Like most linear beam tubes having external tuning cavities, IOTs are vulnerable to arcing, and must be protected with arc detectors located in the output cavities that trigger a crowbar circuit based on a hydrogen thyratron or a triggered spark gap in the high-voltage supply.[1] The purpose of the crowbar circuit is to instantly dump the massive electrical charge stored in the high voltage beam supply before this energy can damage the tube assembly during an uncontrolled cavity, collector or cathode arc.[1]