A method and apparatus for protecting an energized inductive device such
as an electromagnet from an open circuit, i.e., the loss of the power
source for the inductive device. A diode is connected across terminals of
the inductive device such that when the inductive device is normally
energized, the diode is reversed-biased. A spark gap enclosed in a
housing is connected in series with the diode. An inert gas fills the
housing. A resistance in the form of one or more resistors is in series
with both the diode and the spark gap. Upon the sudden loss of supply to
the energized device, the diode, the resistance and the spark gap form a
path for the discharge of energy from the inductive device.