Abstract: A single international standard integrated services digital network (ISDN), basic rate interface (BRI) is arranged so that either a data terminal and two voice terminals, three voice terminals, or four voice terminals can be operated simultaneously through the interface. Code converters, associated with the voice terminals and with a central office switch, convert eight-bit voice sample code from either the voice terminals or the central office switch to four-bit voice sample code in the interface to enable the bit streams of two voice terminals to be merged for transmission through a single B-channel at the interface. When two voice terminals are operated simultaneously through one B-channel, each of those terminals positions four-bit coded voice samples in a different sub B-channel of the B-channel and stuffs four bits in the other sub B-channel.