| Title |
Primary Class |
Description |
Inventor |
Assignee |
Issue Date |
Patent No. |
| Sound Telegraph |
-- |
"The employment of a sound conductor, which is also an electrical conductor, as a means of communication by sound between distant points." (There are not mentioned any devices for converting sound to electrical waves and electrical waves to sound. There is no mention of coils of wire or any magnetic device. Neither is there any mention of a battery or other source of electrical power, nor of a diaphragm.) |
Antonio Meucci |
___ |
December 12, 1871 |
Caveat #3335 |
| Improvement of Transmitters and Receivers for Electric Telegraphs |
178/17B |
Multiplexing intermittent signals on a single wire using multiple vibrating steel reeds in make-break circuits. Bell further developed this invention for the transmission of also undulatory signals as described in his famous patent (No. 174465) of March 7, 1876. |
Alexander Graham Bell |
Alexander Graham Bell; Thomas Sanders; Gardiner G. Hubbard |
April 6, 1875 |
US161739 |
| Improvement in electric telegraphs for transmitting musical tones |
178/47 |
The harmonic telegraph. Consisted of multi-tone transmitters, each tone being controlled by a separate telegraph key. Each electromagnet had a different electrical resistance and exerted a different magnetic pull on its armature and thus caused each armature to vibrate at a different frequency. Could transmit musical tones, but not intelligible speech. |
Elisha Gray; |
Samuel S. White |
July 27, 1875 |
US166096 |
| Improvement in telegraphy |
379/167.01 |
First telephone patent granted. "The method of producing variable electrical current in a circuit by varying the resistance in the circuit....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." (Application date: February 14, 1876, the same day, but a few hours before Gray's caveat.) |
Alexander Graham Bell |
___ |
March 7, 1876 |
US174465 |
| Instruments for transmitting and receiving vocal sounds telegraphically |
-- |
The water transmitter described in Gray's caveat was strikingly similar to the experimental telephone transmitter tested by Bell on March 10, 1876, a fact which raised questions about whether Bell (who knew of Gray) was inspired by Gray's design or vice versa. A metal rod vibrating up and down in acidulated water would alternately lengthen and shorten the small distance between the bottom end of the rod and a metal plate at the bottom of the glass container holding the water, thus changing the electrical circuit resistance. (See Bell's patent No. 174465, above.) |
Elisha Gray |
___ |
February 14, 1876 |
Caveat |
| Electric Telegraphy |
379/167.01 |
An electromagnetic (magneto) telephone using permanent magnets, iron diaphragms, and a call bell. |
Alexander Graham Bell |
___ |
January 30, 1877 |
US186787 |
| Improvement in carbon telephones |
381/180 |
Consisting of two metal plates separated by granules of carbon. One plate faces outward and acts as a diaphragm. When sound waves strike this plate, the pressure on the granules changes, which in turn changes the electrical resistance between the plates. Edison's carbon granules transmitter was used with improvements by the Bell system for many decades thereafter. |
Thomas Alva Edison |
Western Union Telegraph Company |
December 9, 1879 |
US222390 |
| Improvement in Electrical Contact-Telephone |
381/178 |
Carbon diaphragm microphone. The invention of the carbon microphone (then called a "transmitter") was claimed both by Thomas Alva Edison in March 1877 and separately by Emile Berliner who filed related patent applications in June 1877 and August 1879. The two sides fought a long legal battle over the patent rights. Ultimately a federal court awarded Edison full rights to the invention of the carbon microphone, saying "Edison preceded Berliner in the transmission of speech...The use of carbon in a transmitter is, beyond controversy, the invention of Edison" and the Berliner patent was ruled invalid. British courts also ruled in favor of Edison over Berliner (See patent No.222390). |
Emile Berliner |
___ |
December 16, 1879 |
US222652 |
| Photophone Transmitter |
398/133 |
The device allowed for the transmission of sound on a beam of light. Bell believed the photophone was his most important invention."the greatest invention [I have] ever made, greater than the telephone". The idea of the photophone was thus to modulate a light beam: the resulting varying illumination of the receiver would induce a corresponding varying resistance in selenium cells, which were then used by a telephone to regenerate the sounds captured at the receiver. Crystalline selenium electrical resistance varies inversely with the illumination falling upon it, i.e., its resistance is higher when it is in the dark, and lower when it is exposed to light. |
Alexander Graham Bell; Sumner Tainter |
___ |
December 14, 1880 |
US235496 |
| Multiple Switch Board for Telephone Exchanges |
379/313 |
The first telephone switchboard |
Leroy B. Firman |
Western Electric Manufacturing Company |
January 17, 1882 |
US252576 |
| Automatic Telephone Exchange |
379/302 |
The early Strowger selector stepping switch |
Almon Brown Strowger |
___ |
March 10, 1891 |
US447918 |
| Telephone |
381/180 |
Carbon transmitter. This design was used until 1925. |
Anthony C. White |
American Bell Telephone Company |
November 1, 1892 |
US485311 |
| Electrical Exchange |
379/194 |
First commercial Strowger telephone exchange. |
Alexander E. Keith; Frank A. Lundquist; John Erickson; Charles J. Erickson |
Strowger Automatic Telephone Exchange |
May 28, 1895 |
US540168 |
| Calling Device for Telephone Exchanges |
379/365 |
The early form of the rotary dial; based on a finger wheel dial. |
Alexander E. Keith; John Erickson; Charles J. Erickson |
Strowger Automatic Telephone Exchange |
January 11, 1898 |
US597062 |
| Wireless Telephone |
178/43 |
The diagram shows wireless telephony from trains, boats, and wagons. In foreign patents he shows wireless telephony with cars. However, there is no indication that he was using voice-modulated continuous high frequency waves, as used for radio today. |
Nathan B. Stubblefield |
Conn Linn; R. Downs; B. F. Schroader; George C. McLarin; John P. McElrath; Jeff D. Roulette; Samuel B. Bynum |
May 12, 1908 |
US887357 |
| Line Switch |
335/112 |
Crossbar Line Switch |
John Newberry Reynolds |
Western Electric Company |
June 10, 1919 |
US1306124 |
