Circuit for conference telephony

Claim 1

A circuit for conference telephony by the use of a multiple-station communication network wherein digital signals representative of voice data of a conference are transmitted on communication cables and are located within frames which are periodically repeated on a time axis and a plurality of stations are allowed to transmit signals which occupy regions within the frames on a time sharing basis to effect transmission of digital signals, the circuit characterized by receiving logical circuit means for determining whether received voice data is for the conference and for providing timing control signals, at least two buffer memory circuits of identical configuration for reading and writing each of said frames of voice data transmitted from member stations of conference telephony alternately, each buffer memory circuit including receive data memory coupled to the receiving logical circuit means for memorizing the voice data transmitted from the member stations in the order of transmission through the communication cables and at a rate synchronized with transmission speed of the voice data during writing, and means coupled to the receiving logical circuit means for causing the voice data to be read out of the receive data memory repeatedly in fixed amounts during reading, the circuit also characterized by means coupled to the receiving logical circuit means for alternately causing reading and writing by the buffer memory circuits for each frame of voice data, means for D/A converting, on a time sharing basis, said voice data from said member stations of conference telephony read out of said buffer memory circuits, and means for adding said voice data.