This paper describes the generation of various waveforms with bulk semiconductor (Gunn-effect) oscillators having non-uniform cross sections or connected to external resistive circuits by means of small contacts attached to the bulk between the cathode and anode. In nonuniform oscillators, if the variation of the cross section is gradual, a high-field domain is equivalent to a constant current density generator moving at constant velocity. From this simple model, oscillating current waveforms are closely related to the cross-sectional area of the device. The oscillating frequency can be tuned or switched by the bias voltage. In multiterminal oscillators, the cathode current changes whenever a domain passes one of the small contacts connected to the external circuit. The waveforms can be controlled by changing the external circuit parameters. The characteristics of these devices operating in the frequency range from 50 to 150 MHz were extensively studied by changing both the device configuration and the external resistances.