1-3. The Model 415B High Voltage Power Supply is a stable well regulated source of dc voltage. The Model 415B is capable of providing 0 to 3100 volts dc and 0 to 30 milliamperes current. The output voltage is adjustable in steps of 500, 100, 10 and 1 volt by front panel step switch controls. A vernier control provides a means of fine adjustment within the one volt steps. Output power is available from both a front and rear panel high voltage connector, type UG931/U, Output voltage polarity may be switched by a front panel control to provide either a positive or negative output with respect to chassis ground of the instrument. 1-4. The power supply is provided with an overcurrent protection circuit to prevent damage to the instrument in the event of overload or accidental short circuit at the output. Normal operation is quickly restored by a manual reset control following removal of the overload. 1-5. The Model 415B combines the best features of electron tubes and solid state components in a hybrid circuit. The improved reliability and temperature stability characteristics of silicon transistor amplifiers and rectifier diodes together with the high voltage handling characteristics of vacuum tubes provide a dependable, low noise level, highly regulated output. Applications of the Model 415B include calibration of voltmeters and powering of photomultiplier tubes, high voltage klystrons or other devices with current requirements up to 30 milliamperes.