Source: http://www.docstoc.com/docs/43327832/Loopback-Test-Starting-System---Patent-5166923
Timestamp: 2014-04-16 05:07:39
Document Index: 442472565

Matched Legal Cases: ['art 611', 'art 613', 'art 611', 'art 613', 'art 611', 'art 615', 'art 612', 'art 611', 'art 612']

Loopback Test Starting System - Patent 5166923
United States Patent: 5166923
5,166,923
A loopback test starting system is provided for starting a loopback test.
The loopback test starting system includes a first loopback controller
which detects a first loopback control signal from a digital data services
network side and generates a first loopback starting signal. In addition,
a second loopback controller is provided which detects a second loopback
control signal from a subscriber side and generates a second loopback
starting signal in response. The loopback test starting system also
includes a first loopback forming device which forms a first loop from the
digital data services network side through the subscriber side and back to
the digital data services network side, and a second loopback forming
device which forms a second loop from the subscriber&#39;s side through the
digital data services side and back to the subscriber side. Further, the
loopback testing starting system includes first and second loopback
detection and resetting devices for resetting and stopping the detection
operations of the first and second loopback controllers. Based on this
above configuration, the loopback test starting system is able to avoid a
loopback closed circuit with out prohibiting a loopback test from the
subscriber&#39;s side, thus improving the quality of the maintenance control
of the entire network.
Ohmori; Hisakazu (Tokyo, JP), Ishii; Yoshinori (Tokyo, JP)
07/574,096
1-224138
370/249  ; 370/420; 370/434; 379/22.01
H04J 3/14&amp;nbsp(20060101); H04J 001/16&amp;nbsp()
370/15,13,13.1,14 375/10 379/5,6,27,102 371/20.5,71
Banzi, Jr. et al.
1.  A loopback test starting system, provided between a digital data services network side and a subscriber side, for executing a loopback test between said digital data
services network side and said subscriber side, comprising:
first loopback controlling means for performing a first detection operation detecting a first loopback control signal from said digital data services network side, and for generating a first loopback starting signal upon detection of said first
loopback control signal;
second loopback controlling means for performing a second detection operation detecting a second loopback control signal from said subscriber side, and for generating a second loopback starting signal upon detection of said second loopback
first loopback detection resetting means for resetting and stopping the second detection operation performed by said second loopback controlling means upon detecting said first loopback control signal by said first loopback controlling means;
2.  A loopback test starting system including a plurality of loopback test starting apparatuses, provided between a digital data services network side and a subscriber side, for executing a loopback test, each of the plurality of loopback test
starting apparatuses comprising:
first loopback controlling means for performing a first detection operation detecting a first loopback control signal from said digital data services network side, and for either activating said first loopback forming means in a present stage or
transmitting the first loopback control signal to one of the plurality of loopback test starting apparatuses connected in a next stage;
second loopback controlling means for performing a second detection operation detecting a second loopback control signal from said subscriber side, and for either activating said second loopback forming means in the present stage or transmitting
the second loopback control signal to the one of the plurality of loopback test starting apparatuses connected in the next stage;
first loopback detection resetting means for resetting and stopping the second detection operation performed by said second loopback controlling means, upon detecting said first loopback control signal by said first loopback controlling means;
3.  A loopback test starting system including a plurality of loopback test starting apparatuses, provided between a digital data services network side and subscriber side for executing a loopback test each of the plurality of loopback test
starting apparatuses, comprising:
first loopback controlling means for performing a first detection operation detecting a first series of different loopback control signals from said digital data services network side, for controlling a first state transition of one of the
plurality of loopback test starting apparatuses in a present stage pursuant to the first series of different loopback control signals, and for either activating said first loopback forming means in the present stage or controlling another of the
plurality of loopback test starting apparatuses connected in a next stage in accordance with said first state transition;
second loopback controlling means for performing a second detection operation detecting a second series of different loopback control signals from said subscriber side, for controlling a second state transition of the one of the plurality of
loopback test starting apparatuses in the present stage pursuant to the second series of different loopback control signals, and for either activating said second loopback forming means in the present stage or controlling the another of the plurality of
loopback test starting apparatuses connected in the next stage in accordance with said second state transition;
first loopback detection resetting means for resetting and stopping the second detection operation performed by said second loopback controlling means, upon detecting one of said first series of different loopback control signals by said first
loopback controlling means;  and
second loopback detection resetting means for resetting and stopping the first detection operation performed by said first loopback controlling means, upon detecting one of said second series of different loopback control signals by said second
loopback controlling means.
