Triplett TVR10/100/1000 - Manual (Page 28)

the negotiated speed/duplex of the two devices is slower than the
speed/duplex of each individual device (you determine the speed
and duplex of the individual devices by plugging them separately
into the Green jack as shown in the Single Port test of Example#1).
As an example, if one of the devices is 1000 MB/s, full duplex and
the negotiated speed between the two devices is 100 MB/s, half
duplex, you know that something is pulling the 1000 Base-T device
"down". Note: When you remove the TVR1000 from the circuit,
remember to cable it correctly. In this example it, the two devices
are communicating using the GREEN JACK and the middle jack. A
straight thru patch cable is required.
Analysis of test example #2: When you plug the two LAN devices
into the TVR1000, they attempt to negotiate a common speed and
duplex. If they do not communicate immediately, a crossover cable
could be required. The TVR1000's three jacks provide the flexibility
to quickly create either a straight thru or crossover connection
(depending on the jacks you chose). Follow this procedure: Start by
plugging the two LAN devices into the two leftmost jacks (making a
straight thru connection). For less confusion, it is best to use straight
thru patch cables (we provide you two). Be sure the TVR1000 is
powered ON before any connections are made. Study the DATA and
LINK Pulse LEDs. Each column indicates a DEVICE TYPE (Hub
and PC). The object is to select jacks such that both columns of
LEDs have a LED ON (both hub/switch and PC). If both columns
do not have LEDs on, move the connector plugged into the center
jack to the jack on the far right (making a crossover connection
between the two devices). Once both columns have a LED lit, the
devices are communicating and the required patch cable has been
determined (i.e. if the two leftmost jacks are being used, a straight
thru patch cable is required to make the connection).
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