Band timing generator

Abstract

This invention relates to a method and apparatus for reading periodic timing marks from a moving printing band and for generating synchronous timing marks during the passage of a missing timing mark on the printing band. Two timing mark sensors are positioned adjacent the printing band or belts but spaced from each other by a distance several multiples of the spacing between timing marks. The downstream or primary sensor is used to detect the passage of timing marks adjacent thereto. When the missing pulse passes the upstream or secondary detector, an electronic switch transfers the output line to the upstream sensor until the missing pulse passes the primary sensor. As the missing timing pulse passes the primary sensor, the switch is actuated to couple the output line again to the primary sensor. In this manner a continous stream of synchronized timing pulses will be generated by the sensors even during the period when the missing timing pulse passes adjacent the primary sensor.