The Type 715-A Direct-Current Amplifier is designed to be used as a calibrated d-c millivolt meter or microammeter in the measurement of small d-c voltages and currents. It is also designed for use with a 5-milliampere d-c recorder for the recording of variations of any electrical quantity which may be translated into variations in small d-c currents. The amplifier is completely a-c operated from 115/230-volt, 60-cycle supply. No batteries of any Kind are used.