PURPOSE: To freely set using forms of functional buttons so that various functions are given to the buttons, by rewriting memories of button functions, etc., in private branch exchange equipment.

CONSTITUTION: When an autodial No. setting special No. is inputted through operational buttons 210 of a switch box trunk line 200 after the switch box 200 is set to the program mode, this condition is detected by a button scanning circuit 209 and the switch box 200 is set to setting mode for the autodial No. setting special No. and at the same time, a private branch exchange 100 is set to a condition so that it receives dial No. data. When an autodial No. is inputted by means of an operating board 210 which has a function as an autodial, the No. is written in a memory circuit 106. Finally, when the set button of the operating board 210 is depressed, the button function data and autodial data stored in the memory circuit 106 become effective.