Backbone Cabling

The next subsystem of structured cabling is called backbone cabling. (Backbone cabling is also sometimes called vertical cabling, cross-connect cabling, riser cabling, or intercloset cabling.) Backbone cabling is necessary to connect entrance facilities, equipment rooms, and telecommunications rooms and enclosures. Refer to Figure 2.7 later in the chapter to see backbone cabling that connects an equipment room with telecommunications rooms. Backbone cabling consists of not only the cables that connect the telecommunications rooms, equipment rooms, and building entrances but also the cross-connect cables, mechanical terminations, or patch cords used for backbone-to-backbone cross-connection.

Permanent Link vs. Channel Link

ANSI/TIA-568-C defines two basic link types commonly used in the cabling industry with respect to testing: the permanent link and the channel link.

The permanent link contains only the cabling found in the walls (horizontal cabling), one transition point, the telecommunications outlet, and one cross-connect or patch panel. It is assumed to be the permanent portion of the cabling infrastructure. The permanent link is illustrated here:

The channel link includes the basic link, as well as installed equipment, patch cords, and the cross-connect jumper cable; however, the channel does not include phones, PBX equipment, hubs, or network interface cards. Two possible channel link configurations are shown here; one is the channel link for a 10Base-T Ethernet workstation, and one is for a telephone.

KEY TERM: cross-connect

A cross-connect is a facility or location within the cabling system that permits the termination of cable elements and their intereconnection or cross-connection by jumpers, termination blocks, and/or cables to another cabling element (another cable or patch panel).