If you are referring to call forward this all depends on how they are setting up call forwarding. If they are pressing the call forward button on the phone then the phone will not ring. The call is forwarded directly to the number they entered. There is no setting that will delay the forwarding of a call when the call forwarding button is pressed.
If you want a call to forward to another number if unanswered then the administrator must do this. It is configured on the line settings in the <b>Forward No Answer</b> fields.