4.  The loopback test starting system according to claim 3, wherein:
said first loopback detection resetting means resets and stops the second detection operation performed by said second loopback controlling means, when said first loopback controlling means controls the first state transition such that said first
loopback controlling means does not activate said first loopback forming means in the present stage as instructed by a received one of said first series of different loopback controlling signals from said digital data services network side but transmits
said received one of said first series of different loopback controlling signals having a first current condition to said another of the plurality of loopback test starting apparatuses connected in the next stage;  and
said second loopback detection resetting means resets and stops the first detection operation performed by said first loopback controlling means, when said second loopback controlling means controls the second state transition such that said
second loopback controlling means does not activate said second loopback forming means in the present stage as instructed by a received one of said second series of different loopback control signals from said subscriber side but transmits said received
one of said second series of different loopback control signals having a second current condition to said another of the plurality or loopback test starting apparatuses connected in the next stage.
5.  The loopback test starting system according to claim 4, wherein:
said first loopback controlling means does not activate said first loopback forming means in the present stage upon receiving a predetermined one of said first series of different loopback controlling signals from said digital data services
network side and transmits said predetermined one of said first series of different loopback control signals having a third current condition to the another of the plurality of loopback test starting apparatuses connected in the next stage;  and
said second loopback controlling means does not activate said second loopback forming means in the present stage upon receiving a predetermined one of said second series of different loopback control signals from said subscriber side and
transmits said predetermined one of said second series of different loopback control signals having a fourth current condition to the another of the plurality of loopback test starting apparatuses connected in the next stage.
6.  The loopback test starting system according to claim 4, wherein:
said first loopback controlling means does not transmit a first control code to said another of the plurality of loopback test starting apparatuses connected in the next stage for instructing the another of the plurality of loopback test starting
apparatuses to activate a next state first loopback forming means therein, when said first loopback controlling means controls the first state transition such that said first loopback controlling means activates said first loopback forming means in the
present stage as instructed by the received one of said first series of different loopback control signals from said digital data services network side;  and
said second loopback controlling means does not transmit a second control code to said another of the plurality of loopback test starting apparatuses connected in the next stage for instructing the another of the plurality of loopback test
starting apparatuses to activate a next stage second loopback forming means therein, when said second loopback controlling means controls the second state transition such that said second loopback controlling means activates said second loopback forming
means in the present stage as instructed by the received one of said second series of different loopback controlling signals from said subscriber side.
7.  The loopback test starting system according to claim 3, wherein:
said first loopback controlling means comprises a first state counter changeable to cause the first state transition of said first loopback controlling means;  and
8.  The loopback test starting system according to claim 7, wherein:
said first loopback detection resetting means resets said second state counter in said second loopback controlling means pursuant to the first series of different loopback control signals detected by said first loopback controlling means, thereby
resetting the second detection operation performed by said second loopback controlling means;  and
said second loopback detection resetting means resets said first state counter in said first loopback controlling means pursuant to the second series of different loopback control signals detected by said second loopback controlling means,
thereby resetting the first detection operation performed by said first loopback controlling means.
