242     3     

    ,   MAC,  
 AUI,        .

   (PHY) ,   ,  
 (. . 3.20):

    ,   

 MAC     4/5  8/6 (  

  Fast Ethernet);

        -
  (PMD),      -
    ,  NRZI  MLT-3;

  ,     -
      , ,
   (   -
).

        -
    MAC   PHY.   -
    AUI  Ethernet   ,
  AUI     
 (       -
    )    -
  ,       MAC  
 ,    Fast Ethernet   FX,   4.

      AUI  40 ,  
    . ,    , -
  5 .

  lOOBase-FX   ,
 

     Fast Ethernet  
        
   FDDI.     FDDI,  
     ,    (Rx)
   ().

  lOOBase-FX  lOOBase-TX   , 
         -
 lOOBase-FX/TX.

    Ethernet    10 /  -
        ,  -
 Fast Ethernet      4/5.   
     FDDI      -
 lOOBase-FX/TX.     4   
MAC ( )  5 .   -
          
    .   -
     ,  
    lOOBase-FX/TX.