PURPOSE: To automatically release the setting of call back by enabling the setting of a call back setting time.

CONSTITUTION: When a call back request time is set by dial button operation of caller terminal equipments 10, 20, a central controller 100 receives it storing and registering it in time setting storage area 40 of a main storage device 60. When the time setting is registered, a timer 110 sends an elapsed time to the central controller 100 every prescribed time of a timer 110. The central controller 100 counts a time stored and registered in the setting time storage area 40 and starts a call back setting release means 120 in the main storage device 60 when the count reaches 0.