A digitally controllable oscillator is provided with a variable-frequency ring oscillator including an odd number of inverting circuits connected together in a ring formation. The oscillator has a pulse circulation device to circulate a pulse signal through the inverters to introduce some delay in the signal. Digital data is produced by a data controller device. A counter is connected to the pulse circulation device and counts the number of times the pulse signal circulates through the inverters. A pulse is generated at a desired frequency based upon the counter's output and the introduced delay. A control device determines which of a plurality of delay signals is applied to the circuit that generates the pulse at the desired frequency.