CA2102867C - Switch bypass for a public safety calling system - Google Patents
Switch bypass for a public safety calling systemInfo
- Publication number
- CA2102867C CA2102867C CA002102867A CA2102867A CA2102867C CA 2102867 C CA2102867 C CA 2102867C CA 002102867 A CA002102867 A CA 002102867A CA 2102867 A CA2102867 A CA 2102867A CA 2102867 C CA2102867 C CA 2102867C
- Authority
- CA
- Canada
- Prior art keywords
- switch
- switch means
- scx
- routing
- bypass
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q3/00—Selecting arrangements
- H04Q3/0016—Arrangements providing connection between exchanges
Abstract
A switch bypass (10) for a Public Safety Calling System (12) having a first switch A for routing telephone calls, a second switch B for routing telephone calls, and a device 14a and 14b for bypassing the first switch A responsive to a failure in the first switch, and for transferring the cell to the second switch.
Description
R~CKGROUND OF T~ T~V~NTTON
The present invention relates to switch bypasses for a Public Safety Calling System (PSCS).
s In the past, switches, such as Specialized Communication Exchange (SCX) switches, have been used for routing calls in a telephone system. More recently, a 911 emergency service has been added to such telephone systems, termed a Public Safety Calling System (PSCS).
The 911 telephone switches serve to route emergency calls to such locations as a police office or fire station for prompt action.
It has been found, however, that occasionally an SCX of such an emergency 911 telephone system may fail, thus posing the possibility that such emergency calls may not be routed until the SCX has been restored to proper operation condition, which might result in a disaster. It is thus apparent that it would be desirable to still route such emergency 911 calls in the event of a switch failure.
SU~MARY OF T~ T~V~NTTON
A principle feature of the present invention is the provision of a switch bypass for a Public Safety Calling System (PSCS).
The switch bypass of the present invention comprises, first switch means for routing telephone calls, and second switch means for routing telephone calls.
A feature of the invention is that the switch bypass bypasses the first switch means responsive to a failure in the first switch means.
s Yet another feature of the invention is that the switch bypass transfers the calls placed to the first switch means on the second switch means for handling.
Another feature of the invention is that the second switch means properly routes the calls originally placed to the defective first switch means.
Still another feature of the invention is that the first switch means is bypassed through use of at least one cross connect in the first switch means.
Yet another feature of the invention is that the second switch means transfers calls originally placed to the first switch means back to a cross connect of the first switch means for handling.
Another feature of the invention is that the first switch means again properly routes the calls responsive to renewed proper operation of the first switch means.
Thus, a feature of the invention is that the switch bypass minimizes the possibility that an emergency call will not be routed by the defective first switch means.
Another feature of the invention is that the switch bypass provides improved switching capabilities in a more efficient manner.
s Yet another feature of the invention is that the second switch means may be bypassed in the event of failure of the second switch means, and the calls originally placed to the defective second switch means may be transferred to the first switch means for handling.
Thus, a feature of the invention is that both the first and second switch means provide a backup capability of the switch means to prevent loss of emergency telephone calls.
Further features will become more fully apparent in the following description of the embodiments of this invention, and from the appended claims.
n~cRTpTToN OF T~ DRAWTNGS
In the drawings:
Fig. 1 is a block diagram of a switch bypass of the present invention under a condition with a fault in a first switch;
Fig. 2 is a block diagram of the switch bypass of Fig. 1 under a condition with a fault in a second switch; and Fig. 3 is a block diagram of the switch bypass showing different configurations of switches in a switch bypass.
DF.. C:CRTPTTON OF T~F. PRFFFRRFn li~MRoDTM~JTs Referring now to Fig. 1, there is shown a switch bypass generally designated lO for a Public Safety Calling System (PSCS) 12 for routing of emergency 911 telephone calls. As shown, the switch bypass 10 has a first switch A for routing a first set of telephone calls, such as a Specialized Communication Exchange (SCX) switch. The PSCS 12 also has a second switch B
for routing a second set of telephone calls, such as a second Specialized Communication Exchange (SCX) switch.
In usual operation, both the SCX A and SCX B each route different sets of 911 telephone calls dependent upon various relative factors, such as determined by the location of the two switches SCX A and SCX B.
