Nortel Networks 70 Series manual Straight-Through and Crossover Cables

Installation and Reference for the BayStack 70 Series 10/100 Ethernet Switches

Straight-Through and Crossover Cables

For two devices to communicate, the transmitter of each device must be connected to the receiver of the other device. The crossover function is usually implemented internally as part of the circuitry in the device. Computers and workstation adapter cards are usually media-dependent interface ports, called MDI or uplink ports.

Most hub and switch ports are configured as media-dependent interfaces with built-in crossover ports, called MDI-X or normal ports. Refer to the instructions in Chapter 3, “Installation,” for appropriate cable use and connection.

Figure B-1 illustrates a straight-through twisted-pair cable.

Transmit 1

2

3 Receive 6

MDI port

Twisted pairs

1Receive

3

6 Transmit

MDI-X port

2008.8

Figure B-1. Straight-Through Twisted-Pair Cable

Figure B-2 illustrates a crossover twisted-pair cable.

1

Receive

2

3 Transmit 6

MDI-X port

1Receive

3

6Transmit

MDI-X port

7666EA

Figure B-2. Crossover Twisted-Pair Cable

B-2 206375-A