PURPOSE: To provide the time service in a key telephone set, by incorporating a time counting circuit and a voice synthesizing circuit in the main device of a key telephone device.

CONSTITUTION: When a receiver is hooked off in a key telephone set TEL1 or TEL2 and an extension button or a trunk button is depressed, these information are given to a controller CPU through a data interface DI of a main device 1 and an input/output port I/O. The controller CPU controls a voice switch SW to connect the originating telephone set and the terminating telephone set through the switch SW and a voice interface VI or connect the originating telephone set and a main wire through a trunk TK. When the originating telephone set requests the time service by a button or dialing, the controller CPU starts a voice synthesizing circuit VS and converts time information of a time counting circuit TM to a voice signal and transmits it to the telephone set through the voice switch SW.