"Ringback" is the tone you hear when you're calling someone to let you know that their phone is being rung. (You're not yet connected tot them, so you can't hear the actual ring signal being sent to their phone.) Ringback is generated by the telephone company central office you're making the call from.
What exactly is it that you want to do? (Create a free account, so you can answer in the thread and keep the discussion flowing.)