When can the Robocoach begin coaching?

[FRC111]

At what point during the beginning of the match can the Robocoach begin to issue commands to the robot? Can the Robocoach send commands prior to the beginning of the Hybrid period, or must they only begin to transmit once the Hybrid period has started?

[GDC]

The RoboCoach may begin sending signals to the Robot when the Hybrid period starts (as indicated by the arena clock starting to count down the time).