<Li> 1877: The first experimental Telephone Exchange in Boston . </Li> <Li> 20 January 1877: Edison "first (succeeds) in transmitting over wires many articulated sentences" using carbon granules as a pressure - sensitive varying resistance under the pressure of a diaphragm . </Li> <Li> 30 January 1877: Bell's U.S. Patent No. 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell . </Li> <Li> 4 March 1877: Emile Berliner invents a microphone based on "loose contact" between two metal electrodes, an improvement on Reis' Telephone, and in April 1877 files a caveat of an invention in process . </Li>

When was the telephone first used in homes