Abstract: This invention relates to an electric supply circuit for a large number of multi-phase a.c. apparatus, particularly hysteresis motors of gas centrifugal machines, having circuits to form three-phase control pulses, control circuits for the through-connection between d.c. forms of the desired alternating voltage for one or a number of apparatus to be energized under the control of the control pulses and circuits for adapting the signal levels of the control pulses to the circuit for the formation of the alternating voltages, wherein a large number of circuits for the formation of the alternating voltage is controlled from a single control circuit.