A plurality of two-input logic gates such as OR gates supplying their outputs to a three-input logic gate such as an AND gate and including a feedback connection from the three-input gate to all but one of the two-input gates. A control signal is applied to the two-input gate not receiving feedback and the complement of this control signal is applied to one of the other two-input gates. An information signal is applied to the two-input gate not receiving feedback and to a two-input gate not receiving the complement of the control signal.