Abstract: A continuous clear surfaced web adapted to be fed from a supply roll thereof for a converting operation thereon is preprinted with a succession of identical repeat patterns extending over the entire width of the web. Each pattern consists of areas which contain printed matter and at least one longitudinable discontinuous area or segment which, except for the presence of a printed register mark therein, is clear and unprinted. A photo sensitive scanner is directed at the register mark track of the feeding web for detecting the register marks and controlling in accordance therewith the timing of an associated machine operation, such as web splicing, so as to be performed in register with the web pattern. The operation of the scanner is controlled by a digital reset counter of pulses fed from a pulse generator driven by the web feeding mechanism. The counter is reset to zero upon the detection of each register mark.