The present method is directed to techniques for estimating and periodically controlling the reactor split of alpha-olefin polymerizations using multiple catalysts that selectively incorporate monomers and other reactants into polymer compositions. Phase comparators receive frequency divided signals NHOLDH and NHOLDL generated from a data signal RDNRD, respectively, and intermittently perform a phase comparison between a signal dDAT and a signal CLK. The light-emitting device is positioned for generating light to be directed toward the catcher’s fingers to increase the visibility of hand signals given by the catcher.