Appendix B. Thick and Thin Coaxial Media Systems

This appendix describes the coaxial Ethernet media systems. These were the first media systems used for Ethernet, and were standardized in the early 1980s. Today, the vast majority of Ethernets are based on twisted-pair and fiber optic media, and coax media is considered obsolete for most uses. However, many coaxial systems were built and a number of them are still in use.

We’ll use the same format to describe the coax media systems and cables as do the media and cabling chapters earlier in the book. The first two sections of this appendix describe the 10BASE5 and 10BASE2 media systems. The next section describes how to build and install coaxial cables, connectors, and transceiver taps. The last section describes how to troubleshoot both thick and thin coaxial cable systems.

Thick Coaxial Media System

The thick coaxial media system (10BASE5) was the first Ethernet media system specified in the original DIX standard of 1980. The 10BASE5 media system is limited to 10 Mbps signals, which severely restricts its usefulness as a backbone network, due to incompatibility with higher speed systems. If later you needed to link things together at higher speeds, you would be forced to replace your 10BASE5 media system with twisted-pair or fiber optic cables, depending on the distance you needed to cover.

Rather than go to the trouble of installing a thick coax system only to have to replace it later, virtually all new network installations are based ...

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