A tone pulse generator is described, primarily intended for use as the stimulus source for Evoked Response Audiometry. The most interesting features are the electronic switch, using field-effect-transistors, and the triggering circuits with a random period mode incorporated. The triggering circuits can easily be adapted to trigger types of stimulus sources other than tone pulses, e.g. flashes, vibrotactile stimuli, current pulses etc., for different kinds of psychophysiological experiments.