TA7104 /7108 Hardware Installation
155/1531-ANF 90114 C 2017-03-08
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The RJ-45 cable uses two pairs of wires: one pair for transmission and the second pair for reception. It
is wired so that pins 1 & 2 are on one twisted pair and pins 3 & 6 are on a second pair according to
common wiring standards which meet the EIA/TIA T568A and T568B requirements.
Figure 7:
Straight through Connectivity
Pin 1
Pin 1
Pin 2
Pin 2
Pin 3
Pin 3
Pin 6
Pin 6
Pin Name and Function
The following is the function of each pin in a RJ-45 cable.
Table 11:
Pin Name and Function
Pin #
Name
Function
1
Transmit Data Plus
Positive signal for the TD differential pair. This signal contains
the serial output data stream transmitted onto the network.
2
Transmit Data Minus
Negative signal for the TD differential pair. This contains the
same output as pin 1.
3
Receive Data Plus
Positive signal for the RD differential pair. This signal contains
the serial input data stream received from the network.
4
not connected
5
not connected
6
Receive data minus
Negative signal for the RD differential pair. This signal contains
the same input as pin 3.
7
not connected
8
not connected
Crossover Cable
A RJ-45 crossover cable is used when only two systems are to be connected to each other, peer to
peer, at the Ethernet Cards by “crossing over” (reversing) their respective pin contacts. An example
would be connecting two computers together to create a network. The crossover eliminates the need
for a hub when connecting two computers. A crossover cable may also be required when connecting a
hub to a hub, or a transceiver to transceiver or repeater to repeater. When connecting a hub to a
transceiver, a straight through cable is always used.
Note:
This is not an IEEE supported configuration and should be used for test purposes only.
A crossover cable is sometimes called a null modem. The colored wires at either end are put into
different pin numbers, or crossed over.
Figure 8:
Crossover Connectivity
