Electro-motograph

An invention of Thomas A. Edison. A cylinder of chalk, moistened with solution of caustic soda, is mounted so as to be rotated by a handle. A diaphragm has an arm connected to its center. This arm is pre ed against the surface of the cylinder by a spring. When the cylinder is rotated, a constant tension is exerted on the diaphragm. If a current is pa ed through the junction of arm and cylinder the electrolytic action alters the friction so as to change the stre upon the diaphragm. human voice through a microphone the succe ive variations in strain upon the diaphragm will cause it to emit articulate sounds. These are produced directly by the movement of the cylinder, the electrolytic action being rather the regulating portion of the operation. Hence very loud speaking telephone. The same principle may be applied in other ways. But the practical application of the motograph is in the telephone described. IMG:8956969607833025625_229F158.jpg: Fig. 158. ELECTRO-MOTOGRAPH TELEPHONE