Abstract: A method and apparatus to correct a periodic signal, such as a frequency reference, based upon another frequency reference. A lower accuracy frequency signal generator (104) provides an uncorrected frequency reference signal (122) to a frequency corrector (106). Frequency corrector (106) counts cycles of a frequency reference signal (124), as generated by a higher accuracy reference generator (102) for a time period derived from the uncorrected frequency signal. Based upon the cycles counted, pulses are added or removed from the uncorrected frequency signal (122) to produce a corrected frequency signal (126). A ratio of pulses to be removed from the uncorrected frequency signal (122) is determined from the number of cycles counted and a counter arrangement is provided to automatically remove the required ratio of pulses from the uncorrected frequency signal (122).