PURPOSE: To obtain a decoder signal without producing an unnecessary pulse, by using a T type flip-flop constituting a synchronizing counter through inversion.

CONSTITUTION: An output of the T type flip-flops TF1, TF2 is inverted with inverters G20, G21, G22 and G23 to form the outputs of -Q1', Q', -Q2', Q2', and a decoded output is obtained by using them, where OUT1=Q'.Q2' and OUT2= -Q1'.-Q2' are obtained. No unnecessary pulse is given in the decoded outputs OUT1 and OUT2, because signals inverted at inverters G20∼G23 is decoded and a signal to be going to "H" goes to "H" after a signal to be going to "L" goes to "L" among the signals Q', -Q1', Q2', -Q2'.