PURPOSE: To manufacture a small-sized, accurate and unexpensive synchronizing pulse detector by using a dispersion type delay line for the separation of a synchronizing pulse.

CONSTITUTION: A high frequency pulse inputted to an input terminal 101 is applied to the dispersion type delay line 103 through an error detection preventing switch 102. A high frequency signal (a) inputted to the dispersion type delay line 103 and having pulse-modulated different frequency f1, f2 is delayed by T1, T2 and outputted, so that the frequency components f1, f2 are separated in accordance with time. A pulse analysing circuit 104 counts up pulse-like high frequency signals generated correspondingly to the frequency separated with time to decide a synchronizing pulse with two waves. The titled detector can be also applied to a device detecting synchronizing pulses having N different frequency.