-
110000
55..
55..11..
. - , , (, ) - () - . , , - () . - : , , , , , .
( ) () "0" "1", . , , , . , -:
) -,
) ,
) () - ,
) ().
5.1 - ) - ) .
-
110011
:
,
.
, . .
5.1
, , , ,
( -, ) -
, FET , , MNOS, , (CRT)
, , , : - ; MNOS - --; FET - ; - -
55..22..
. , , , -, . :
-
110022
, - , . - 80- , , . - 80 ( 80 ).
12 () X,Y,0,...,9. 0 9 , X,Y,0 ( 0 -) . , . . 0-9 , , , , . - .
80- 96- , .
- . - . - (. 5.1).
5- 8- . 5- CCITT No. 1, - ISO 7 (ASCII, CCITT Alfabet No. 2).
.
, , () . () -
-
110033
- . - , :
) ;
) ;
) .
)
, , ( ), . - . -, .
- ( . off-line ), .
)
( ). - . : E-13B, , CMC-7 (CMC - Code for Magnetic Characters) -
) . -
1 2 3 4 5 6 7 8
5.1
-
110044
. .
-. - .
)
, . - OCR-A OCR-B (OCR - Optical Character Recognition - ). -, ,
.
( , . bar code) () . , .
- EAN ( European Article Number - ) : EAN-13 () , EAN-8, UPC
(UPC Universal Product Code ) aa UPC-A UPC-D 14 32 . UPC-E UPC-A ,
- .
-
110055
55..33..
- . - , :
,
,
,
,
( , ),
(),
,
( ),
(, .).
55..44..
- . :
,
,
.
. - ( . ).
() - , . .
-
110066
:
) ,
) ,
) .
:
(),
,
,
.
:
1)
2) ( ).
, . -. . COM (COM - Computer Output to MIcrofilm/Microfiche - -
/).
55..55..
-. () (. ) - () .
- . BH (. 5.2), B , () , H - . , -
-
110077
, "" BH . , - , .
- ( ) : ( ), , ( . )
- :
1) ( 400 bit/mm) ,
2) ( 7 - 15 ms ),
3) (10 , 30 ),
4) ,
5) ( 1 MB - GB ).
)
5.2
+Mr -Mr
M
+Mr
-Mr
)
) BN
B
H
"1"
"0"
i s
)
s
t
x
-
110088
. 5.2 . - . . 5.2 . 5.2 () .
- . 5.2. - - . , , - . s(t) - .
- . . () . () . .
55..66..
( - ). , 0,1 mm . - , , (-) () .
. - .
-
110099
12,7 mm (1/2 ), 700 - 750 . 30 250 MB. 1 - 2 m/s, 5 - 7 m/s.
: 32 bit/mm (800 bpi - ), 63 bita/mm (1600 bpi), 246 bit/mm
(6250 bpi). 7 9 ().
. 5.3 . - . (MBR), . - 5 - 10 ms, 15 - 20 mm. 300 KB/s 1
MB/s.
. . GB.
)
5.3
) )
_1 _2 MBR
MBR MBR MBRMBR
-
111100
10 - 30 ms, 10 ms.
.5.3 . - , , , . :
) (), . ,
) , . .
-. , /. , - () .
, , 2 - 10 ms.
- . - .
( ) . , "0" 1.
CD ROM ( . CD ROM Compact Disk Read-Only Memory -) -
-
111111
- , , , - , , . - : , . .
. 120 , 20000, 1,6 . 100 (1010 bit/cm 108 bit/cm). 25000 bpi
(984 bita/mm). 550 MB. - , , 200 o/min 500 o/min.
. . . - . . - . - . .
55..77..
- . -, , . - -. - () -. :
-
111122
) ,
) "0" "-" .
- . . , () , -. , - () . , . () . - "1" "0", .
RRZZ
. RZ (. RZ Return to Zero ), . 5.4. , "0" () Mr "1" +Mr - . - ()
. - .
RZ , "0" "1" . - , "0" - , "1" - . () - , "1" , . () . - "0" ""
() ,
-
111133
. , ("") , . - . - -, .
RRBB
Mr (). "1" +Mr, "0" -Mr. - RB (. RB Return to Bias -), .
5.4.
NNRRZZ
- - NRZ (. NRZ Non Return to Zero - ), . 5.4. "0" () Mr "1" +Mr.
-
0+
-0
0 0
+
+ +
-
- -
0 01 1 01 0 01 1 01
0 01 1 01 0 01 1 01
) (RZ)
) (RB)
) (NRZ)
)
1 (NRZI)
5.4 RZ, RB, NRZ i NRZI
-
111144
"0" "1" . , "1" "0" "0" "1"
, . - "0" 1. . "0" "1" "0", , "1". "1" "0" ( ), "1" - .
- . . , . - -.
NNRRZZII
NRZ - . NRZ "0" "1" - . NRZI (. NRZI Non Return to Zero Inverted
) , . 5.4. - "1" . Mr +Mr "1" , - "0" "1". - "1" , "0" "1". , , - .
- ( ).
NRZI NRZ . - . -
-
111155
. -, NRZI "1". - , . , . NRZI "0" , - .
, NRZ NRZI, RZ . - . -, . , - - . . . .
PPEE
PE (. PE Phase Encoding -), PM (. PM Phase Modulation ) (.
5.5).
"0" - . "1" . - : "1" - "0" . - . - . , , NRZI. - .
-
111166
FFMM ((DDFF))
( ) - DF (. DF Double Frequency ) FM (. FM Frequency Modulation
), (. 5.5).
, NRZI , -. "1" NRZI , "1", . NRZI . "" . () . , -. -. , NRZI
.
NRZI -, . , . . :
MFM ,
GCR ,
RLL .
0+
-
0 01 1 01
0+
-
0 01 1 01
)
(PE) -
)
(FM)
5.5 PE FM
-
111177
MMFFMM
"1" DF PM - NRZI -. -, NRZI DF PM. , - , DF PM . , - NRZI . , -
- .
- . (, ) - (. ) - X0. - - - X0 (. ). . . FM "1" , "0". FM . MFM
M2FM.
. 5.6 FM . X0. - "0", - . 5.6. - X - X0 , 2X0. , . 5.6, X0. , .
MFM
-
111188
(. MFM Modified Frequency Modulation -).
, . X0, 1.5X0, - 0.5X0. 1.5X0 "1" "0", . 2, 1,5 .
MFM - , M2FM, MFM, .
GGCCRR
GCR (. GCR Group Coded Recording -) - 6250 (246 bit/mm). - , .
NRZI - . : . 5 4 .
5.6 MFM FM
)
FM ) MFM
)
0+
-
0 10 1 10 0 0
0+
-
0 10 1 10 0 0
-
111199
5.2 GCR
0 0000 11001 4 0100 11101 8 1000 11010 C 1100 11110 1 0001 11011
5 0101 10101 9 1001 01001 D 1101 01101 2 0010 10010 6 0110 10110 A
1010 01010 E 1110 01110 3 0011 10011 7 0111 10111 B 1011 01011 F
1111 01111
RRLLLL
X0 . X0, . - RLL (. RLL Run Length Limited ). "1" (. X0) . .
DF MFM -. , RLL, MFM "1" . (. ) . 5.6 . - "1". RLL -. , - ()
"1",
RLL(d,k), d z k. MFM d = 1 k = 3, . MFM = RLL(1,3).
X0, 0.5X0. - .
-
112200
. RLL - . - . - RLL - . d z k, . z - "1" . X0 . , . .
