WO1998014844A1

WO1998014844A1 - Telecommunications disaster recovery system

Info

Publication number: WO1998014844A1
Application number: PCT/US1997/017093
Authority: WO
Inventors: William J. Black; Mark L. Smith; Scot L. Dowell
Original assignee: The Timken Company
Priority date: 1996-10-04
Filing date: 1997-09-30
Publication date: 1998-04-09

Abstract

A telecommunications disaster recovery system (10) provides telecommunications service to a customer premises during failure of a normal operating mode of the system. Certain customer premises termination equipment (15) considered critical for ongoing operation of a business are connected to a primary PBX (12) during the normal mode of operation, and to a secondary PBX (14) during failure of the normal operating mode. A control unit (40) is provided that includes one manually-actuated control switch (49) for each building or location containing critical termination equipment. Each control switch (49) is open during the normal mode of operation, and closed during failure of the normal mode of operation. One remote switching station (26) is operatively connected to each control switch (49), the primary PBX (12), the secondary PBX (14) and the critical termination equipment (15) associated with the particular building or location. The remote switching station (26) switches the corresponding critical termination equipment (15) to the primary or secondary PBX system (12, 14) based upon the position of the control switch (49).

Description

TELECOMMUNICATIONS DISASTER RECOVERY SYSTEM

Background Art

This invention relates to telecommunications, and in particular to a disaster recovery system for a telecommunications network that switches certain critical extensions to a backup switching system such as a private branch exchange (PBX) when a main switching system fails.

While telecommunications companies control local switching systems that interconnect local loops associated with a public network, many business subscribers employ a switching subsystem such as a PBX at the customer premises to interconnect various customer premises termination equipment such as telephones, data terminals, facsimile machines and modems. PBXs are capable of switching voice and data transmissions across many extensions or lines. For example, a PBX systems sold by AT&T under the federally registered trademark DEFINITY is capable of supporting up to 32,000 lines, and Northern Telecom's MERIDIAN 1 PBX system has a maximum capacity of 60,000 lines. This allows large corporate users that have several buildings on a campus to connect many, or all, extensions to one main PBX system. Other corporate users having offices throughout a city or state (or even nationwide) may employ a PBX network including two or more interconnected PBX systems.

If such a PBX system fails for any reason, all telecommunication facilities and extensions supported by the system go off line. In this situation, an entire corporation effectively could be paralyzed until the PBX system ^"becomes operational. Backup systems have been designed to allow for continued operation of lines connected to a defective PBX system. For example, U.S. Patent No. 5,214,692, issued May 25, 1993 to Chack et al., discloses a digital bypass unit for a PBX or ACD (automatic call distributor) telephone system that allows for telephone calls to be placed or received on a Tl digital span using a digital telephone set if the PBX or ACD system fails. During power or system failure, Tl channels automatically are connected directly to digital telephone sets by relays switching connections associated with the bypass unit. The bypass unit also allows for queuing and distribution of incoming calls to the next available agent. While the '692 patent does simulate certain functions that can be performed by a PBX system, it fails to fully provide the control, functionality and versatility associated with conventional PBX systems that typically service large business subscribers. Similarly, the '692 patent appears to be directed only to customer premises equipment (CPE) such as digital telephone sets, and fails to provide backup support for other CPE such as analog termination equipment or connections, data terminal equipment, and other digital equipment (e.g., voice station sets, modems and facsimile machines).

Other PBX backup systems connect lines directly to a telecommunications company's central office trunks during failure of a primary PBX system. For example, DEES Communications Engineering Ltd., 4130 148th Avenue NE, Redmond, WA 98052, sells a Powerfail Bypass Unit, having model numbers 154, 154A and A500, that automatically bypasses the PBX system and switches up to eight central office trunks to preselected stations during power failure at the PBX. The DEES unit is normally controlled by the user's PBX or by a manual switch located on the unit itself.

Similarly, U.S. Patent No. 4,575,584, issued March 1 1, 1986 to Smith et al., discloses a fail-safe digital telephone set that is normally connected to a PBX. In the event of PBX failure, a switching element associated with the phone switches connection from the PBX to an analog telephone line to allow for analog signal transmission bypassing the PBX. However, these backup systems lack the computerized programmed control associated with switching and ancillary functions typically performed by the primary PBX system. The '584 device also does not allow digital signal transmission when operating in the bypass mode. Therefore, it is desirable to have a telecommunications backup system that allows continuous operation of critical extensions connected to a primary PBX system when the primary PBX system fails. This backup system should provide programmed control of switching and ancillary functions that otherwise would be performed by the primary PBX system. Such a backup system should be easily installed at a customer premises, and readily expandable to accommodate additional extensions, if desired. Indication should be provided when the backup system is in operation, as well as when a backup power supply is employed.

