Thomas Edison invents and develops the carbon…

Thomas Edison invents and develops the carbon microphone that will be used in all telephones, along with the Bell receiver, until the 1980s.

The invention of the carbon microphone (at this time called a "transmitter") is claimed both Edison in March 1877 and separately by Emile Berliner who files a related patent application in June 1877. (Berliner will file another in August 1879. After protracted patent litigation, in 1892 a federal court will rule that Edison and not Berliner was the inventor of the carbon microphone.).

The carbon microphone will also be used used in radio broadcasting and public address work through the 1920s.

Edison begins work on an electric lamp in 1878, seeking a material that could be electrically heated to incandescence in a vacuum.

He applies the term filament to the element of glowing wire carrying the current, although the English inventor Joseph Swan had used the term prior to this.