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5.2 10BASE-T Components

Network Medium

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The 10 Mbps twisted-pair Ethernet system was designed to allow segments of approximately 100 meters in length when using modern "voice grade" twisted-pair telephone wiring that meets the EIA/TIA Category 3*1 wire specifications and follows the correct wiring scheme. The maximum segment length at your site may be shorter or longer than this depending on the quality of the twisted-pair cabling in your system. The EIA/TIA cabling standard recommends a segment length of 90 meters between the wire termination equipment in the wiring closet, and the wall plate in the office. This provides 10 meters of cable allowance to accommodate patch cables at each end of the link, signal losses in intermediate wire terminations on the link, etc.

While the 10BASE-T system is designed to use voice grade telephone cable that may already be installed, many sites choose to install higher quality Category 5 cables, connectors, and wire terminating devices to provide data service to the desktop. These higher quality components work well for 10BASE-T and also provide the best possible signal carrying system for the 100-Mbps Ethernet media systems. This approach makes it a relatively straightforward task to increase the bandwidth of your network system when it becomes necessary to accommodate increased network traffic.

There are twisted-pair Ethernet cable testers available that allow you to check the electrical characteristics of the cable you use, to see if it meets the important electrical specifications. These specifications include signal crosstalk, which is the amount of signal that crosses over between the receive and transmit pairs, and signal attenuation, which is the amount of signal loss encountered on the segment.

The 10BASE-T media system uses two pairs of wires, which are terminated in an eight-pin (RJ-45 style) connector. This means that four pins of the eight-pin MDI connector are used.

The transmit and receive data signals on each pair of a 10BASE-T segment are polarized, with one wire of each signal pair carrying the positive (+) signal, and the other carrying the negative (-) signal.

While an eight-pin connector is specified in the standard for making connections to a 10BASE-T segment, you will also see 50-pin connectors used on some 10BASE-T hubs. The 50-pin connector, also called a "Telco" connector, is designed to support the voice grade wire in common use in the telephone industry, and provides a more compact way to connect a set of twisted-pair wires to a 10BASE-T hub.

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Quick Reference Guide to 10BASE-T Twisted-Pair Ethernet - 04 SEP 95

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