Chapter 9. Fast Ethernet Twisted-PairMedia System (100BASE-TX)

The 100BASE-TX twisted-pair media system is the most widely used Fast Ethernet media type. The 100BASE-TX standard is based on the twisted-pair specifications first developed for the FDDI TP-PMD (Twisted-Pair Physical Medium Dependent) standard. The system operates over two pairs of twisted-pair wires: one pair to receive data signals and the other pair to transmit data signals.

This chapter describes the signaling and media components used in the 100BASE-TX system. We also describe how a station is connected to a 100BASE-TX segment, and provide the basic configuration guidelines for a single segment.

100BASE-TX Signaling Components

The following signaling components may be used in the 100BASE-TX system to send and receive signals:

  • Ethernet interface with a built-in 100BASE-TX transceiver.

  • Medium-Independent Interface (MII).

  • External 100BASE-TX transceiver, also called a physical layer device (PHY).

100BASE-TX Ethernet Interface

A 100BASE-TX interface may be equipped with a built-in 100BASE-TX transceiver used to make a direct connection to the twisted-pair segment. If the interface is equipped with a 40-pin MII connector, external transceivers can be used. Figure 9.1 shows a network interface card designed to be installed in a desktop computer.

100BASE-TX Ethernet interface

Figure 9.1. 100BASE-TX Ethernet interface

The card is equipped with an RJ-45-style ...

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