What is "motograph"

Motograph \Mo"to*graph\, n. [L. movere, motum, to move + -graph.] (Elec.) 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. [obsolescent] -- Mo`to*graph"ic, a.