A method for modifying the frequency of a clock signal includes the steps of producing a clock signal having voltage pulses which occur at a first frequency and producing a control signal having voltage pulses which occur at a lower frequency. The frequency of the voltage pulses in the control signal is incremented in successive time intervals and the clock signal and control signal are combined such that one voltage pulse in the clock signal is deleted for each voltage pulse in the control signal. This results in a modified clock signal having a frequency which may be ramped up or down depending upon the initial frequency of the control signal and the direction in which the frequency of the control signal is incremented.