Installation guide

Page 3-3
INSTALLATION
3.4 CONNECTING CABLES
In a typical application, the MR9 connects up to eight Ethernet
devices to the Ethernet network. One port connects the repeater to
the network while the other ports connect to Ethernet devices such
as PC network interface cards. Usually, Port 9 is used as the
connection to the network. In operation, Port 9 is the same as any
other port; you can use any port for the network connection.
Port 9 does have features which make it unique. On the MR9T-C,
where Port 9 is a BNC connector, you can select the internal 50 ohm
terminator and eliminate the need for connecting the cable with a tee
connector and external terminator. On the MR9T, where Port 9 is an
RJ-45 connector, you can select between a straight-through or a
cross-over pin configuration.
3.4.1 Cross-Over and Straight-Through
Twisted pair wires have two sets of polarized signals: TX+ and TX-,
and RX+ and RX-. When you connect any two 10BASE-T devices, you
must make sure that the RX pair of one device connects to the TX
pair of the other device as shown in Figure 3-2.
MR9T
Repeater
10BASE-T
Transceiver
RX+
RX-
TX+
TX-
RX+
RX-
TX+
TX-
Figure 3-2. 10BASE-T Signal Pairs
When you connect a transceiver to a repeater, or a transceiver to a
network hub, the pin configurations of the mated RJ-45 connector
and port must maintain the correct signal pair connections. Since a
repeater needs to be able to connect to both a hub (network) and a
transceiver, Port 9 on the MR9T has a configuration switch that lets
you change the port’s pin configuration. When the configuration
switch is set to the straight-through position (=), Port 9 can connect
to the network hub or to another repeater. When set to the cross-over
position, Port 9 can connect to an Ethernet device such as a