3Com Corporation
               EtherDisk Diskette for the EtherLink/MC Adapters

                        Physical Transmission Options



 The EtherLink/MC TP adapter has six options that control data transmission
 on the physical medium.  These options are set by moving jumpers on the   
 adapter.                
 
 This file contains information to help you set these options so that
 the EtherLink/MC TP adapter will work correctly with both 10BASE-T and
 non-10BASE-T hubs.  For more detailed information, refer to the
 EtherLink/MC TP Adapter Guide.
 
 
 Setting Jumpers on the EtherLink/MC TP Adapter
 ----------------------------------------------
 
 If you need to change the jumpers on the EtherLink/MC TP adapter to
 accommodate different hubs or wiring:  
 
 1.  Set the IMPEDANCE jumpers to match the characteristic impedance of
     your twisted-pair cable.
 
     a.  Use a test device to verify the characteristic impedance of your 
         cable from the wiring closet to the station.
 
     b.  Choose the impedance jumper setting closest to that         
         characteristic impedance.
 
         Default Setting:  100 ohms
 
         Alternative Settings:  75 ohms, 150 ohms
 
 2.  To set the RECEIVE THRESHOLD, LINK BEAT, EQUALIZATION, TRANSMIT LEVEL,
     and DC SIGNAL jumpers, refer to Table 1.         
 
 
 Table 1.  Jumper Settings for 10BASE-T and Non-10BASE-T Hubs
           --------------------------------------------------
 
              |           |                | HP StarLAN 10,   |
              |           |   SynOptics    | AT&T StarLAN 10, |
              | 10BASE-T  |   LattisNet    | DAVID Systems    | BULL Hub 10
              | (default) | (non-10BASE-T) | (non-10BASE-T)   | (non-10BASE-T)
 -------------+-----------+----------------+------------------+---------------
 Link Beat    |    ON     |       OFF      |        OFF       |      OFF
 -------------+-----------+----------------+------------------+---------------
 Equalization |    TX     |       RX       |        TX        |      RX
 -------------+-----------+----------------+------------------+---------------
 DC Signal    |    OFF    |       ON       |        OFF       |      OFF
 -------------+-----------+----------------+------------------+---------------
 Transmit     |           |                |                  |
 Level        |    NORM   |       LOW      |        NORM      |      LOW
 -------------+-----------+----------------+------------------+---------------
 Receive      |           |                |                  |
 Threshold    |    NORM   |       LOW      |        NORM      |      LOW
 -------------+-----------+----------------+------------------+---------------
 
 
               
                   (%VER  Physical Transmission Options v3.4a)