Coach/QB Headset Communication

Yesterday I worked a scrimmage and the head coach for appeared to be calling in his plays to the QB from his headset to a speaker in the QB’s helmet, as is common at higher levels of football. Is would appear that this violates Rule 1-5-3c(2). Is that correct, or is this method of communication allowed at the HS level?

This is a violation of NFHS Rules.