9.  The loopback test starting system according to claim 7, wherein:
said first loopback controlling means resets said first state counter by receiving a predetermined one of said first series of different loopback control signals from said digital data services network side after making a state transition such
that said first loopback controlling means transmits said first series of different loopback control signals having a first current condition to said another of the plurality of loopback test starting apparatuses connected in the next stage or such that
said first loopback controlling means activates said first loopback forming means in the present stage;  and
said second loopback controlling means resets said second state counter by receiving a predetermined one of said second series of different loopback controlling signals from said subscriber side after making a state transition such that said
second loopback controlling means transmits said second series of different loopback controlling signals having a second current condition to said another of the plurality of loopback test starting apparatuses connected in the next stage or such that
said second loopback controlling means activates said second loopback forming means in the present stage.
10.  The loopback test starting system according to claim 2, wherein:
each of the plurality of loopback test starting apparatuses is installed at a digital signal zero data port at one of a first concentrator rack within a central switching office and an office channel unit data port within a second concentrator
rack in a local switching office.
11.  The loopback test starting system according to claim 10, wherein:
12.  The loopback test starting system according to claim 3, wherein:
said first and second series of different loopback control signals are transmitted in bits on a time divisional multiplex channel.  Description
Recently, DDSNs that serve various digital data like pieces of intercorporate information, voices, images, etc. have become used on a wide scale.  The maintenance control of digital data systems that connects DDSNs and their remote terminals
becomes an important consideration in this situation.
In FIG. 1, a DDSN 111 is connected to digital signal zero data port (DS0-DP) 132 of a central office terminal, (COT) 131.  A data transmission speed of the DDSN 111 is 64 kbps.  The digital signal zero data port 132 is connected to a
multiplexer/demultiplexer (MUX/DMUX) 133.  The multiplexer/demultiplexer 133 of the central office terminal 131 and a multiplexer/demultiplexer circuit 138 of a remote terminal (RT) 137 are connected via a T1 line (primary rate 1.544 Mbps) 135.  The
multiplexer/demultiplexer 138 is connected to an office channel unit data port (OCU-DP) 139.  The office channel unit data port 139 of the remote terminal 137 and a data service unit (DSU) 157 that accommodates a terminal equipment (TE) 155 are connected
via a subscriber&#39;s line 153.  This subscriber&#39;s line 153 serves a subscriber with data transmission speeds of 2.4, 4.8, 9.6 and 56 kbps.
The central office terminal 131 is located a few hundred meters away from the DDSN 111.  The length of the T1 line 135 is a few kilometers.  The length of the subscriber&#39;s line 153 is a few kilometers.  The length of a line that connects the
terminal equipment 155 to the data service unit 157 is a few tens of meters.
The configuration of the central office terminal 131 and the remote terminal 137 is called a digital loop carrier system (hereafter abbreviated as DLC) which is introduced so that the DDSN 111 can accommodate a remotely located subscriber.  The
DLC connects the DDSN and the subscriber with a multiplexed loop (T1 line 135) and transmits data of the DDSN 111 or the subscriber&#39;s line 153 multiplexed in a maximum of 24 channels, so that subscribers are efficiently accommodated.
In FIG. 2, (a) is a data format of the DDSN 111, (b) is a data format of the T1 line 135.  The multiplexers/demultiplexers 133 and 138 multiplex data ((a)) having a data transmission speed of 64 kbps over 24 channels ((b)) and demultiplex data
((b)) having a data transmission speed of 1.544 Mbps into data ((a)) having a data transmission speed of 64 kbps.
In FIG. 3, a lineside loopback detector (hereafter abbreviated as LLD) 311 detects a loopback control code received from the DDSN side and outputs a loopback starting signal if the code matches a predetermined loopback control code.  A lineside
loopback point (hereafter abbreviated as LLP) 313 forms a loopback path by responding to this loopback starting signal.  A dropside loopback detector (hereafter abbreviated as DLD) 315 and a dropside loopback point (hereafter abbreviated as DLP) 317 work
similarly against a loopback control code received from a multiplexer/demultiplexer side (a subscriber side).
In a loopback test from the DDSN side, a path is formed with DLP 317, LLD 311, LLP 313, DLD 315 and DLP 317.  Also, in a loopback test from the demultiplexer side (a subscriber side), a path is formed with LLP 313, DLD 315, DLP 317, LLD 311 and
LLP 313.
