Abstract: A digital subscriber terminal equipment is connected to the line circuit at a local exchange via a conventional subscriber line but permits simultaneous transmission of speech and data (e.g., viewdata). The terminal equipment and the line circuit each contain a central unit, a direction-separating unit, and a 10-bit data bus; the terminal equipment also includes a codec with a filter. The central units control the writing and reading of the digital signals into and out of the data bus and form on the subscriber line a main channel for data or speech, an additional channel for control, and an additional data channel.