Abstract: A circuit for generating at least two periodic output signals having a phase relationship controllable between zero and 180 degrees as a function of a d.c. control signal as compared to a ramp signal. Also included is circuitry for controlling the phase relationship to be at substantially 180 degrees when the d.c. control signal is always greater than the ramp signal and to be at substantially zero degrees when the d.c. control signal is always less than the ramp signal.

Abstract: An apparatus for generating a selected one of a plurality of ringing frequencies utilizing a single frequency source. A first counting means is utilized to divide the source frequency by a first predetermined integer to generate a series of address signals at a rate proportional to the selected ringing frequency. A read only memory is responsive to the address signals for generating a series of values representing points along a sine wave form such that, as the first counting means continuously cycles to a maximum count total equal to the number of values stored in the read only memory, the sine wave form is repetitively generated. If the source frequency is not an integer multiple of the selected frequency, the first integer is selected to generate the closest higher frequency and a second counting means is utilized to increase the time required for the first counting means to generate all of the address signals for one cycle of the sine wave form.