Abstract: A voltage and frequency control circuit converts an alternating current input signal with inconstant frequency and voltage amplitude to an alternating current output signal with constant voltage amplitude and a constant nominal frequency which is lower than the lowest occurring frequency of the input signal. An amplitude control circuit converts the input signal to an ac signal having constant voltage amplitude. A rectifier circuit is regulated by an ac voltage source to provide positive half-cycles of the output signal from the amplitude control circuit during the positive half of the ac voltage source cycle and to provide negative half-cycles of the output signal during the negative half of the ac voltage source cycle. A filter circuit smooths and shapes the output of the rectifier circuit to provide a sinusoidal output signal having constant voltage amplitude and constant frequency.