4.3 Assistant Umpire
4.3.1 For international competitions an assistant umpire is appointed and he takes over or shares some of the umpire’s duties. For example, 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 players’ service action, whether a player obstructs the ball and some of the conditions for a let.
4.3.2 If either the umpire or the assistant umpire decides that a player’s service action is illegal, that a player obstructs the ball, that the ball in service touches the net or that the conditions of play are disturbed in a way which could affect the outcome of the rally, that decision stands. 4.3.3 Nevertheless, a decision taken by one of these officials may in some circumstances be pre-empted by a decision of the other. For instance, whether or not the ball touches the edge of the playing surface on the side nearest to the assistant umpire may be irrelevant if the umpire has already seen a player move the playing surface. Similarly, a service that is judged illegal by the assistant umpire may not be penalized if the umpire has previously decided that the rally is a let because a ball from another table has come into the playing area.
4.3.4 The assistant umpire should be seated directly opposite the umpire, in line with the net, and at about the same distance from the table.