Credited to United States. Bell's patent was hotly contested, and Britannica treats the transmission of speech under the joint heading of Elisha Gray and Bell. Both worked in the United States, and the American Bell Telephone Co. litigation upheld Bell's patents.
How it began
Alexander Graham Bell, a teacher of the deaf from a family professionally involved with sound, speech and hearing, first worked on improving the telegraph. That research led him to consider whether speech itself could be sent electrically. On March 10, 1876, in his Boston laboratory, he spoke through his instrument to his assistant Thomas A. Watson in the next room: "Mr. Watson, come here, I want to see you." Bell recorded the experiment in his notebook that day and wrote to his father of "a great success."
Before it existed
In the mid-19th century the telegraph was the means of rapid long-distance communication, sending the dots and dashes of a code rather than speech. Its limits were soon reached, since only one message at a time could travel down a wire. Telegraph companies invested heavily in research to raise transmission rates, and inventors including Thomas Edison worked on machines that could send several messages at once.
How it works
Bell and Watson found that only a continuous current, rather than the interrupted pulses of the telegraph, could carry the varying waves of sound. Bell's early telephone used an electromagnet connecting two identical membranes. Sound waves from a voice made one membrane vibrate, producing a current with subtle fluctuations, and the membrane at the receiving end mimicked those vibrations and made them audible again.
What changed first
Bell showed the invention to the public at the world's fair in Philadelphia, where it won a prize, and press attention turned him from an unknown inventor into a public figure. On the day of the first call he predicted that wires would be laid on to houses "just like water and gas" and that friends would converse without leaving home. In 1892 he sat at the New York end of the first long-distance line to Chicago to inaugurate that service.
Where it stands today
Bell's experimental notebook entry of March 10, 1876, survives among nearly 150,000 items in the Alexander Graham Bell Family Papers at the Library of Congress, donated by his heirs in 1975 and partly published online. Britannica describes the telephone as a technology that remains an indispensable part of daily life.