Incidentally, the loopback test is controlled by a starting system (latching loopback), where the loopback point that has once formed a loopback path maintains the current condition until the loopback point receives an order to clear the
In FIG. 4, DDSN 410 is connected to DLC 420 equipped with a central office terminal (COT) 131-1 and a remote terminal (RT) 137-1.  DLC 420 is connected to DLC 430 equipped with a central office terminal 131-2 and a remote terminal 137-2 via an
trunk line (64 kbps) 440.  DLC 430 is connected to a data service unit 457 via a subscriber&#39;s loop 453.
When a return path is formed due to a closed-circuit failure of a channel between the central office terminal 131-1 and the remote terminal 137-1, a loopback control code sent from the central office terminal 131-1 is returned without being
received by the remote terminal 137-1 (L2) and is received by the central office terminal 131-1.
The central office terminal 131-1 makes a closed loop within itself, by forming a loopback path from a subscriber side because of a misidentification of this loopback control code as a loopback control code from a subscriber side (L3), and
becomes separated from DDSN 410.  Thus, the DDSN 410 is made unable to clear a loopback.
Besides, if a loopback action that corresponds to a subscriber side is prohibited in advance so that a misidentification of the loopback starting direction described above is avoided, a loopback test from a subscriber side becomes impossible,
which causes a quality deterioration of system maintenance control and makes an installing operation of communication equipment more difficult due to an increase in the number of points which have to be checked at the time of its installation.
Namely, in this invention, more than one unit of loopback test starting equipment is installed between a DDSN side and a subscriber side.  The loopback test starting equipment is installed in digital signal zero data port (DS0-DP) on a central
office terminal rack (COT) or in an office channel unit data port (OCU-DP) in a remote terminal rack(RT).  In addition, a multiple of such paired connections of the central office terminal rack and the remote terminal rack can be tandem connected via a
trunk line.  Each unit of loopback test starting equipment thus installed executes a loopback test by forming a return path to the direction of an input side by a control from the same input side.
Based on the configuration described above, this invention first has loopback forming parts, each of which forms a return path to the DDSN side or to the subscriber side.  These parts are installed at two points, for instance at an output part to
the subscriber side and at an output part to the DDSN side.
Next, this invention has loopback controlling parts including a first loopback controlling part that controls loopback test starting equipment connected to the next stage or starts each loopback forming means within the loopback test starting
equipment depending on the transition between each status (described later), by sequentially detecting various sorts of loopback control signals from the DDSN side or the subscriber side and by transforming itself to correspond to the detected result of
each of the signals.  The first controlling part can transform itself to a status, for example, in which it forwards the received loopback control signals &quot;as is&quot; (in their current condition) to the loopback test starting equipment connected to the next
stage without starting any loopback forming part in its own stage, by receiving a predetermined loopback control signal from the DDSN side or the subscriber side.  Furthermore, the controlling part can control the loopback test starting equipment
connected to the next stage so that it does not send a control code that directs the start of the loopback forming part within the equipment, when, for example, the controlling part transforms itself to a status in which it starts each loopback forming
part in its own stage based on a directive of the above loopback control signal.  To control such a status transition, the controlling part contains a status counter, for example, and transforms its status by changing the counter value.  Incidentally,
said controlling part can set itself to the initial condition by resetting its status counter when it receives a predetermined loopback control signal from the DDSN side or the subscriber side, after said controlling part transforms itself to a status in
which it forwards a received loopback control signal to the loopback test starting equipment connected to the next stage &quot;as is&quot; or to a status in which it starts each loopback forming part in its own stage.  Meanwhile, the loopback control signal is
transmitted using a byte in an interstation data channel, for example.
