The telephone is a device for conducting spoken conversations across any distance beyond the range of the unaided human ear or the unamplified human voice. It works by transferring the atmospheric vibrations of human speech into a solid body, and by converting those vibrations into electrical impulses sent through a conducting medium—originally metal wires, but now optical fibers and electromagnetic microwaves as well. The word is a compound of two Greek words, " tele " ("far") and " phone " ("sound"), and the instrument is the most widely-used of all telecommunications appliances, with hundreds of millions of telephones in use all over the world. On any given business day, approximately two billion calls are placed, just in the United States. The telephone is also the archetypal electronic "medium," in the sense of the word intended by Marshall McLuhan—an "extension of man"—but its social impact is grossly understudied in favor...