Abstract: A transmission system comprising a plurality of stations, each having transmission and receiving circuits, that are connected in a ring configuration and use a HDLC-type protocol for transmission. The fault of a transmission circuit in a station can be detected in an idle state time by transmitting a fixed bit pattern during an idle state of transmission. Each station has a fixed bit pattern generator for outputting a fixed bit pattern during an idle time. Each station also has fault detection means which detects a fault when it receives a signal other than transmission data and the fixed bit pattern. Since the state of a line can always be monitored, a fault of the line state can be rapidly identified. Since transmission data is not encoded, the data transmission can be conducted at a high speed.

Abstract: A chopper-folder for restraining movement of a paper sheet relative to a folding slot as the sheet is conveyed along a path in a rotary printing press. The chopper-folder includes stoppers for stopping the movement of the paper sheet, restraining members for restraining vertical movement of the side edge portions of the paper sheet during the chopper-fold operation, and a driving unit for supporting and simultaneously driving the restraining members and the stoppers to conduct the chopper-fold operation. The stoppers, restraining members and the driving unit are mounted to the chopper-folder in such a manner that they can be easily moved away from the folding slot when jamming occurs during the chopper-fold operation, to facilitate quick and easy correction of the problem.