As shown, the first switch SCX A has a plurality of cross connects 14a, 14b, and 14c for a purpose which will be discussed below. The first switch SCX A also has a routing table A 24 for the purpose of routing calls originally placed to the first switch SCX
A, and a back up routing table B 28 for routing telephone calls originally placed to the second switch SCX B. The second switch SCX B also has a routing table B 26 for routing calls originally placed to the second switch SCX B, and a second back up routing table A 30 for routing calls originally placed to the first switch SCX A.
. In the event of a fault in the first switch SCX A, as determined by the user, a command is issued to the first switch SCX A indicating the failure in the switch. Also, the user issues a command up to a digital S cross connect DXCA( see Figure 3) associated with the first switch SCX A. The DXCA usually routes calls on a first branch as indicated by solid lines, and has a switch actuated by the command to route calls on a second different branch by the DXCA, as indicated by the dotted lines in the drawing. In turn, the cross connects 14a and 14b route the incoming call placed from a telephone 16 on a line 18 to the second switch SCX B
which is in a proper operation condition. The second switch SCX B reroutes this call to the cross connect 14c of the first switch SCX A on a line 20 which then routes the call to the receiving telephone 22, such as a police or fire station, in order to complete the emergency call. When the first switch SCX A has been restored to proper operating order, as determined and indicated by the user to the first switch SCX A, the digital cross connect DXCA is restored to its original switch configuration, and the first switch SCX A again will route the incoming 911 telephone calls in the usual manner.
With reference to Fig. 3, when the first switch SCX A is in proper operating order, an incoming call placed by the telephone 16 passes through a Central Office EO 1 to a digital cross connect (DXC)A which routes the call in this switch on the usual solid line 36 to a port El in the first switch SCX A. The first switch SCX A utilizes the routing tables A in the first switch SCX A to route the call on a port Pl and onto line 38 to the DXCA in the usual switching configuration shown by the solid line in the DXC A. In turn, the DXC A routes the call to the primary receiving telephone 22, such as as a police station to monitor the emergency 911 call.
s In the event of a failure in the first switch SCX A, a command is issued by the user to the DXC A in order to actuate this switch to route calls on alternate lines which are shown as dotted lines in the drawing.
lo Thus, an incoming call from the telephone 16 is routed by the DXC A 34 on the alternate line 42 and over a line 44 to a port El of the second switch SCX B. When the failure in the first switch SCX A has been detected, a command is also issued by the user to the second switch SCX B to alert this switch that calls originally placed to the first switch SCX A will be received on the port El. Thus, the command enables the port El in the second switch SCX B which is otherwise rarely used.
The second switch SCX B then utilizes the routing tables A in the second switch SCX B to route the calls onto an alternate port Pl and onto a line 46 to an alternate line 48 of the first DXC A. The DXC A
switches the line 48 to the primary receiver comprising the telephone 22 at the police station in order to complete the call. In this manner, the digital cross connects and first and second switches SCX A and SCX B
cooperate in order to continuously route telephone calls even when the first switch SCX A has failed.
Thus, in accordance with the present invention, the switch bypass 10 overflows emergency telephone calls from the first inoperative switch SCX A
to the second switch SCX B for handling in order to prevent the loss of the emergency calls. The second switch SCX B returns the calls originally placed to the first switch SCX A for completion of the calls.
s With reference to Fig. 2, the second switch SCX B may also have a plurality of cross connects 114a, 114b and 114c, and the routing tables A and B. In the event of a failure of the second switch SCX B while the first switch SCX A is in proper operating order, the calls are transferred by the cross connects 114a and 114b on a line 118 to the first switch SCX A, after which the first switch SCX A routes the calls back to the second switch SCX B on the line 120 in order to route the calls placed by a telephone 116 to the receiving telephone 122, such as the police or fire station associated with the second switch SCX B. In this manner, the first switch SCX A also serves as a backup for the second switch SCX B when the second switch SCX B is not in proper operating order in order to insure the completion of emergency calls originally placed to the second switch SCX B.
The foregoing detailed description has been given for purpose of underst~n~;ng only, and no unnecessary limitations should be understood therefrom, as a modifications will be obvious to those skilled in the art.
The present invention relates to switch bypasses for a Public Safety Calling System (PSCS).
s In the past, switches, such as Specialized Communication Exchange (SCX) switches, have been used for routing calls in a telephone system. More recently, a 911 emergency service has been added to such telephone systems, termed a Public Safety Calling System (PSCS).
