PURPOSE: To share one line by plural digital multi-functional telephone sets in the case of using both 2B channels with a voice channel by a private branch exchange and using the digital multi-functional telephone sets only with a voice communication function.

CONSTITUTION: This telephone set is provided with an adjacent telephone set interface part 13 for controlling the transmission/reception of 2B+D multiple signals and control signals between adjacent telephone sets, a B channel selection/communication control part 14 for selecting one of the 2 B channels and performing control required for voice communication to it and an incoming call acquisition control part 15 for mutually transmitting/receiving the control signals through the adjacent telephone set interface part 13, controlling a D channel control part 5 and the B channel selection/communication control part 14 and acquisition controlling an incoming call.