Twisted-pair cable and pin assignments 159Pin MDI-X signal name MDI signal name8 -48V -48V feeding power (NegativeVport)Note: The plus (+) and minus (-) signs represent the polarity of the wires that make up eachwire pair.Straight-through wiringIf the twisted-pair cable is to join two ports and only one of the ports has aninternal crossover (MDI-X), the two pairs of wires must be straight-through.(When autonegotiation is enabled for any RJ-45 port on this switch, you canuse either straight-through or crossover cable to connect to any device type.)You must connect all four wire pairs as shown in the following diagram tosupport Gigabit Ethernet connections.Straight-through wiring diagramCrossover wiringIf the twisted-pair cable is to join two ports and either both ports are labeledwith an “X” (MDI-X) or neither port is labeled with an “X” (MDI), a crossovermust be implemented in the wiring. (When autonegotiation is enabledfor any RJ-45 port on this switch, you can use either straight-through orcrossover cable to connect to any device type.)You must connect all four wire pairs as shown in the following diagram tosupport Gigabit Ethernet connections.SMBUsing the Nortel Business Ethernet Switch 50 SeriesNN47924-301 01.01 Standard1.00 October 2006Copyright © 2006, Nortel Networks Nortel Networks Confidential.
