Table A-2. Hdsl Loopback Control Codes - ADTRAN T200 Installation And Maintenance Manual
Encapsulated hdsl range extender
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Upon deactivation of a loopback, the HDSL system
will synchronize automatically. Note that the
synchronization process of the HDSL system upon
deactivation of the HRE loopback could take up to 15
seconds, ensuring all system elements are
synchronized.
Loopback Process Description
In general, the loopback process for the HDSL system
elements is modeled on the corresponding DS1 system
process. Specifically, the HTU-C loopback is similar
to an Intelligent Office Repeater loopback and the
HTU-R loopbacks are similar to an in-line T1
Repeater loopback.
In-band control code sequences are transmitted over
the DS1 link by either the unframed or overwrite
method. The HDSL elements respond to either
method.
The unframed method produces periodic control
sequences and the normal DS1 framing bit is omitted.
The overwrite method produces periodic control
sequences. However, once per frame, the framing bit
overwrites one of the bits in the control sequence.
T
y
e p
S
o
r u
e c
A
b
r b
v e
t a i
d e
(
N
. . )
. . . .
i 3 .
(
N
. . )
. . . .
i 4 .
(
N
. . )
. . . .
i 2 .
(
N
. )
. . . .
i 3 .
C (
. )
. . . .
i 6 .
C (
. )
. . . .
i 5 .
C (
. )
. . . .
i 4 .
C (
. )
. . . .
i 5 .
W
s e
o c
m
(
N
. )
. . . .
F .
(
) C
. . . .
3 . .
(
N
. )
. . . .
F .
(
N
. )
. . . .
F .
(
) C
. . . .
3 . .
(
) C
. . . .
3 . .
(
N
. )
. . . .
F .
(
) C
. . . .
3 . .
(
N
. )
. . . .
i 1 .
(
N
. )
. . . .
F .
(
N
C /
. )
i 1 .
(
N
C /
. )
F .
N
o
e t
: s
T
e h
S
o
r u
e c
o c
u l
m
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o
k r
s
u o
c r
d e
l A
c l
d o
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a
e r
n i
a b
A
l l
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l s
t s i
d e
a
61246041L3-5A
Table A-2. HDSL Loopback Control Codes
7 n
(
1 1
0 1
0 0
) 0
7 n
(
1 1
1 1
0 0
) 0
6 n
1 (
0 1
0 0
) 0
6 n
1 (
1 1
0 0
) 0
7 n
(
1 1
1 1
1 1
) 0
7 n
(
1 1
1 1
0 1
) 0
6 n
1 (
1 1
0 1
) 0
6 n
1 (
1 1
1 1
) 0
F
1
E
F
1
E
F
4 0
F
6 0
F
4 0
F
6 0
F
2 0
F
2 0
6 n
1 (
0 0
0 0
) 0
F
8 4
E (
S
- F
D
) L
3 n
(
0 1
) 0
F
4 2
E (
S
- F
D
) L
n
i
d n
c i
t a
s e
w
i h
h c
i s
e d
o
t f
e h
o c
e d
w
h
e l i
a
C (
i )
d n
c i
t a
s e
a
c
d n
u
l n
s e
l s
b a
l e
d e
E
S
- F
D
L
o b
e v
m
u
t s
e b
s
n e
f t
r o
a
m
i
i n
m
61246041L3-5, Issue 1
The unit can detect the loopback activation or
deactivation code sequence only if an error rate of
-03
1E
or better is present.
DDS Latching Loopback Operation
If the unit is optioned for FT1 mode, then DDS
Latching Loopback operation is supported as
described in Bellcore TA-TSY-000077, Issue 3,
Section 5.1.3. The HTU-C and any HRE units which
are in the HDSL circuit are treated as Identical
Tandem Dataports and the HTU-R is treated as a
Different Tandem Dataport. For a complete
description of the DDS Latching Loopback codes,
refer to Bellcore TA-TSY-000077, Issue 3, Section
5.1.3.
Loopback Control Codes
A summary of control sequences is given in
Table A-2 and Table A-3.
In all control code sequences presented, the
in-band codes are shown left-most bit transmitted
first, and the ESF data link codes with right-most
bit transmitted first.
C
o
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N
a
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p o
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f
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m
L
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p o
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a d
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f
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m
c
s u
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m
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p o
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s u
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m
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p o
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p o
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a d
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p o
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a d
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p o
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NOTE
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w
a
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T
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w
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w
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H
R
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w
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w
a
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c
s u
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m
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H
T
U
. C
r e
o t
w
a
d r
c
s u
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H
T
U
. R
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o t
w
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w
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w
a
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H
T
U
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o t
w
a
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c
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t a
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T
U
. C
o t
w
a
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o
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t a
H
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. 1
o t
w
a
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t a
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R
E
. 2
r e
o t
w
a
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c
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R
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w
a
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. 2
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w
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o
k r
t a
H
T
U
. R
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o t
w
a
d r
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H
T
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R
o t
w
a
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o
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t a
H
T
U
. R
o t
w
a
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o
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t a
H
T
U
. R
s
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f t
o r
. m
F
r o
e
a x
m
p
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t c
d e
a
d n
a
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. R
. C
R
. E
R
. E
H
R
. E
(
N
i )
d n
c i
t a
s e
a
u
o p
. n
A-5
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