SUBSCRIBER LINE TRANSMISSION SYSTEM OVER COPPER PAIR CABLE.

This paper summarizes recent Japanese research and development activities on digital subscriber loop transmission over copper pair cable. Among the various transmission schemes applicable for two-wire bi-directional transmission, the burst-mode time separation scheme (time compression multiplexing) is adopted. Recent activities have placed emphasis on the development of LSI devices to realize cost effective, low power consuming, and compact sized DSU/OCU (Digital Service Unit/Office Channel Unit) equipment, which terminate TCM transmission. Line termination circuits, which include sophisticated analog circuits to compensate for variable loss over subscriber loops and adverse effects caused by bridged-taps, have been studied. As a result, one chip realization employing CMOS technology is expected to be completed by the end of 1983. This LSI together with a digital LSI for circuit termination constitute the key components in the DSU/OCU equipment to be used for the INS field trial scheduled by NTT in 1984.