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   Telephone

   11 February 1876 — Gray invents a liquid transmitter for use with a telephone but does not build one. ... 7 March 1876 — Bell's U.S. patent 174,465 "Improvement in Telegraphy" is granted, covering "the method of, and 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."
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   Timeline of the telephone

   May 1874: Gray invents electromagnet device for transmitting musical tones. ... 20 March 1880: National Bell Telephone merges with others to form the American Bell Telephone Company.
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   Johann Philipp Reis

   Johann Philipp Reis (January 7, 1834 – January 14, 1874) was a self-taught German scientist and inventor, who in 1860-1861 constructed an early telephone, today called the Reis telephone. ... If Reis' phone was adjusted so the contact points made a "loose metallic contact", they would function much like the later telephone invented by Berliner or the Hughes microphone, one form of which had iron nails in loose contact.
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   Nathan Stubblefield

   The photophone allowed for the transmission of both sound and articulate speech on a beam of light, and on June 3, 1880 Bell and Tainter transmitted the world's first wireless telephone message on their newly invented form of telecommunication. ... Lochte, Bob, Kentucky Farmer Invents Wireless Telephone!
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   Secure telephone

   A secure telephone is a telephone that provides voice security in the form of end-to-end encryption for the telephone call, and in some cases also the mutual authentication of the call parties, protecting them against a man-in-the-middle attack. Concerns about massive growth of telephone tapping incidents lead to growing demand for secure telephones.
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   Cordless telephone

   A cordless telephone or portable telephone is a telephone with a wireless handset that communicates via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station (which has the handset cradle). ... Advanced models began to use voice inversion as a basic form of scrambling to help limit unauthorized eavesdropping.
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   Telephone exchange

   In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls. ... The most common form of this used a steady 2,600 Hz tone to identify a trunk as idle.
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   Invention of the telephone

   The modern telephone is the culmination of work done by many individuals, all worthy of recognition for their contributions to the field. ... This form was patented January 30, 1877.
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   Timeline of hindu history

   -750: Priestly Sanskrit is gradually refined over next 500 years, taking on its classical form. ... 1876: Alexander Graham Bell invents the telephone.
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    New England Telephone and Telegraph Company

    The New England Telephone and Telegraph Company was a very early company set up to develop the then-new telephone. ... The National Bell Telephone Company merged with others on March 20, 1880 to form the American Bell Telephone Company.

Explore the following pages on Powerset:

• Telephone,
• Timeline of the telephone,
• Johann Philipp Reis,
• Nathan Stubblefield,
• Secure telephone,
• Cordless telephone,
• Telephone exchange,
• Invention of the telephone,
• Timeline of hindu history,
• New England Telephone and Telegraph Company

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