To provide the method for controlling an incoming call in busy state by which an off-hook ring service is attained to identify a telephone caller arrived during a busy state.

When a key-phone telephone set shown in the left side in Figure makes a phone call to a key-phone telephone set shown in the right side in Figure, a key-phone master set receiving dial digits allows the called key-phone telephone set to display 'CALL FROM 102'. Since the called key-phone telephone set is busy in this case, the caller key-phone telephone set hears at first a busy tone. When an OHR button of the caller key-phone telephone set is operated, the key-phone master set sensing the OHR button signal instructs an off-hook ring to the called key-phone telephone set. Furthermore, simultaneously the caller key-phone telephone set hears a ring back tone and a 'CAMP ON TO 103' is displayed on its display section. That is, since the off hook ring is made and the caller telephone number 102 is displayed on the called key-phone telephone set, the called telephone set immediately recognize from whom the telephone call comes.