The output is controlled by means of a three position illuminated rotary switch. It has a maintained and momentary position, and a center OFF. When turned ON, a relay is energized and the internal lamp is illuminated. The contacts of the relay drive AC voltage directly to one pair of yellow binding posts, and through a full wave bridge rectifier to a pair of red and black binding posts. LED indicators next to the binding posts and near the meter indicate AC or DC mode.
A 10 kOhm load resistor is connected to the DC output along with a 12 volt zener diode and an indicator LED. This provides a 5-20 watt load for the DC output, and indicates if there is an output voltage above about 20 volts as a safety precaution.
This is a small portable AC and DC power supply intended for circuit breaker charging motors and other general purpose applications. It will provide AC and DC voltage in three nominal ranges from 0 to 120, 240, and 480 volts, at 1 kVA. It will be in a suitcase style enclosure approximately 13” x 9” x 12”, and weighs 50 lb.