Abstract: A materials handling or processing system which includes at least two processing devices such as shredders, for example, which are subject to unexpected and relatively sudden discontinuance of operation as by clogging or other breakdown condition, and transporting apparatus for conveying materials being processed to the processing devices, the invention comprising means for detecting such breakdown in one of the devices and for consequently directing to the second device the flow of materials normally directed to the broken down device, thereby maintaining continued processing of materials without interrupting their flow through the system.