Abstract: Apparatus for use as an ultrasonic pest repeller capable of having three different modes of operation for the purpose of generating ultrasonic signals for use in repelling all types of pests. The apparatus includes a circuit coupled at its output with one or more ultrasonic transducers and the circuit operates to generate electronic signals which are applied to the transducer or transducers for creating the ultrasonic signals in any one of three different modes of operation including a first mode in which a steady, modulated signal is generated, a second mode in which a dual pulse signal is generated with modulation of each pulse, and a third mode in which a signal is swept over a band of frequencies and is modulated simultaneously with the sweeping action. The circuit includes a rectifier for providing a DC regulated voltage.