KEY TELEPHONE SYSTEM

PURPOSE:To change a speaker sound volume by each function. CONSTITUTION:When a function of sounding a speaker 8 under the control of, e.g. a key telephone system Tn is implemented, a main control section 2 references a function sound volume storage section 21 and reads a setting value of a speaker sound volume of the key telephone system Tn corresponding to the function and sends a speaker sound volume setting value to the key telephone system Tn via a key telephone system interface section In. The telephone set control section 5 of the key telephone system Tn receives the speaker sound volume setting value sent from the master set 1 via the master set interface section 4 to control a variable amplifier 6 according to the received speaker sound volume setting value.