570     6   

   

        -
  ,      -
   .   
     .     -
        
    (Plain Old Telephone Service  POTS) ,  
, ISDN.         -
    . ,     -
     ,   ISDN  
     .        -
 , ,  ,       
ISDN          -
 ,        
 , 11   ISDN.   -
   ISDN       
          ,
     ,       -
     .

       -
     ,   
      .

    ,   .25  frame relay, -
      . 
,         ,   
  ,     ,     -
 .     .25  frame relay  
         
ROBO,         ,    -
    .    -
    .25       
PAD,   ,     .

        -
   ,    
     .    , 
     ,   -
 ,  ,     -
    ,     .
,       ISDN  -
,      64 /   
64 /   frame relay    .

   ,      
         
.        -
   ,       
 .      20-40   -
     ISDN.  ,  