a circuit arrangement for deriving a field synchronizing signal from an incoming signal which contains at least line synchronizing and field synchronizing pulses the amplitude of which extends between a reference and a peak level , comprising a signal generator for generating a signal each time a pulse having a value which is located between the reference and the peak level occurs in the incoming signal . said signal whose value is a measure of the duration of said pulse is compared with a first threshold value . during the occurrence of the line synchronizing pulses the signal of the signal generator is inhibited as long as the first threshold value has not yet been reached . the signal from the signal generator is compared with a second threshold value which is a measure of a pulse duration which exceeds the duration corresponding to the first threshold value . the field synchronizing signal is generated as soon as the second threshold value is reached .