Abstract: A field blanking pulse modifier in which the line synchronizing pulses and the field blanking pulse of a conventional television signal are derived. A counter is arranged to be reset by the field blanking pulse and to count the detected line synchronizing pulses or multiples thereof. An offset count is set corresponding to half the desired difference in duration between the modified field blanking pulse to be generated and the field blanking pulse of the television signal. The generation of the modified field blanking pulse is initiated when the sum of the counter content and the offset count is equal to the counter content which results after the counting of all the line synchronizing pulses between two successive field blanking pulses of the television signal, and the generation of the modified field blanking pulse is terminated when the counter content is equal to the offset count.