Exchanges are limited: While hand signals are now permitted, players and coaches may only talk during the 25 seconds between points when the player is on the side where the coach is sitting.

US Open Tennis 2024; ... "Subtle, non-verbal ·Coaching, defined as hand signals or gestures that are discreet and do not distract the opponent or fans, ...

Off-court coaching will be allowed in tennis from January 2025, ... Coaches can issue advice either verbally or via hand signals at any time except during the playing of a point.