an improved communication system which allows data , voice , and / or other non - real - time and real - time data streams to be transferred from one station to another over a single telephone line with optimal use of the available bandwidth and with a transparency to data transferring processes such as in computer systems coupled to the station interface devices is disclosed . a local data + voice interface device accepts digital data at a data port , analog voice signals at a voice port , digitizes the voice signals , compresses them , packetizes both the digital data and the digital voice data , identifying for each packet the type of data contained therein , and transmits the packets to a remote data + voice interface device , which separates the packets by their identification , and reconstructs the separate voice and data streams .