The scoring of a blow is based on an honor system; it is the responsibility of the fencer being hit to acknowledge a valid attack from the opponent. The fencer who is struck verbally acknowledges the blow by calling out in a loud voice, or in certain types of combat, dramatically acting out the hit for showmanship. No fencing directors, judges or electronic scoring systems are used. The fighting is overseen by a marshal who monitors the bout for safety and fair play from both participants, but is not permitted to judge the validity of an attack. However, the marshal has the ability to warn a fighter in cases where an obvious blow went unacknowledged, usually by politely asking if they are certain they were not struck. In extremely rare cases, the fighter's authorization to fence can be revoked.