SDH 52 156 MB/S (VC-3/4) DIGITAL CROSS-CONNECT SYSTEMS WITH HIT-LESS SWITCHING FUNCTION/

Since 1989, NTT has been introducing the Synchronous Digital Hierarchy (SDH) Transmission System to create simplified, easy-to-operate trans mission networks. Our main task in the future development of telecommu nication networks is to make their operation and management more effic ient. This paper describes the SDH 52/156 Mb/s (VC-3 (Virtual Containe r 3)/4 (Virtual Container 4)) Digital Cross-Connect System (Module AX) . This system enables real-time SDH network operation through cross-co nnection of VC-3 and VC-4 levels. ft includes VC-3/VC-4 remote path-se tting, network-level path restoration for route breakdowns and a hit-l ess switching capability to support relocation of existing telecommuni cation cables. It also supports a standard Q interface and SEMF (Synch ronous Equipment Management Function), and is based on the TMN (Teleco mmunication Management Network) principle. The software for the module is developed through object-oriented design so as to facilitate funct ional expansion.