CONFERENCE TRUNK SYSTEM

PURPOSE:To attain telephone conference for lots of persons without the operator of the conference telephone set by limiting automatically the number of talkers by the control of a priority selection section when a prescribed number or over of utterance exists at the same time. CONSTITUTION:The priority selection section 6 gives a participation connection signal 9 to all trunk circuits L1-Ln when the number of participants making simultaneous utterance is a prescribed number K or below. Moreover, when the number is K or over, the number K of persons are selected depending on the priority of the participants and a participation connection signal 9 is sent to a participation switch section 8 of the trunk circuit. A conference addition section 12 adds all the incoming voice signals of K-set outputted from a participation connection section 10 and sends the result to a participation switching section 8 as the full addition voice signal S. Then the signal S-Pi being the subtraction of its own voice signal from the full addition signal S is formed and fed to the section 8 via the participation connection circuit 10. The participation connection circuit 10 selects the voice signal S-Pi in receiving the participation connection command signal from the priority control section 6 and selects the full addition voice signal S when said command signal is not received to send the result to the conference participants.