One difficulty In the game, each side is allowed to one challenge (regardless of whether the challenge is successful). To overturn the event as called on the floor, like with all replay reviews, there must be clear and compelling visual proof that the call was erroneous. The only way to do this is by getting another review from the video monitor judge or through a timeout. Since the NBA does not use a third ref for flagrant 1 penalties, they can only give out one suspension for excessive contact during a free throw attempt. If a player continues to touch the ball after being called for a foul, he will be issued a second violation and a second suspension. The most common type of challenge in the NBA is the coaching challenge. There are two types of coaching challenges: those based on position and those based on personal conduct. A team can challenge any non-essential call made by an official during gameplay. If the reviewing crew agrees with the assessment of the first review, then no further review is needed. However, if the first review determines that a mistake was made, then the case will go to a second review by a different crew member. This process can be repeated until either the coaches agree that the call was correct or three separate reviews confirm that the call was incorrect. A team can also challenge a personal foul judgment call. These challenges must be received by the referee before the end of the period.