Abstract: A ribbon lift-up apparatus for selectively rotating a ribbon cartridge holder to the printing position or the correcting position uses a disc cam provided with various cam grooves for the printing operation and correcting operation, respectively. The disc cam includes a circular first cam groove for continuous printing operation. The first cam groove has a specified radius with the rotation axis of the disc cam as a center thereof. A second cam groove for single type printing operation is provided and a cam follower pin is positioned initially at a home position in this second cam groove. The second cam groove is in communication with the first cam groove. A third cam groove for a correcting operation is also provided. The follower pin will initially be at the home position of the second cam groove and will cross the first cam groove during the correcting operation. The third cam groove has a smaller radius than the specified radius of the first cam groove.

Abstract: In an electrostatic reproduction machine there is provided one or more rollers capable of rotating in union with a copy sheet being advanced, in the course of travel of the copy sheet. Sensing switches are provided for sensing nonuniformity in rotation of the rollers which may occur in abnormal copy sheet transportation states and, more particularly, in a jam state. The outputs from the sensing switches are utilized for identifying the abnormal machine states.