Doesn’t look like he has to physically signal

Obviously does when they only have a flag

From IFAB

2.
Assistant referees

Beep signal

The beep signal system is an additional signal which is only used to gain the referee’s attention. Situations when the signal beep may be useful include:

offside
offences (outside the view of the referee)
throw in, corner kick, goal kick or goal (tight decisions)
Electronic communication system

Where an electronic communication system is used, the referee will advise the ARs as to when it may be appropriate to use the communication system with, or instead of, a physical signal.

Posted By: SCC 28, Apr 11, 21:03:07