Resistor inserted into a circuit to compensate for current changes (as those arising from temperature fluctuations) [syn: ballast resistor]
B-300-G by NEC and unknown Soviet made.
Tube filled with pure hydrogen and thing iron wire inside. When iron wire is cold, the resistance is low. When temperature rises, the resistance is bigger. The difference of cold and hot resistance is about 10 times. The current going threw berretter heats the iron wire. So the current in working range is stabilized. Used in older equipment. Sometimes in filament circuit in series to tube heaters. In modern time barretter can be replaced with PTC thermistor.
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