In addition, this invention has a loopback detecting operation resetting part for resetting the detecting operation of the loopback control signal of the other loopback controlling part and stopping the detecting operation, according to the
detecting result of one loopback controlling part.  When, for instance, one loopback controlling part does not start each loopback forming part in its own stage described before based on the directive of the loopback control signal from the DDSN side or
from the subscriber side and transforms itself to a status in which it forwards the received loopback control signal &quot;as is&quot; to the loopback test starting equipment connected to the next stage, the resetting part resets the detecting action of the other
loopback controlling part&#39;s loopback control signal and stops its detecting action.  In this case, said resetting part executes a resetting action, for example, by resetting the status counter of the other loopback controlling part.
As explained above, in this invention, when, for instance, the loopback controlling part connected to the DDSN side does not start each of the loopback forming parts in its own stage and transforms itself to a status in which it forwards the
received loopback control signal &quot;as is&quot; to the loopback test starting equipment connected to the next stage of the subscriber side, the loopback detection action resetting part stops the detecting action of the loopback control signal from the
subscriber side at the loopback controlling part connected to the subscriber side.
This enables an occurrence such as service shutdown due to forming of a loopback closed circuit to be avoided because the loopback controlling part of the subscriber side of its own stage detects the loopback control signal sent from its own
stage to the subscriber side&#39;s next stage &quot;as is&quot;, when a fault such as a short circuit occurs between its own stage and the next stage, for example.
Those of ordinary skill in the same art as the applicant can easily understand other purposes and characteristics of this invention from the attached drawings and the explanations of the principle and the preferred embodiment of this invention.
FIG. 7 is a block diagram showing the embodiment&#39;s configuration,
The loopback controlling part 611 detects a loopback control signal from the DDSN side and determines whether the loopback control signal forms a return path in loopback forming part 613 or in a later stage.  If the result of the detection
corresponds to the former, the loopback controlling part 611 sends a loopback starting signal to the loopback forming part 613 and forms a return path to the DDSN side.  If the result of the detection corresponds to the latter, the loopback controlling
part 611 passes the loopback control signal and has a later stage process the loopback control signal.
The loopback detecting operation resetting part 615 stops a detecting operation by resetting the detecting operation of the loopback controlling part 612 that detects a loopback control signal from the subscriber side, in either case of reaching
a loopback starting status.  Consequently, even if the loopback control signal that passes the loopback controlling part 611 for a loopback control in a later stage is input into the loopback controlling part 612 on the opposite side by a forced return,
since the detecting operation of the loopback control signal has already stopped, a loopback starting to the subscriber side by an error is prevented.
In digital signal zero data port (DS0-DP) 720A loaded on a concentrator rack on the central office terminal (COT), a loopback control code from the DDSN side is sent to a demultiplexing circuit side via DLP 721A, LLD 723A and LLP 725A.  LLD 723A
forms a loopback path by outputting a loopback starting signal to LLP 725A when LLD 723A detects a predetermined loopback control code.  The loopback control code from the subscriber side input via the multiplexing/demultiplexing circuit (MUX/DMUX) is
sent to the DDSN side via LLP 725A, DLD 727A and DLP 721A.
The output of status counter 728A of LLD 723A is input to status detector 729A.  Status detector 729A, which detects the output of status counter 728A showing a predetermined value, sends a clear signal to the clear terminal (CLR) of status
counter 730A of DLD 727A.
In digital signal zero data port (DS0-DP) 720B loaded on the remote terminal (RT) concentrator rack at a tandem connection time, LLP 725B, DLD 727B, DLP 721B and LLD 723B are connected symmetrically to the multiplex isolation circuit and digital
signal zero data port 720A of the central office terminal (COT) rack.
The loopback control code from the DDSN side input by the demultiplexing circuit is sent to the subscriber side via LLP 725B, DLD 727B and DLP 721B.  The loopback control code input from the subscriber side is sent to the demultiplexing circuit
side via DLP 721B, LLD 723B and LLP 725B.