Summary of the Invention

Accordingly, one object of the present invention is to provide a new and improved telecommunications disaster recovery system that allows for critical lines switched by a primary switching system to be switched by a secondary backup switching system in the event of primary system failure.

Another object of this invention is to provide a telecommunications disaster recovery system wherein the secondary switching system performs switching and ancillary functions that otherwise would be performed by the primary switching system. Another object of this invention is to provide a telecommunications disaster recovery system that provides audio or visual indication when the secondary switching system is activated for a particular critical extension or group of critical extensions connected to a remote switching station.

Still another object of this invention is to provide a telecommunications disaster recovery system that activates an alarm when the switching panel is powered by a backup power source.

Another object of this invention is to provide a telecommunications disaster recovery system that is easily installed at the customer premises. Yet another object of this invention is to provide a telecommunications disaster recovery system that is readily expandable to accommodate additional critical extensions.

These and other objects and advantages will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings.

In accordance with the invention, generally stated, a telecommunications system is disclosed for providing telecommunication service to a customer premises during failure of a normal operating mode of the system. The system includes a plurality of termination equipment located at the customer premises. A primary switching system located at the customer premises such as a private branch exchange (PBX) system operatively connects each of the termination equipment to one of a plurality of telecommunication lines or circuits extending between a customer premises and a telecommunication company central office during the normal operating mode of the primary switching system. The system also includes a secondary switching system located at the customer premises (e.g., a PBX system) for operatively connecting the termination equipment to the telecommunication lines during failure of the normal operating mode of the primary switching system. Control circuitry is provided that includes a control switch having a first position during the normal mode of operation of the primary switching system, and a second position during failure of the normal mode of operation. Further included in the system is a switching device that is operatively connected between the termination equipment and the primary and secondary PBX systems for switchably connecting the termination equipment to the primary switching system or the secondary switching system based upon the position of the control switch. More specifically, the switching device connects the termination equipment to the primary switching system during the normal mode of operation, and connects the termination equipment to the secondary switching system during failure of the normal mode of operation. Means is further provided for visually indicating whether the termination equipment is connected to the primary switching system or the secondary switching system. In the preferred embodiment, this includes two LEDs operatively connected to switches associated with the switching device, where one LED is energized during the normal mode of operation, and the other LED is energized during failure of the normal mode of operation. Additional means is provided for visually indicating whether a primary power source or a backup power source is supplying power to the switching device.

The switching device also includes a relay for establishing an electrical path between the control circuitry and the switching device when the control switch is maintained in its second position. This allows for transmission of a control signal from the control circuitry to the switching device via the electrical path. The switches associated with the switching device are actuated from the first position into the second position upon receipt of the control voltage from the control circuitry during failure of the normal operating mode. When the normal operating mode is restored after temporary failure, the control switch is switched from the second position to the first position, thereby terminating flow of the control signal to the switching device via the relay and actuating said switches of the switching device from the second position into the first position. Yet another aspect of the present invention is that of a method for providing telecommunications service to a plurality of termination equipment located at a customer premises during failure of a normal mode of operation of a primary PBX, comprising the steps of: connecting the termination equipment to the primary PBX during the normal mode of operation; providing visual indication to a user that the termination equipment is connected to the primary PBX during the normal mode of operation; disconnecting the termination equipment from the primary PBX, and connecting the termination equipment to a backup PBX during failure of the normal operating mode of the primary PBX; providing visual indication to the user that the termination equipment is connected to the backup PBX during failure of the normal operating mode of the primary PBX; and disconnecting the termination equipment from the backup

PBX, and connecting the termination equipment to the primary PBX when the normal operating mode of the primary PBX is restored after a temporary failure.

Other objects and features will be apparent and in part pointed out hereinafter.

