In two phase systems flip-flops cutting the combinational circuit are used to latch the proper values. In order to understand two phase systems for latches, consider single latch shown in figure below. From figure it can be seen that, there is existence of relationship between the delays through the system and the clock signal. As long as the latch clock signal is high, the latch is transparent. The improved architecture of two-phase clocking system is shown in adjacent figure.
Fig_Two-Phase System