Which signal is never repeated by the second referee?

The second referee in volleyball has a specific role during the match, and one key responsibility is to assist the first referee with signals to maintain clarity and communication. The signal for a service fault is unique in that it is primarily the responsibility of the first referee. When a service fault occurs, the first referee signals it and typically does not require reinforcement from the second referee.

In contrast, signals such as "end set/match," "illegal block," and "four contacts" are situations where the second referee often supplements the first referee's calls or ensures that the players and teams are aware of the infraction or conclusion of play. Since service faults are clearly defined and directly managed by the first referee, there is no need for the second referee to repeat this particular signal, thus making it the correct answer to the question.