SHUNT REGULATORS use a variable resistance placed in parallel with the load. Regulation is
achieved by keeping the resistance of the load constant. Characteristically, the resistance of the shunt
moves in the opposite direction of the resistance of the load.
VR-TUBE REGULATORS are shunt regulators that use a cold cathode as a variable resistance in
parallel with the load. Because of their ability to maintain a constant voltage potential between their plates
and cathode, glow tubes can be connected in series to regulate any voltage. Additionally, glow tubes can
be used to deliver different voltages to different loads.
SIMPLE ELECTRON TUBE REGULATORS use the dc plate resistance of a triode as a variable
resistance in series with the load. The resistance of the vacuum tube is varied by changing the amount of
conduction of the tube. This is done by holding the control grid voltage at a constant level and allowing
the cathode voltage to vary with the output voltage.
The AMPERITE VOLTAGE REGULATOR or BALLAST TUBE is normally used to control
current surges. This is done by heating an iron wire in a hydrogen-filled envelope. The hot iron will
present a large resistance to current flow.