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Specifications and recommendations for Twisted-Pair Ethernet cable
  
     
      The Ethernet adapters have a small, snap-in
      RJ45 connector. 

      RJ45 cabling is also known as Twisted-pair Ethernet (TPE),
      Unshielded twisted pair (UTP) and 10BASE-T.

      This document covers the following topics:
      -  Recommended cables
      -  Cable and connector pinouts
      -  Connecting two workstations without a hub
      -  Link integrity
      -  Common problems

      For more information on the 10BASE-T specification, contact
      your local network supplier or call the IEEE (800-678-IEEE).


   Recommended cables
   ==================
      The RJ45 connector can use 22, 24, or 26-gauge UTP
      cabling. The cable must comply with the IEEE 802.3
      10BASE-T standard.

      If you're using TPE cabling in an residential environment,
      you must use a shielded cable.

      The cable between the computer and the hub must be
      less than 100 meters long.

      If the inter-repeater link distance is more than 300m, please
      insert "Stop backoff on CRS 0" as a command line parameter in
      the net.cfg file.
     
      These UTP cables work well:
      ------------------------------------------------------
      Manufacturer       Model number         No. of pairs
      ------------------------------------------------------
      Belden             9562                 2
      ------------------------------------------------------
      Data Set           2402                 4
      ------------------------------------------------------
      Belden             9566                 6
      ------------------------------------------------------

      Silver satin is not within the 10BASE-T specification and
      cannot be used.  If used, it may not work at all, or may give
      intermittent results.

      The Ethernet adapters do not support pre-10BASE-T concentrators.


   Cable and connector pinouts
   ===========================
      If you need to repair a cable or provide connectors
      for UTP cable, wire straight through as shown in the
      following table.

      Use only four of the eight pins. Pins 1 and 2 must be
      a pair, and pins 3 and six must be a pair.

                   Function    Pin#               Pin#
                   -------------------------------------
                      TX+        1    <-------->   1  
                      TX-        2    <-------->   2  
                      RX+        3    <-------->   3  
                      RX-        6    <-------->   6  
                   -------------------------------------

      To allow for a straight-through cable, the hub provides an
      internal transmit/receive crossover function. This means the
      transmit circuit of the network card is connected to the
      receive circuit of the hub and vice versa.


      Pinout for the RJ45 connector
      -----------------------------
                 ----------              --------------------------
              1 |--        |          8 |------------              |
              2 |--        |          7 |------------              |
              3 |--         ---       6 |------------              |
              4 |--            |      5 |------------              |
              5 |--            |      4 |------------              |
              6 |--         ---       3 |------------              |
              7 |--        |          2 |------------              |
              8 |--        |          1 |------------              |
                 ----------              --------------------------
                    END                             TOP
    
      Pin name and function:

      1  Transmit Data Plus. The positive signal for the TD
         differential pair. This signal contains the serial output data
         stream transmitted onto the network.
 
      2  Transmit Data Minus. The negative signal for the TD differential
         pair. This contains the same output as pin 1.
 
      3  Receive Data Plus. The 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. The negative signal for the RD differential
         pair. This signal contains the same input as pin 3.
 
      7  not connected
 
      8  not connected
 

   Connecting two workstations without a hub
   =========================================
      10BASE-T uses a star topology. This means there is a hub or
      concentrator in the center of a star and each workstation or
      server is connected to this hub.
     
      For TEST purposes, you can directly connect two workstations or a
      workstation and a server without using a hub. This requires a special
      cable that incorporates the crossover function talked about at the
      beginning of this document.
    
                 Function    Pin#               Pin#   Function
                --------------------------------------------------
                   TX+        1    <-------->   3        RX+
                   TX-        2    <-------->   6        RX-
                   RX+        3    <-------->   1        TX+
                   RX-        6    <-------->   2        TX-
                --------------------------------------------------
 
      NOTE: This is not an IEEE supported configuration and should be used
      for test purposes only.


   Link integrity
   ==============
      For 10BASE-T networks, Link integrity (LI) needs to be on. Some
      transceivers, Ethernet cards, or other network devices allow you to
      turn it off, but Link Integrity is always on with most Ethernet
      adapters.
    
      If you're using a transceiver to go to a thick/thin Ethernet segment,
      Link Integrity must be set to on for the transceiver.


   Common problems
   ===============
     
      A hub can't "see" a workstation
      -------------------------------
      This is often caused by a crossed wire in the cable or wiring closet.
      Check to make sure the wiring is correct.


      Workstations can't connect to the network
      -----------------------------------------
      If your workstations are having problems connecting, reset or power
      off/on your concentrator or hub.


      Polarity problems
      -----------------
      A common problem in 10BASE-T wiring is crossing the positive and
      negative phases of the transmit or receive signals. For example, a
      problem would occur if pins 1 and 2 were crossed. (TX+ connected to
      TX-).
 
      The current EtherExpress adapters automatically detect this problem
      and adjust for it internally. Early Ethernet cards did not
      have this feature.
 
      Even though the current Ethernet adapters can take care of this
      crossover for you, it is best to check your wiring and correct this
      problem if you find it.
 

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