PURPOSE: To control the registration of camp-on multiply from one caller terminal equipment by allowing an exchange controller to monitor a registered called terminal equipment to connect sequentially the called terminal equipment whose busy state is finished to a caller terminal equipment.

CONSTITUTION: When a terminal equipment 11 makes camp-on (CO) registration to a terminal equipment 12 at first, information of a registration terminal equipment 11 and a registered terminal equipment 2 (e.g. each telephone number) is set to a CO registration data table 24. In this case, a registration data number of the table 24 is set to a 1st CO registration area of the terminal equipment 11 of a CO registration state monitor table 23. Succeedingly, when the terminal equipment 11 applies CO registration to the terminal equipment 13, the information of the table 24 is set and the registration data number is set to a 2nd CO registration area of the terminal equipment 11 of the table 23. When the terminal equipment 11 applying CO registration to the terminal equipments 12-14 makes a predetermined operation to the busy state and requests the transfer to a designated terminal equipment or CO release of the designated terminal equipment, a control section 17 starts a control section 18 and clears the tables 23, 24 based on the registration data number set in the table 23 to revise or release the registration.