7-8 - ().
(- "" ) , .. . 7-8 / 128 (27) 256 (28) . 48-50 .
, , 56 / (8 ´7 /) 64 / (8 ´8 /).
.1-7.
.1 -7. -
-
, , (- - ) ().
.1-8. -
. 1-8. - . 1-1 "-", - . .
. - , , , ( - ). , , , .25 Frame Relay (FR), (, ), : PAD ( .25) FRAD ( FR).
, , , "-", "-" ( .. - ). , . 1-9 : - "D", 5- (.1-9), - "5", 7- ASCII (.1-96) 8- - . - 1,5 ( 2) "-".
.1-9. - ( ) () ASCII ()
- - , . : "" . "" ( idle sync), , .
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/ :
/ , / (, ASCII EBCDIC, );
/ , , , : (HDLC), (SDLC) , , : AMI, HDB3, 4/5, 8/10 .
/ / / , : (ARQ), (PC), (CRC), - / (FCS), / (FEC) .
, , - , , , , . - , . - .
() , , , - . , - , .
(PC, CRC, FCS, ECC, FEC). , , - , . . - , (PC, CRC, FCS) , - (ECC, FEC). - .
- ( - - - ) ( - , ).
.. , - , / , , :
;
() ;
;
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("1"/"0") .
=2, .. 2 ( ) 3 ( ).
, , - .
"1" .. , "1" "0" "-1" ( ) , "0" - - , "-1" "0" "1" ( ) .
"11...11" "00...00" - ( ) , "V". "" ( -, "").
, . 1-10:
12 - ( mBnB), 1 2 /2( CMI );
AMI - Alternate Mark Inversion code- RZ "1", PDH;
CMI - Codec Mark Inversion code- NRZ 12 "1" (.. "1" "11",
"00") "0" (.. "0" "01"), PDH SDH;
DB2 - High-Density Bipolar code of order 2 - 2 - RZ "1" ( AMI), "000" "00V "B0V, - "1", , - V- , ;
HDB3 - High-Density Bipolar code ol order 3 - 3 - 1 "1", "0000" "000V" "B00V", - "1", , V , , PDH;
NRZ - Non Return to Zero code - , .. , .
RZ - Return to Zero code - ;
- 12, {00,01,10,11}.
.1 -10. , (): NRZ (), NR2 (), RZ (), ADI (), AMI (e), CMI (), (), () HDB3 ()
(.1-10) , "1" V - , "0" . - NRZ.
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(.1-10) - , "1" +V , "0" - -V . NRZ.
(.1-10) - - RZ, "1" +V /2 , "0" - .
(.1-10) - - RZ. .. (.1-10), - "0" ( ) "1"-o . " RZ c 1 " " RZ-I "( AMI - Alternate Mark Inversion).
" "(CMI) (.1-10). , ( - .1-10, HDB3, PDH (.1-10) SDH, , .1-10). "" " "( ), "1" "0" () 0 180.
.1-10 , , / . RZ NRZ PDH, SDH WDM, - : Ethernet, TR FDDI.
. RZ ( NRZ) - ( RZ) " " . ( 2 f), NRZ ( f).
RZ-AMI , "0" "1" - , - f. , RZ-AMI, - , f /2.
.. ( ) - , . ( ) .
, , - / ( ) ASCII EBCDIC , .. - . .
(), ( - ) ( - ) () - - .
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