Abstract: From a first aspect this invention provides a missing pulse detector for determining the true termination time of a sequence of pulses in a signal of an assumed predetermined length having a rising edge and a trailing edge which may include pulses which do not reach a predetermined threshold, the detector including a counter connected to count pulses exceeding said threshold, up to a predetermined number, an oscillator for producing pulses at twice the frequency of the pulses in the signal and an enabling circuit for allowing pulses from the oscillator to pass to the counter only after the termination of a sequence of threshold-exceeding pulses from the signal.