The EDC Model 4701A is a controller and Voltage Source which is used in conjunction with the E.D.C. Model 4702A current source. The resultant two unit system forms a wattmeter or watt-hour meter Calibrator with independent control of frequency, voltage amplitude, current amplitude and phase angle. The system may be controlled manually with the 4701A front panel controls or via the IEEE-488 bus. The 4701A accepts an optical pickup input for timing of a preset number of meter disk revolutions, or a TTL pulse input from an electronic watt-hour meter. The system has a specified accuracy and is traceable cells to the National Institute of Standards and Technology. The system is overload and short-circuit proof.