apparatus for eliminating , in each clock distribution amplifier of a clock distribution system , sequential pulse catch - up error due to one pulse &# 34 ; overtaking &# 34 ; a prior clock pulse . the apparatus includes timing means to produce a periodic electromagnetic signal with a fundamental frequency having a fundamental frequency component v &# 39 ; 01 ; an array of n signal characteristic detector means , with detector means no . 1 receiving the timing means signal and producing a change - of - state signal v 1 in response to receipt of a signal above a predetermined threshold ; n substantially identical filter means , one filter means being operatively associated with each detector means , for receiving the change - of - state signal v n and producing a modified change - of - state signal v &# 39 ; n having a fundamental frequency component that is substantially proportional to v &# 39 ; 01 with a cumulative phase shift θ n having a time derivative that may be made uniformly and arbitrarily small ; and with the detector means n + 1 receiving a modified change - of - state signal v n from filter means no . n and , in response to receipt of such a signal above a predetermined threshold , producing a change - of - state signal v n + 1 .