THE DESIGN ADOPTED HAS SOPHISTICATED SERVICE FEATURES, DIGITAL DATA SWITCHING ABILITY, AND VARIOUS TERMINAL CAPABILITIES, IN ADDITION TO HIGH RELIABILITY OF SYSTEM PERFORMANCE, MAINTENANCE AND EXPANDABILITY. PCM TIME DIVISION DIGITAL SWITCHING, DISTRIBUTED PROCESSING WITH A MULTIPROCESSOR, AND POWERFUL ERROR-TOLERANT TECHNIQUES ARE UTILIZED TO MAKE THIS SWITCHING SYSTEM COMPETITIVE WITH U. S. PRODUCTS. IN JAPANESE.