Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
1998-07-02
2001-12-25
Vincent, David R. (Department: 2731)
Multiplex communications
Fault recovery
Bypass an inoperative station
C370S228000, C370S248000
Reexamination Certificate
active
06333915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to on-line line monitor systems used for monitoring ATM cross-connect equipments, which perform cross-connecting with respect to ATM cells (where “ATM” is an abbreviation for “Asynchronous Transfer Mode”). Particularly, this invention relates to the on-line line monitor system that performs fault diagnosis with respect to circuit blocks provided for the cross-connecting. This application is based on patent application No. Hei 9-178103 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
The communication networks having redundancy configurations provide presently operating lines (or presently activated lines which are presently placed in an on-line state; hereinafter, simply referred to as operating lines) and spare lines (which are not presently used and are placed in an off-line state or a standby state). When faults occur on the operating lines, the communication networks switch over the operating lines to the spare lines. In an event of occurrence of a large fault in the above communication network, the operating line is subjected to shutoff, so that an input shutoff event occurs. In such an event, the communication network uses the fault as a trigger to switch over line control from the operating line to the spare line.
FIG. 8
shows a conventional example of the on-line line monitor system, which is disclosed by the paper of Japanese Patent Application, Publication No. Hei 4-51723. Herein, there are provided a first line switching equipment
13
and a second line switching equipment
14
, which are connected together by an operating line
11
and a spare line
12
. The second line switching equipment
14
contains a test signal generation circuit
16
and a test signal detection circuit
17
. Herein, the test signal generation circuit
16
sends test signals to a first terminal of the spare line
12
, while the test signal detection circuit
17
receives the test signals returned to a second terminal of the spare line
12
so as to detect a state of the spare line
12
. In addition, the second line switching equipment
14
contains switched connections
18
to
21
. The switched connection
18
is controlled by a first switch (not shown) that performs switching of the line for transmission and reception of the test signals, while the switched connections
19
to
21
are controlled by a third switch (not shown) that performs switchover between the operating line
11
and the spare line
12
.
The first line switching equipment
13
provides a second switch (not shown) that switches over the line used for transmission and reception of the test signals in response to the first switch, as well as a fourth switch (not shown) that switches over line control between the operating line
11
and the spare line
12
. In addition, a loopback circuit
24
having a switched connection
23
is provided for the second switch to turn back the test signals, while the fourth switch has switched connections
25
to
27
.
In the aforementioned on-line line monitor system normally uses the operating line
11
. For this reason, the aforementioned switches establish connections shown in FIG.
8
. That is, the fourth switch of the first line switching equipment
13
establishes connections between the switched connections
25
and
26
, while the third switch of the second line switching equipment
14
establishes connections between the switched connections
19
and
20
. With respect to the spare line
12
, the second switch of the first line switching equipment
13
establishes connections between the switched connections
23
and
27
, while the first switch of the second line switching equipment
14
establishes connections between the switched connections
18
and
21
. Thus, the spare line
12
is placed in a loopback state in the first line switching equipment
13
, so that test signals, which are generated by the test signal generation circuit
16
of the second line switching equipment
14
and are transmitted onto the spare line
12
, are returned back to the test signal detection circuit
17
. The test signal detection circuit
17
examines quality of transmission characteristics of the spare line
12
. In the case of defective, the on-line line monitor system gives warning. In this case, a maintenance man repairs the spare line
12
, so that the spare line
12
can be normally retained in a normal state.
FIG. 9
shows connections that take place when a fault occurs on the operating line
11
so that the on-line line monitor system switches over the operating line
11
to the spare line
12
, wherein parts identical to those of
FIG. 8
are designated by the same reference symbols. As shown in
FIG. 9
, the on-line line monitor system establishes connections between the operating line
11
, the test signal generation circuit
16
and the test signal detection circuit
17
. Thus, the maintenance man is capable of knowing characteristics of the operating line
11
which causes the fault.
FIG. 10
shows another conventional example of the on-line line monitor system, which is disclosed by the paper of Japanese Patent Application, Publication No. Sho 62-279752. This system is applied to the double loop optical communication network, which is configured by double loop circuits (hereinafter, referred to as 0-loop and 1-loop respectively). There are provided a 0-loop light transmission path
40
and a 1-loop light transmission path
41
, which correspond to light loops. A central control unit
31
contains a system control section
32
which is provided for both of the light loops, as well as a central control section
33
for the 0-loop and a central control section
34
for the 1-loop. In addition, the double loop optical communication network of
FIG. 10
contains terminal devices
35
,
36
and
37
, which are arranged along the light loops in connection with the central control unit
31
. So, the central control unit
31
is connected to the terminal devices
35
to
37
by means of the 0-light-transmission path
40
and the 1-light-transmission path
41
. The terminal devices
35
,
36
and
37
contain terminal control sections
43
,
44
and
45
for the 0-loop as well as terminal control sections
46
,
47
and
48
for the 1-loop respectively. The central control section
33
and the terminal control sections
43
to
45
, all of which are provided for the 0-loop, are connected together in loop configuration by means of the 0-loop light transmission path
40
. In addition, the central control section
34
and the terminal control sections
46
to
48
, all of which are provided for the 1-loop, are connected together in loop configuration by means of the 1-loop light transmission path
41
. Transmission direction of the 0-loop light transmission path
40
is reverse to that of the 1-loop light transmission path
41
. The central control unit
31
subjects a prescribed bit pattern of a specific channel to inverse double transmission, so that the central control unit
31
normally sends the bit pattern on the light transmission paths.
FIG. 11
shows an error event that a bit error occurs on a certain light transmission path, wherein parts identical to those of
FIG. 10
are designated by the same reference symbols. In
FIG. 11
, a mark of “X” indicates a fault location
51
, which is placed between the terminal devices
35
and
36
. Either the terminal device
35
or the terminal device
36
detects occurrence of malfunction, which continuously occurs R times or more, with respect to the bit pattern output from the central control device
31
. That is, the terminal control section
44
of the terminal device
36
detects malfunction that occurs on the 0-loop light transmission path
40
, while the terminal control section
46
of the terminal device
35
detects malfunction that occurs on the 1-loop light transmission path
41
. Upon detection of the malfunction, either the terminal device
35
or the terminal device
36
performs loopback operation.
Foley & Lardner
NEC Corparation
Vincent David R.
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