PURPOSE: To improve line utilization efficiency and to reduce communication cost by allowing a command reception station side to receive a reservation signal from a command issuing side, reserving an accommodated position of a predetermined extension or trunk from designation reservation management data set and registered based thereon and controlling a general call in a busy state.

CONSTITUTION: A reservation registration section 41 receives reservation registration of a command line based on input information from a command issuing terminal equipment making a simultaneous command and stores input data to a memory in a form of a command reservation management table 42. A terminal equipment idle busy management table 43 has data managing an idle/busy state of an extension/trunk accommodated in a PBX and the data changes dynamically in interlocking with exchange control based on the terminal equipment utilizing state. A control section 44 uses command reservation management data of the table 42 as input information to monitor the state of line with respect to a subscriber of its own station and plural opposite stations while referencing the table 43. When an idle state is detected, the table 43 is set to a busy state and an acquisition enable state is set to an acquisition enable/disable part in the table 42 and idle EN information is set to an accommodation location information part and when a command line to a counter station is acquired, the data are transmitted to the counter station.