In status 1, a detection of thirty [30] consecutive bytes of LBE code that makes LLD 723A ready for a loopback starting triggers a setting of status counter 728A to status 2, and LBE codes received thereafter are converted to MAP (Mapping) codes
In status 2, another detection of thirty [30] consecutive bytes of LBE code triggers a setting of status counter 728A to status 3 ready for FEV (For End Voice) code.  This LBE code is received as MAP code in DLD 727B of the next stage and DLD
727B does not transform its own status.
(5) When LLD 723A becomes status 3, DDSN sends data &quot;1&quot; for starting DLP 721B&#39;s loopback without executing LLP 725A&#39;s loopback.
After detecting thirty [30] consecutive bytes of data &quot;1&quot;, LLD 723A stops converting LBE code to MAP code and outputting MAP code and sets status counter 728A to status 4.  Thereafter, LLD 723A maintains status 4 and ignores anything but TIP
code, and sends it to digital signal zero data port 720B set in the remote terminal (RT) rack side.
When the loopback control code sent from digital signal zero data port 720A is returned on, its way before reaching digital signal zero data port 720A set in a concentrator rack on the remote terminal side concentrator (RT) rack side in the above
loopback start, the same control operation as that to DLD 727B is made to DLD 727A.
However, after data &quot;1&quot; in procedure (5), status counter 730A of DLD 727A shows status 0 and is not transformed to the status in which the returning input of the loopback control code forms a loopback path.
Namely, in the prior art, DS0-DP could not receive the TIP code due to a separation from DDSN 720A, because DLD 727A formed a loopback path within DLP 721A by making operations of procedures (1) through (8) that were supposed to be done by DLD
727B.  However, according to the embodiment of this invention, when DDSN side status counter 728A becomes status 4 and comes to know of not being a loopback point, it sets other status counter 730A to status 0, and DLD 727A&#39;s status transition is
stopped, even if the returning loopback code is received.  Thus, an erroneous loopback action can be avoided.
Loopback test starting system, Ohmori, et al., Hisakazu Ohmori, Yoshinori Ishii, Application number 07 574-096, Multiplex Communications, Telephonic Communications, loopback test, patent search, patent attorney, Page Range, English Español, Patent Inventor, Patent Community, wherein said, control signal, SIGNAL PROCESSING
1. Field of the InventionThis invention relates to a system for starting a loopback test, which an input side controls by forming a loop path in a terminating equipment set between digital data system network (hereafter abbreviated as DDSN) side and a subscriber side.2. Description of the Related ArtRecently, DDSNs that serve various digital data like pieces of intercorporate information, voices, images, etc. have become used on a wide scale. The maintenance control of digital data systems that connects DDSNs and their remote terminalsbecomes an important consideration in this situation.FIG. 1 shows a configuration of the whole digital data system.In FIG. 1, a DDSN 111 is connected to digital signal zero data port (DS0-DP) 132 of a central office terminal, (COT) 131. A data transmission speed of the DDSN 111 is 64 kbps. The digital signal zero data port 132 is connected to amultiplexer/demultiplexer (MUX/DMUX) 133. The multiplexer/demultiplexer 133 of the central office terminal 131 and a multiplexer/demultiplexer circuit 138 of a remote terminal (RT) 137 are connected via a T1 line (primary rate 1.544 Mbps) 135. Themultiplexer/demultiplexer 138 is connected to an office channel unit data port (OCU-DP) 139. The office channel unit data port 139 of the remote terminal 137 and a data service unit (DSU) 157 that accommodates a terminal equipment (TE) 155 are connectedvia a subscriber's line 153. This subscriber's line 153 serves a subscriber with data transmission speeds of 2.4, 4.8, 9.6 and 56 kbps.The central office terminal 131 is located a few hundred meters away from the DDSN 111. The length of the T1 line 135 is a few kilometers. The length of the subscriber's line 153 is a few kilometers. The length of a line that connects theterminal equipment 155 to the data service unit 157 is a few tens of meters.The configuration of the central office terminal 131 and the remote terminal 137 is called a digital loop carrier system (hereafter abbreviated as DLC)
Digital Point-to-Point System Loopback Testing
atm-loopback