Name of The Calling Feature for Redialing a 'No Answer'

On some systems what is the name of the calling feature like busy redial

where your call reaches a no answer ringing and you want to be alerted when there is somebody at the number that could take your call?...

So after they use the telephone you are alerted somebody might be there.

Or when they pick up the telephone for a call you are alerted somebody can answer when you call now.