The 911 telephone switches serve to route emergency calls to such locations as a police office or fire station for prompt action.
It has been found, however, that occasionally an SCX of such an emergency 911 telephone system may fail, thus posing the possibility that such emergency calls may not be routed until the SCX has been restored to proper operation condition, which might result in a disaster. It is thus apparent that it would be desirable to still route such emergency 911 calls in the event of a switch failure.
SU~MARY OF T~ T~V~NTTON
A principle feature of the present invention is the provision of a switch bypass for a Public Safety Calling System (PSCS).
The switch bypass of the present invention comprises, first switch means for routing telephone calls, and second switch means for routing telephone calls.
A feature of the invention is that the switch bypass bypasses the first switch means responsive to a failure in the first switch means.
s Yet another feature of the invention is that the switch bypass transfers the calls placed to the first switch means on the second switch means for handling.
Another feature of the invention is that the second switch means properly routes the calls originally placed to the defective first switch means.
Still another feature of the invention is that the first switch means is bypassed through use of at least one cross connect in the first switch means.
Yet another feature of the invention is that the second switch means transfers calls originally placed to the first switch means back to a cross connect of the first switch means for handling.
Another feature of the invention is that the first switch means again properly routes the calls responsive to renewed proper operation of the first switch means.
Thus, a feature of the invention is that the switch bypass minimizes the possibility that an emergency call will not be routed by the defective first switch means.
Another feature of the invention is that the switch bypass provides improved switching capabilities in a more efficient manner.
s Yet another feature of the invention is that the second switch means may be bypassed in the event of failure of the second switch means, and the calls originally placed to the defective second switch means may be transferred to the first switch means for handling.
Thus, a feature of the invention is that both the first and second switch means provide a backup capability of the switch means to prevent loss of emergency telephone calls.
Further features will become more fully apparent in the following description of the embodiments of this invention, and from the appended claims.
n~cRTpTToN OF T~ DRAWTNGS
In the drawings:
Fig. 1 is a block diagram of a switch bypass of the present invention under a condition with a fault in a first switch;
Fig. 2 is a block diagram of the switch bypass of Fig. 1 under a condition with a fault in a second switch; and Fig. 3 is a block diagram of the switch bypass showing different configurations of switches in a switch bypass.
DF.. C:CRTPTTON OF T~F. PRFFFRRFn li~MRoDTM~JTs Referring now to Fig. 1, there is shown a switch bypass generally designated lO for a Public Safety Calling System (PSCS) 12 for routing of emergency 911 telephone calls. As shown, the switch bypass 10 has a first switch A for routing a first set of telephone calls, such as a Specialized Communication Exchange (SCX) switch. The PSCS 12 also has a second switch B
for routing a second set of telephone calls, such as a second Specialized Communication Exchange (SCX) switch.
In usual operation, both the SCX A and SCX B each route different sets of 911 telephone calls dependent upon various relative factors, such as determined by the location of the two switches SCX A and SCX B.
As shown, the first switch SCX A has a plurality of cross connects 14a, 14b, and 14c for a purpose which will be discussed below. The first switch SCX A also has a routing table A 24 for the purpose of routing calls originally placed to the first switch SCX
A, and a back up routing table B 28 for routing telephone calls originally placed to the second switch SCX B. The second switch SCX B also has a routing table B 26 for routing calls originally placed to the second switch SCX B, and a second back up routing table A 30 for routing calls originally placed to the first switch SCX A.
. In the event of a fault in the first switch SCX A, as determined by the user, a command is issued to the first switch SCX A indicating the failure in the switch. Also, the user issues a command up to a digital S cross connect DXCA( see Figure 3) associated with the first switch SCX A. The DXCA usually routes calls on a first branch as indicated by solid lines, and has a switch actuated by the command to route calls on a second different branch by the DXCA, as indicated by the dotted lines in the drawing. In turn, the cross connects 14a and 14b route the incoming call placed from a telephone 16 on a line 18 to the second switch SCX B
which is in a proper operation condition. The second switch SCX B reroutes this call to the cross connect 14c of the first switch SCX A on a line 20 which then routes the call to the receiving telephone 22, such as a police or fire station, in order to complete the emergency call. When the first switch SCX A has been restored to proper operating order, as determined and indicated by the user to the first switch SCX A, the digital cross connect DXCA is restored to its original switch configuration, and the first switch SCX A again will route the incoming 911 telephone calls in the usual manner.
