MOTOGRAPH

Mo"to*graph, n. [L. movere, motum, to move + -graph.] (Elec.)

Definition: A device utilized in the making of a loud-speaking telephone, depending on the fact that the friction between a metallic point and a moving cylinder of moistened chalk, or a moving slip of paper, on which it rests is diminished by the passage of a current between the point and the moving surface. -- Mo`to*graph"ic (#), a.

Source: Webster’s Unabridged Dictionary 1913 Edition