3Com 7600 manual 10 or 100 Mbps Speed, 2Cable Support by Transceiver Type

11-4CHAPTER 11: ETHERNET LANS AND BRIDGES IN THE 7600 CARD

10 or 100 Mbps Speed

The 7600 Card can communicate with either a 10 Mbps or in a 100 Mbps communication rate. This capability is available for the Tx port type only. The Fx ports communicate in 100 Mbps only. The Tx ports also have a speed auto-negotiation capability. When speed auto-negotiation is selected, the speed in which the 7600 Card chooses to operate is determined by the communication speed available in the device with which it is communicating. If the device with which it communicating also has a 100 Mbps speed (such as another 7600 Card) then it communicates in 100 Mbps, otherwise it communicates in 10 Mbps. The Fast Ethernet uses a lower bit-time(the time duration of each bit transmitted), but leaves the remainder of the Ethernet CSMA/CD unchanged.

Cabling Fast Ethernet supports structured wiring composed of category 3, 4, and 5 unshielded twisted pair (UTP), 150 ohm shielded twisted pair (STP) and fiber. These media specifications cover almost all cable types currently in use. Equally important, all supported media types can be mixed together and connected through a repeater or switch, just as with the earlier Ethernet media types.

To support these various wiring types, Fast Ethernet provides three transceiver types. A transceiver is that portion of an adapter containing the analog circuitry necessary to transmit and receive data on a physical cable. In Table 11-2, each transceiver type supports a different set of cable applications. It lists two twisted-pair-type transceivers and one fiber transceiver. These three Fast Ethernet transceiver technologies are complementary. The 7600 Card module uses the STP and fiber cable types.

Table 11-2Cable Support by Transceiver Type

Transceiver type	Cable type	Number of	Notes
		pairs (fibers)
100BASE-T4	Category 3 UTP	4	Workhorse design
	Category 4 UTP	4	for category 3 cable,
	Category 5 UTP	5	100-m link span
100BASE-TX	Category 5 UTP	2	Only needs two
	150 Ω STP	2	pairs, 100-m link

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