Telephone Nameplates
The first significant advance in long-distance telephone service was the development of loading coils, an invention that reduced the propensity of a signal to deteriorate proportionately to the expanse of the transmission. In 1912, Dr. Lee DeForest developed the audion, which consisted of a three-element vacuum tube that could more effectively transmit and amplify radio waves. In 1913, Western Electric's Dr. Harold Arnold improved upon the audion with a high-vacuum tube that significantly amplified sound in telephone cables, prompting AT&T to acquire the audion patent from DeForest. The aforementioned technological developments result allowed Western Electric telephone to span the continent by 1914.
