Chapter 1 0BIntroduction System framework: Rack 1~rack 8+RTU modules ．．． Remote I/O ． ． ． ． ． ． ． ． ． ． 7 backplanes 7 backplanes ． ． Note: Users are provided with the special cables to connect the extension backplanes. The length of a special cable can be up to 100 meters. They are also provided with the fiber cables which are used with the special adapters. The length of a fiber cable can be up to 2 kilometers. 1-5