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"Hub", "Switch" and "PC" defined: A "PC" is a device that
transmits on a pair of wires that use pins 1 and 2 ("1,2"). A "hub" and
"switch" are devices that transmit on pins 3 and 6 ("3,6"). When the
TVR1000 senses a link pulse or data packet, it lights the Data and
Link LEDs on the faceplate to indicate its source (hub or PC) based
on the above standard. "Hub" on the faceplate also means switch.
Link Pulses and Data Packets: LAN devices interact with one
another using Link pulses and Data packets. The TVR1000 detects
and displays both data and link pulses on the DATA and LINK LEDs.
The Link pulses and Data packets are different depending on whether
the devices are 10, 100 or 1000 Base-T devices.
10 Base-T Link pulses and Data packets: 10 Base-T devices
synchronize communication with one another first by each sending
link pulses (a series of single pulses) followed by any data packets
being sent. During quiet time (when there is no data being
transmitted) both devices send link pulses causing the Main Unit's
LINK LEDs to light. The speed and duplex of the link is displayed on
the Speed Verification LEDs.
100 and 1000 Base-T Link Pulses and Data packets: In the 100
and 1000 Base-T environment, a LAN device sends a burst of Link
pulses (containing setup parameters) to the other LAN device. These
bursts continue until acknowledged by the other device (this is termed
"negotiation"). Once the negotiation is complete, data packets are
sent back and forth. No more link pulses are required as long as the
link is not broken. The existence of Link Pulses and Data packets will
cause the DATA and LINK LEDs to light. During link pulse and
data transmission, the link speed and duplex will be displayed on the
Speed Verification LEDs. Notes: Some single speed 100 and 1000
Base-T devices do not send link pulses (just data packets). Also,
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some devices are programmable, allowing you to "force" their speed
and duplex. "Forced" devices, likewise, may not send link pulses.
Because the TVR1000 uses link pulses to determine the speed and
duplex, if there is no link pulse, no speed LEDs will light. This does
not mean that the devices cannot communicate. It means that the
TVR1000 cannot detect the details about the device. Fortunately,
most LAN devices constantly provide link pulses.
Common cable problems: The cable category (Cat 5, Cat
5E, etc.), the number of twisted pairs in a cable and the correct
fabrication of the cable all affect the communication capability of a
network. For instance, 10Base-T only requires two pair cables. Two
standards exist for 100Base-T. One requires two pair cables and the
other requires four wire pair cables. 1000Base-T requires 4 pairs.
If a two pair cable is used when four pair cables is required, a slow
connection will be permanently established. Another common cable
problem is caused by inverted pairs: A pair exists but the pins are
inverted (e.g. 1,2 is 2,1). Make sure you use the proper cable type.
Cat 5E cable is required for 100 MB/s and 1000 MB/s speeds.
LAN type
10Base-T
100Base-T (Type 1 or TX)
100Base-T (Type 2 or T4)
1000Base-T
As is shown in the above table, 10Base-T or 100Base-T (Type 1 or
TX) LAN ports use two pair cables. 100Base-T (Type 2 or T4) and
1000Base-T LANs require all four pairs. It is best to use a minimum
of Cat 5E cables with all four pairs to insure compatibility with all
three types of Base-T LANs.
Cable Pairs Required
1,2
3,6
1,2
3,6
1,2
3,6
4,5
7,8
1,2
3,6
4,5
7,8
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