Once the racquet is back at eye level, the racquet can now fall, or loop down, to the low point of the backswing (one foot below the contact point) before swinging forward.

Based on the level of customer contact between enterprises and customers, the service section has fallen into three categories: high-level, middle-level and low - level companies.

The contact voltage drop was low in the initial stage of wear, then rose to a certain level, finally became stable.