(57) A control circuit for electrical contactors, starters and the like which include one or more pairs of separable main contacts is controlled by an electromagnet assembly 10. In order to reduce, if not eliminate, audible noise generated by the electromagnet assembly, the electrical current to the electromagnetic assembly is regulated to minimize the rate of change of magnetic flux therethrough to thereby reduce, if not eliminate, audible noise. The circuitry is also adapted to compensate for alternating current (AC) magnetic coupling from the main poles in order to provide a relatively larger hold in force when the contacts are to remain in a closed position. Apparatus for calibrating an electrical device is taught. A precision power supply device PCS is interconnected by way of appropriate input channels to the device 10 to be calibrated for supplying a precise accurate calibration variable as an input. A personal computer PC is interlinked by way of a communications network CONI with the apparatus 10 to be calibrated and is also interlinked with the precision supply device so that the personal computer PC has available the exact value of input variable utilized. Upon command, the personal computer PC instructs the device being calibrated to deliver to the personal computer PC those values of input variable which the device being calibrated interprets as the input variable value. The personal computer PC compares this value with the actual value and generates a correction factor which the personal computer PC sends back to the device being calibrated for storage in an EEPROM. A power supply 202 which includes a rectifier input circuit MCR1 which provides either half wave or full wave rectified electrical current at an instantaneous voltage value to the input terminal of a controlled switch MQ3 is taught. The controlled switch is controlled by the combination of a "low voltage reset" device MU6 and a field effects transistor MQ2 combined to form a voltage sensing and switching circuit SSM which is interconnected at its input between the input terminal of the voltage regulator and ground and at its output or reset terminal to the control terminal of the voltage regulator. The output terminal of the voltage regulator is connected to the anode of a diode MCR7, the cathode of which is connected to one side of a storage capacitor MC6.