Direct Current Output (+ D.C. -): Provides a variable DC voltage from 0 to 300 V DC (maximum current 60 mA). Variable Alternating Current Output (A.C.): Provides a variable AC voltage from 0 to 220 V AC. Fixed Heating Voltage Outputs (6.3V A.C.): Provides a fixed AC voltage of 6.3 V to power the filaments in vacuum tubes, with a maximum total current of 4 A. Control Knob (VOLTS): For controlling the level of the variable output voltage. Overload Indicator (O/LOAD): A pilot lamp that lights up upon contact or exceeding the load. To reset, turn off the device for one second and then turn it back on.