With reference to Fig. 3, when the first switch SCX A is in proper operating order, an incoming call placed by the telephone 16 passes through a Central Office EO 1 to a digital cross connect (DXC)A which routes the call in this switch on the usual solid line 36 to a port El in the first switch SCX A. The first switch SCX A utilizes the routing tables A in the first switch SCX A to route the call on a port Pl and onto line 38 to the DXCA in the usual switching configuration shown by the solid line in the DXC A. In turn, the DXC A routes the call to the primary receiving telephone 22, such as as a police station to monitor the emergency 911 call.
s In the event of a failure in the first switch SCX A, a command is issued by the user to the DXC A in order to actuate this switch to route calls on alternate lines which are shown as dotted lines in the drawing.
lo Thus, an incoming call from the telephone 16 is routed by the DXC A 34 on the alternate line 42 and over a line 44 to a port El of the second switch SCX B. When the failure in the first switch SCX A has been detected, a command is also issued by the user to the second switch SCX B to alert this switch that calls originally placed to the first switch SCX A will be received on the port El. Thus, the command enables the port El in the second switch SCX B which is otherwise rarely used.
The second switch SCX B then utilizes the routing tables A in the second switch SCX B to route the calls onto an alternate port Pl and onto a line 46 to an alternate line 48 of the first DXC A. The DXC A
switches the line 48 to the primary receiver comprising the telephone 22 at the police station in order to complete the call. In this manner, the digital cross connects and first and second switches SCX A and SCX B
cooperate in order to continuously route telephone calls even when the first switch SCX A has failed.
Thus, in accordance with the present invention, the switch bypass 10 overflows emergency telephone calls from the first inoperative switch SCX A
to the second switch SCX B for handling in order to prevent the loss of the emergency calls. The second switch SCX B returns the calls originally placed to the first switch SCX A for completion of the calls.
s With reference to Fig. 2, the second switch SCX B may also have a plurality of cross connects 114a, 114b and 114c, and the routing tables A and B. In the event of a failure of the second switch SCX B while the first switch SCX A is in proper operating order, the calls are transferred by the cross connects 114a and 114b on a line 118 to the first switch SCX A, after which the first switch SCX A routes the calls back to the second switch SCX B on the line 120 in order to route the calls placed by a telephone 116 to the receiving telephone 122, such as the police or fire station associated with the second switch SCX B. In this manner, the first switch SCX A also serves as a backup for the second switch SCX B when the second switch SCX B is not in proper operating order in order to insure the completion of emergency calls originally placed to the second switch SCX B.
The foregoing detailed description has been given for purpose of underst~n~;ng only, and no unnecessary limitations should be understood therefrom, as a modifications will be obvious to those skilled in the art.
Claims (10)
1. A switch bypass for a public safety calling system, comprising:
first switch means for routing telephone calls and having a plurality of cross connects for bypassing the first switch means responsive to a failure in the first switch means; and second switch means for routing telephone calls and receiving the call from the first switch means, and for routing the call back to a cross connect of the first switch means.
first switch means for routing telephone calls and having a plurality of cross connects for bypassing the first switch means responsive to a failure in the first switch means; and second switch means for routing telephone calls and receiving the call from the first switch means, and for routing the call back to a cross connect of the first switch means.
2. A switch bypass for a public safety calling system, comprising:
first switch means for routing telephone calls;
a digital cross connect associated with the first switch means;
second switch means for routing telephone calls;
means for bypassing the first switch means responsive to a failure in the first switch means, and for transferring the call to the second switch means;
and means for routing the call from the second switch means through the digital cross connect associated with the first switch means during failure of the first switch means to the desired receiving party.
first switch means for routing telephone calls;
a digital cross connect associated with the first switch means;
second switch means for routing telephone calls;
means for bypassing the first switch means responsive to a failure in the first switch means, and for transferring the call to the second switch means;
and means for routing the call from the second switch means through the digital cross connect associated with the first switch means during failure of the first switch means to the desired receiving party.
3. The switch bypass of claim 2 wherein the transferring means includes a cross connect in the first switch means.
4. The switch bypass of claim 2 wherein the bypassing means includes at least one cross connect in the first switch means.
