[BillyMac]

From my pregame:
On double whistles, let’s both hold our preliminary signal and not give a block or player control signal. Make eye contact with each other. Give the call to whoever has the primary coverage, most often the lead official, unless you definitely have something different that happened first, in which case we’ll talk about it.

From Most Misunderstood Rules list:
A defensive player does not have to remain stationary to take a charge. A defender may turn away or duck to absorb contact, provided he or she has already established legal guarding position, which is both feet on the playing court and facing the opponent. The defender can always move backwards or sideways to maintain a legal guarding position and may even have one or both feet off the playing court when contact occurs. That player may legally rise vertically. If the defender is moving forward, then the contact is caused by the defender, which is a blocking foul.