For example, Station A has activated call forward feature to Station B, Station B to Station C, and Station C to Station D. In this case, if Station A gets an incoming call and forwards the call to Station B, then Station B forwards the call to Station C, and Station C forwards the call to Station D. Eventually the call is answered by Station D, which transfers the call to Station A. The call continuously rings at Station A and is not forwarded to Station B.