Kenwood DP-1100 B Service Manual page 19

D P - 1 1 0 0 B II
(2) T h e principle of d o u b l e erasure c o r r e c t i o n is described
b e l o w . In this c a s e , t h e l o c a t i o n of error is indicated w i t h
a pointer. It is here k n o w n t h a t t w o w o r d s in bill (c) are
w r o n g a n d t h e r e are n o other w r o n g w o r d s .
Using e q u a t i o n (1) in p a r a g r a p h ( 1 ) ,
S = A + B + C + D - P + E
1
0
S u p p o s i n g E = 0, E
A
S = E ,+ E = 2 0 0
1 J C
F r o m Equation (2) of (1
S = 4 A + 3 B + 2C + D + (4E
2
0
S = 3 E + 2 E = 5 0 0
2 J J C
D e t e r m i n i n g E a n d E
B
(3) a n d ( 4 ) ,
2 2
II. FUNDAMENTALS
+ E + E + E - E = 2 0 0
y l f l c D P
= 0 a n d E = 0
D P
+ 3 E + 2 E + E - E ) = 5 0 0
/ 4 B c B Q
f r o m s i m u l t a n e o u s e q u a t i o n s of
c
A' ¥
B' ¥
C
D' ¥
P' ¥ 1,000
Q' ¥ 2,000
(3)
E = 1 0 0
c
5 = A' + B * + C * + D ' - P ' = 200
1
5 = 4A' + 3B' + 2C* + D' — Q' = 500
2
Where
B* = E + E
(4)
T h i s t h e o r y is t h e principle of a Reed S o l o m o n C o d e . In
p r a c t i c e , t h e Reed S o l o m o n Code w i t h f o u r parity w o r d s
is u s e d .
E B = 1 0 0
Bill (c)
100
300
400 Pointer
¥
400
C * + = C + E
B C