5. A switch bypass for a public safety calling system, comprising:
first switch means for routing telephone calls and having means for bypassing the first switch means responsive to a fault in the first switch means;
a digital cross connect associated with the first switch means; and second switch means for routing telephone calls and having means for receiving the call from the first switch means and for routing the call back to the digital cross connect of the first switch means during a failure of the first switch means.
first switch means for routing telephone calls and having means for bypassing the first switch means responsive to a fault in the first switch means;
a digital cross connect associated with the first switch means; and second switch means for routing telephone calls and having means for receiving the call from the first switch means and for routing the call back to the digital cross connect of the first switch means during a failure of the first switch means.
6. The switch bypass of claim 5 wherein the bypassing means includes at least one cross connect in the first switch means.
7. The switch bypass of claim 5 wherein the second switch routing means includes at least one cross connect in the first switch means.
8. A switch bypass for a public safety calling system, comprising:
first switch means for routing telephone calls;
a digital cross connect associated with the first switch means;
second switch means for routing telephone calls; and means for overflowing a call placed to the first switch means to the second switch means responsive to a failure in the first switch means, and for routing the call back to the digital cross connect of the first switch means during failure of the first switch means.
first switch means for routing telephone calls;
a digital cross connect associated with the first switch means;
second switch means for routing telephone calls; and means for overflowing a call placed to the first switch means to the second switch means responsive to a failure in the first switch means, and for routing the call back to the digital cross connect of the first switch means during failure of the first switch means.
9. The switch bypass of claim 8 including means for restoring the routing of calls by the first switch means responsive to renewed operation of the first switch means.
10. The switch bypass of claim 9 wherein the second switch means includes means for bypassing a call placed to the second switch means to the first switch means responsive to a fault in the second switch means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US975,243 | 1992-11-11 | ||
| US07/975,243 US5454025A (en) | 1992-11-12 | 1992-11-12 | Switch bypass for a public safety calling system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2102867A1 CA2102867A1 (en) | 1994-05-12 |
| CA2102867C true CA2102867C (en) | 1998-12-29 |
Family
ID=25522823
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002102867A Expired - Fee Related CA2102867C (en) | 1992-11-11 | 1993-11-10 | Switch bypass for a public safety calling system |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5454025A (en) |
| CA (1) | CA2102867C (en) |
| GB (1) | GB2273852B (en) |
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| US5661779A (en) * | 1994-03-07 | 1997-08-26 | Proctor & Associates Company, Inc. | Rapid response backup system for telecommunications networks |
| US6181929B1 (en) * | 1996-05-20 | 2001-01-30 | Motorola, Inc. | Method for switching cell site controllers |
| FI103371B1 (en) * | 1996-06-13 | 1999-06-15 | Nokia Telecommunications Oy | Procedure and system for securing emergency traffic |
| US5862201A (en) * | 1996-09-12 | 1999-01-19 | Simplex Time Recorder Company | Redundant alarm monitoring system |
| FI964968A (en) * | 1996-12-11 | 1998-06-12 | Nokia Telecommunications Oy | Procedure and system for connection of emergency calls in error situations in a telephone network |
| US5912963A (en) * | 1997-03-03 | 1999-06-15 | At&T Corp. | Method and apparatus for providing an alternate telecommunications network |
| JPH1173898A (en) | 1997-08-28 | 1999-03-16 | Futaba Corp | Field emission type image display device and its driving method |
| NO983158L (en) * | 1998-07-08 | 2000-01-10 | Safetel As | Device for creating alternative telecommunications path |
| US6600811B1 (en) * | 1999-05-07 | 2003-07-29 | Lucent Technologies Inc. | Emergency call monitor |
| US6327342B1 (en) | 1999-05-28 | 2001-12-04 | Matthew Stephen Mobley | E911 backup system for emergency 911 call answering systems |
