Over Half-Century of Telephone Progress, 1920s: Short film explaining with stills the birth of the telephone, titles interspersed. Dramatizations of Dr. Bell’s first telephone call to Mr. Watson; of Dr. Bell demonstrating the device to Don Pedro of Brazil at the Centennial Exposition 1876 in Philadelphia; shots of operation of early switchboards. Shows operation of modern switchboard, closer shots of female operators. Shot of diagram describing a mechanical dialing system.