PURPOSE: To confirm the content of a function key set to the function key by providing function keys, a storage means storing information of functions set to the function keys and a display means displaying the function information.

CONSTITUTION: When the operator obtains no information as to the function of a function key 4, a confirmation key 7 of a telephone set 1 is depressed and they the key 4 is depressed. The depression of the keys 7, 4 is informed from a control section 2 to a control section 10 of an exchange 9. The control section 10 extracts the information of the key 4 stored in the storage section 11. This information is sent to the control section 2 of the telephone set 1 and the control section 2 uses the display section 3 to display the setting content of the key 4 to the operator by using the sent information. Thus, the operator obtains the information relating to the key 4 without inquiring about the information to other operator.