August 4, 1931 - The U.S. Patent Office finally approved Doolittle's 1921 patent application for "Sound-Recording and Sound-Reproducing and Locating Apparatus." He assigned his rights to Radio Corporation of America on June 14, 1921.

Doolittle was the founder of New Haven, Connecticut's radio station, WPAJ. It was renamed WDRC in 1925 and moved to Hartford in 1930.

Click here to read about Doolittle's other patents: 1921, 1924 & 1927.