who can call a time out

[steve g]

I was at a game to day and the coach called time out but it was not given to him and the game ended. What I am asking is who can call a time out and when? I was told that the coaches can only call time outs when there is a whistle and there wasn't one is this right or can a coach call time out, meaning that he personally calls for the time out or does a player on the court have to call it
just wondering
is there a clear answer and if so can i get one