Patent ID: 7884552

Claim:
An electrical discharge tube, comprising: a pair of electrodes arranged to be supplied with a voltage having an alternating component from a power source and to be supplied with heating current from an electrode heating circuit; a tubular member that accommodates the pair of electrodes therein; and a temperature sensor that outputs a detection signal based on the temperature in at least one of the pair of electrodes, the detection signal being arranged to be supplied to a controller that controls the heating current; wherein the electrical discharge tube is a hot cathode tube; the temperature sensor includes a thermocouple; the temperature sensor is disposed in the tubular member; a stem is provided on each of the ends of the tubular member, at least one of the pair of electrodes includes a pair of leads extending from the stem and a filament bridging the pair of leads, and the temperature sensor is attached to at least one of the pair of leads; the temperature sensor includes a first temperature detection element to be attached to one of the pair of leads and a second temperature detection element to be attached to another one of the pair of leads; and the temperature sensor is attached to the at least one of the pair of leads at a position adjacent to the filament.