478     6 '  _________________________________

pax        ,  
   .

     1   -
   23 ,  24-     , 
     .   
 ,       24 , 
     56 /.  -
          (bit
robbing).

  4-  1    2  
DS-1 -    ,   DS-2 (
  4-   DS-1)  12  -
,       ,     -
. ,  DS-3   7  DS-2, 
 .

       G.700-G.706. 
 ,       .  ,  -
      4    -
  .      1    
2   32.        30  
  64 / .

     64 / (56 /) 
 1/1.     (fractional)  1/1.  
    -  .

   PDH    :

 ,    - .  -
     1/1     
   RJ-48.       
    1,544/2,048 /.   
:   1    B8ZS,   El 
   HDB3.      1 
 1800  ( )     
.

       -
  2/2  4  1/1.    /  -
   ,  - , 
 .

      -
 G.703,      
 ,    1.    
 1.

 ,      PDH 
 .

       -
    .   -
,    ,      
       -
    .     -