Abstract: An apparatus for generating a signal having symmetrical waveform of frequency selectable according to a plurality of input signals. The frequency of the signal changes rapidly in response to changes in the input signals, and frequency changes occur in a coherent manner, with no perturbation of the output signal. A high speed clocking signal and the signals generated by its successive divisions are logically combined to produce a plurality of signals which are filtered to produce substantially symmetrical waveform signals which are maintained in periodic phase coherence. Under control of frequency select input signals, a selected one of the substantially symmetrical waveform signals is gated into a divider which provides a symmetrical waveform output signal having the selected frequency.