[Back In The Saddle]

Ref in PA's summary is pretty accurate as I recall. The reason for blowing your whistle before play begins is to alert everybody that play is about to begin. We don't want to surprise anybody. After time outs and quarter breaks is an obvious time to use it.

IMHO there may be other times when it would be helpful too. So don't withold an obviously helpful whistle just because the mechanics manual doesn't say to do it. I have seen it used to great effect in very noisy gyms and in lower levels of play. On the other hand, overusing the whistle would, I think, tend to reduce its effectiveness.