Triplett TVR10/100/1000 - Manual (Page 35)

Appendix A. Wiring Primer.
Twisted Pair Cable: Base-T LANs are based on a star topology
(every PC on the network is linked to a central location). The central
location is termed a hub or switch. The cabling is always twisted
pair wire terminated with 8 position modular connectors (RJ45).
PC and Hub/Switch defined: A “PC” transmits on a pair of wires
that use pins 1 and 2 (“1,2”). A “hub” and switch transmits on pins 3
and 6 (“3,6”). The TVR1000 bases its testing on this standard.
Cable types: A "straight thru" cable connects a PC to a hub and
does not change the wiring of the cable (e.g. pins 1 and 2 are con-
nected to pins 1 and 2, etc). A "crossover cable" swaps the transmit
and receive pairs of the connection (pins 1 and 2 are connected to
pins 3 and 6). The TVR1000 includes two straight thru patch cables.
Connecting Devices: Base-T devices (PCs/hubs/switches) are
connected together by connecting the "Transmit pair" from one
device to the "Receive pair" of the other. A “PC” transmits on pins
1 and 2 (“1,2”). A hub and a switch transmit on pins 3 and 6 (“3,6”).
Because of these pinouts, a PC connects to a hub or switch with a
straight-thru cable. It follows that two hubs or switches connected
together require a crossover cable (the same is true for two PCs
connected together).
Autocrossover: Some devices adapt them-
selves to either straight thru or crossover configuration, depending
on what is required. During Single Port Testing, the TVR1000 will
light LEDs in both the "PC" and "Hub" columns if a device has
autocrossover capability.
Number of pairs: All 10 Base-T and most 100 Base-T devices
(called 100 Base-TX) use 2 pairs to function but 100 Base-T X4
devices and all 1000 Base-T devices require 4 pairs.
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