supreme Court, (Dolbear et al. v. American Bell Telephone Company). The June 18, 1881 edition of Scientific American reported:

In 1876, Dolbear patented a magneto electric telephone. He patented a static telephone in 1879.

In 1882, Dolbear was able to communicate over a distance of a quarter of a mile without wires in the Earth. His device relied on conduction in the ground, which was different from later radio transmissions that used electromagnetic radiation. He received a U.S. patent for a wireless telegraph in March of that year. His set-up used phones grounded by metal rods poked into the earth. His transmission range was at least as much as a half a mile and he received a patent for this device, U.S. Patent 350,299, in 1886. (He did not patent his system in Europe.)