| DE19950546A1 (en) * | 1999-10-20 | 2001-04-26 | Siemens Ag | Method for setting up a protected communication segment between two network elements of a telecommunications network and corresponding telecommunications network |
| US6556672B1 (en) * | 1999-12-07 | 2003-04-29 | Intel Corporation | Fault tolerant voice processing system |
| US6748051B1 (en) * | 2000-04-12 | 2004-06-08 | Network Expert Software Systems, Inc. | 911 status system and method |
| US6519324B1 (en) * | 2000-04-13 | 2003-02-11 | Lucent Technologies Inc. | Method for recovering emergency calls at an operator station during a position failure |
| KR100402138B1 (en) * | 2001-03-30 | 2003-10-17 | (주)위니텍 | Emergency Call Distribute Process and CTI Dual System Dissolving Partial Hindrance for Emergency Rescue System of The Fire Defense Head Quarters |
| US20030013477A1 (en) * | 2001-07-12 | 2003-01-16 | Mcalinden Paul | Controlling dual processors in cellular telephones |
| US7044132B2 (en) * | 2002-08-08 | 2006-05-16 | Medidea, Llc | Surgical drape adapted for use with radiological equipment |
| US7454664B2 (en) * | 2003-06-30 | 2008-11-18 | International Business Machines Corporation | JTAGchain bus switching and configuring device |
| US7680252B2 (en) | 2004-11-08 | 2010-03-16 | Aztek Engineering, Inc. | Switch proxy for providing emergency stand alone service in remote access systems |
| US20060262907A1 (en) * | 2005-05-19 | 2006-11-23 | Sbc Knowledge Ventures Lp | Switching public safety answering points between central offices |
| US7953210B2 (en) | 2005-06-27 | 2011-05-31 | Aztek Engineering, Inc. | Switch proxy for providing emergency stand-alone service in remote access systems |
| US8948367B2 (en) * | 2008-08-19 | 2015-02-03 | Avaya Inc. | Rerouting of trunks by a PBX to an alternate PBX |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3335229A (en) * | 1963-11-05 | 1967-08-08 | Bell Telephone Labor Inc | Arrangement for controlling traffic in a switching network |
| GB1458526A (en) * | 1973-07-26 | 1976-12-15 | Gen Electric Co Ltd | Telecommunications switching networks |
| US3909545A (en) * | 1974-05-02 | 1975-09-30 | Gte Automatic Electric Lab Inc | Emergency transfer circuit for use in a communication switching system |
| US3978291A (en) * | 1974-09-09 | 1976-08-31 | Bell Telephone Laboratories, Incorporated | Automated main distributing frame system |
| US4119815A (en) * | 1977-05-31 | 1978-10-10 | American District Telegraph Company | Central station system including secondary communication path established through commercial telephone network |
| US4286118A (en) * | 1979-07-02 | 1981-08-25 | Solid State Systems, Inc. | Data distribution system for private automatic branch exchange |
| JPS5726955A (en) * | 1980-07-25 | 1982-02-13 | Hitachi Ltd | Backup control system |
| US4400587A (en) * | 1981-08-25 | 1983-08-23 | Rockwell International Corporation | Overflow and diversion to a foreign switch |
| FR2574237B1 (en) * | 1984-11-30 | 1992-05-22 | Telecommunications Sa | SWITCHING SYSTEM FOR A DIGITAL TRANSMISSION NETWORK |
| US4731825A (en) * | 1986-01-27 | 1988-03-15 | Tellabs, Inc. | Nonblocking switching system and method |
| US4807280A (en) * | 1987-09-18 | 1989-02-21 | Pacific Bell | Cross-connect switch |
| GB2222055B (en) * | 1988-08-16 | 1992-10-28 | Plessey Telecomm | Telecommunications transmission security arrangement |
| US4907253A (en) * | 1988-09-07 | 1990-03-06 | Pacific Bell | Cross-connected switch having means for removing switching modules without interrupting service |
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| GB2230678B (en) * | 1989-03-31 | 1993-07-14 | Plessey Telecomm | Improvements in or relating to exchanges |
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| US4943999A (en) * | 1989-05-24 | 1990-07-24 | At&T Bell Laboratories | Switching system reliability |
| US5058105A (en) * | 1990-04-04 | 1991-10-15 | At&T Bell Laboratories | Network alternate routing arrangement |
| US5187706A (en) * | 1990-10-30 | 1993-02-16 | At&T Bell Laboratories | Dual access rings for communications networks |
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-
1992
- 1992-11-12 US US07/975,243 patent/US5454025A/en not_active Expired - Lifetime
-
1993
- 1993-11-10 CA CA002102867A patent/CA2102867C/en not_active Expired - Fee Related
- 1993-11-11 GB GB9323324A patent/GB2273852B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2102867A1 (en) | 1994-05-12 |
| GB2273852A (en) | 1994-06-29 |
| GB2273852B (en) | 1997-01-15 |
| GB9323324D0 (en) | 1994-01-05 |
| US5454025A (en) | 1995-09-26 |
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