Cabling forms the physical basis for connecting devices. Cabling is realized by means of transmission media that are electrically conductive or light-conducting in order to be able to transmit electrical or optical signals.
Historically, the most suitable proprietary cabling structure has always evolved in parallel with a communications structure. Just think of the telephone cabling with its twisted wires, the 3270 cabling with the RG-62 cable, the AS/400 world with the twinaxial cable or IBM 4700 or 8100 which are wired with twisted conductors. In addition, there is the classic LAN world with the token ring cabling, a cabling based on shielded twisted conductors, the first Ethernet versions with coaxial cables, known as yellow cable and Cheapernet cable.
Since the cabling was tailored to both the network topology and the protocol, this inevitably led to the use of different transmission media. Starting with twisted-pair telephone cable, the range extends to the various coaxial cables with a wide variety of bandwidths, impedances, shielding properties and physical dimensions, to special cables such as the twinaxial cable, and finally to TP cables. In addition, there were new data connectors for each cable type: the BNC connector and the N connector, the twinaxial connector and the TAE connector, the Sub-D connector and the IBM data connector, the ADO connector and the RJ45 connector, and many more.
This situation often led to the use of several networking concepts with different data cables within companies. In this context, one also speaks of legacy cabling, since this proprietary cabling could not be opened up for other network topologies and services at all, or only with a great deal of technical effort.
These inflexible service- and manufacturer-dependent cabling structures were only replaced by the development of flexible application-neutral cabling. This development can be traced back to the change in the requirement profiles of the companies. At the same time, uniform structures developed, which were laid down in the cabling standards. Today, we therefore speak of service-neutral, structured cabling.