Abstract: A control apparatus for manufacturing or treatment processes in which articles or batches of articles are conveyed through a process station on endless conveyor means. The apparatus comprises electrical signal producing means for producing at its output an article or batch digital signal dependent upon the length of the conveyor means associated with one article or batch of articles. Electrical reference means capable of being set with a digital value representing the effective length of the conveyor means are provided together with electrical comparator means for receiving the signals at the outputs of said signal producing means and said reference means and for determining whether the effective length of the conveyor is an exact multiple of the length associated with the article or batch.