The Hewlett-Packard Model 738A Voltmeter Cali- brator is a compact, completely self-contained, precision generator for calibrating high-impedance electronic voltmeters, oscilloscopes, etc. Special design assures accurate and reliable calibrating voltages from 0.3 millivolt up to 300 VOlts, in precision steps. Accuracy of output attenuator is within ±0.1% or ±5 Jlvolt, whichever is greater, when loaded by a meter with an input impedance of 3 megohms. No operating adjustments are re- quired, other than weekly standardization. The I/ifJ Voltmeter Calibrator consists of two sepa- rate inter-connected units mounted on one small rack panel. The voltage generator section includes a regulated power supply which produces the 300 volts dc working standard, a conventional low distortion rc oscillator with AGC, and a stabilized amplifier which generates the 400 cycle 300 volt rms working standard. The 300 volt peak-to-peak voltage is derived from the 300 volt rms voltage through a resistive network. The type of voltage required is selected by a simple output selector and fed to the attenuator section.