PURPOSE: To suppress the load in a processor by using a speech time display with an extension telephone set.

CONSTITUTION: The system consists of a period display control section 102 activated by the interruption of one second period, an extension control section 109 displaying the speech time on a telephone set, and communication section 104,107 sending a message from the period display control section 102 to the extension control section 109 in a broadcast form, a display updation notice including a second period counted value incremented every time with the period control section 102 is notified to the extension control section 109 in the broadcast form and the difference from the second period counted value of the extension controller is added to a speech time counter controlled at every extension telephone set and the sum is displayed as a speech time and the received counted value is copied to the second period counter of the extension control section 109.