What is rule of ampire in table tennis?

Answer 1

For each match there is an umpire, whose primary duty is to decide the result of each rally.

He is also required to exercise judgment in applying some laws and regulations, such as deciding whether a rally should be a let because a player's service or return may have been affected by circumstances outside the player's control, or whether a player's behaviour is acceptable.

An assistant umpire is solely responsible for decisions on edge balls at the side of the table nearest to him, and he has the same power as the umpire to decide the legality of a player's service action, whether a player obstructs the ball and some of the conditions for a let.