"Tip" mechanic

[La Rikardo]

In the frontcourt, A1 passes the ball toward A2. B1 gets a hand on the pass and deflects the ball into the backcourt. A1 runs into the backcourt and controls the ball.

When are we supposed to give the "tip" mechanic to indicate that B was last to touch the ball in the frontcourt? Do we do it when the ball gains backcourt status or do we wait until A1 touches the ball? Is this mechanic supposed to be a message to Team A that they may touch the ball without violating or is it supposed to be used to clarify our no-call when A1 touches the ball?

I would think we're supposed to do it when the ball gains backcourt status, but I can't find anything that explicitly says that.