Alexander Graham Bell
Bell, with his assistant, devised a receiver, consisting of a stretched film or drum with a bit of magnetised iron attached to its middle, and free to vibrate in front of the pole of an electromagnet in circuit with the line. This apparatus was completed on June 2, 1875. On July 7, he instructed his assistant to make a second receiver which could be used with the first, and a few days later they were tried together, at each end of the line, which ran from a room in the inventor's house at Boston to the cellar underneath. Bell, in the room, held one instrument in his hands, while Watson in the cellar listened at the other. The inventor spoke into his instrument, "Do you understand what I say?" and Mr. Watson rushed back into the upstairs and answered "Yes." The first successful two-way telephone call was not made until March 10, 1876 when Bell spoke into his device, "Mr. Watson, come here, I want to see you." and Watson answered back and came into the room to see Bell. The first long distance telephone call was made on August 10, 1876 by Bell from the family home in Brantford, Ontario to his assistant in Paris, Ontario, some 16 km (10 mi.) away.