The clapping of a player not involved on the current scene, or of the moderator, is the common way to signal the currently active players that the current scene should be interrupted, or respectively, that a new scene should begin (e.g., in freeze tag).
The player who clapped comes onto the field of play as quickly as possible and replaces one of the players or sends, if necessary, several of them or everyone off the stage too.
Scene interruptions without clapping are, however, more theatrical and work more elegantly, yet are definitely more difficult to realize. They assume a very attentive, experienced, and well-rehearsed team.
As the players must immediately recognize, on the one hand, that a player is entering the scene, and on the other, they must notice which character should have his/her intervention: Whether he/she wants to interrupt the scene or - without interruption - wants to enter the scene as an active character, a passer-by, or a prop.
by Guido Boyke