Brief Description of Drawings

The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings which form a part of the specification. FIG. 1 is a schematic block diagram of the telecommunications disaster recovery system of the present invention;

FIG. 2 is a schematic diagram of the preferred remote switching station of the present invention;

FIG. 3 is a sectional front plan view of a switch panel associated with a remote switching station, showing the wiring configuration of the primary and secondary PBX systems and critical extensions supported by the remote switching station; and

FIG. 4 is a schematic diagram illustrating the electrical circuitry and interconnection of the master panel for the remote switching station, the control unit, and the primary and backup power supplies.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Best Mode for Carrying Out the Invention Referring now to FIG. 1 , there is shown a telecommunications system of the present invention, indicated generally at 10, for switching certain extensions of a business customer from a primary switching system 12 to a secondary switching system 14 when the primary switching system 12 is not operational. Any private switching system or equipment located at the customer premises that controls signal transmissions to and from customer premises equipment (CPE) 15 can be used as the primary or secondary switching systems 12, 14 in the present invention. In the preferred embodiment, the primary and secondary switching systems 12, 14 are private branch exchanges (PBXs). Any type of PBX system can be used in the present invention, including analog or digital PBXs, as well as automatic, electronic or computerized PBXs. In a public telecommunications network, the customer premises switching systems are operatively connected to a telecommunications network element or switching system (not shown) located at a telecommunications company's central office (not shown) via telecommunications lines or circuits (local loops). The primary or secondary switching system connects CPE to the local loop, thereby allowing for signal transmission to and from the CPE in a manner known in the art.

Within a business, certain extensions 16 connected to particular CPE 15 or used by certain personnel are considered essential for continuous operation of the business. For example, if the primary PBX system supports 5,000 extensions, only 900 of those extensions may be considered critical for the ongoing operation of the business. Regardless of whether one or all of the extensions are considered critical, the telecommunications system 10 of the present invention provides that critical extensions 16 are routed to the backup PBX 14 when the primary PBX system 12 fails. FIG. 1 illustrates the interconnection of a plurality of CPE 15 located in several buildings or locations on a business campus to the primary PBX 12. The telecommunications system 10 of the present invention can be used for any business customer having extensions controlled by a private switching system, regardless of whether the business campus includes one or many buildings or locations. CPE 15 includes, for example, any analog or digital termination equipment, such as telephone sets; key telephone equipment; CRTs and other data terminals; printers; computers; modems; channel service units (CSUs); recording, answering and voice mail equipment; facsimile machines; video conferencing cameras and any other voice, data or video telecommunication equipment. The telecommunications system 10 includes intrabuilding wiring 17 that extends from a distribution frame 18 throughout each building on the business campus to the CPE 15. The distribution frame 18 typically is located inside a wire closet, usually found in the basement of the building. The intrabuilding wiring 17 then is operatively connected to intrapremises wiring 20 extending from the distribution frame 18 to the primary PBX 12. The primary PBX 12 can be located in a separate building or remote location with respect to all or some CPE 15.

As mentioned above, the backup or secondary PBX 14 controls signal transmissions to and from certain CPE 15 connected to critical extensions 16 in the event that the primary PBX 12 fails or becomes inoperable for any reason (e.g., power failure, fire, short or grounding). The secondary PBX 14 preferably is placed at a remote location when compared to the location of the primary PBX (e.g., in separate buildings located at opposite ends of the business campus). The remote location of the backup PBX 14 reduces the risk of failure or destruction of both the primary and secondary PBXs 12, 14 in the event that fire or some other disaster destroys a portion of the business campus.

The telecommunications system 10 also includes a remote switching station 26 that switches the critical extensions 16 from the primary PBX 12 to the backup PBX 14 when the primary PBX 12 is not operational. As shown in FIG. 1, the remote switching station 26 preferably is located in close proximity to the distribution frame 18 within the wire closet of each building containing critical extensions 16 supported by the backup PBX 14. For example, when three separate buildings or locations contain critical extensions 16 (as shown in FIG. 1), a remote switching station 26 is installed at each building or locations near the distribution frame 18. Only the critical extensions 16 are connected to the remote switching station 26. Noncritical extensions are wired directly to the primary PBX 12 via intrapremises wiring 20 in a conventional fashion known in the art. As discussed below in greater detail and shown in FIG. 2, the remote switching station 26 includes one or more switches or switching devices 28 where each switch 28 is operatively connected to one critical extensions 16 of the building or location in which the remote switching station 26 is disposed. FIG. 3 shows the wiring configuration of the primary and secondary PBX systems 12, 14 and critical extensions 16 supported by the remote switching station 26. The extensions 16 shown in FIG. 3 are operably connected to the primary PBX 12. As best illustrated in FIG. 4, each switch 28 has a first position for connecting the associated critical extension 16 (and CPE 15) to the primary PBX 12 via intrabuilding wiring 29 and intrapremises wiring 20 during normal operation of the telecommunications system 10. The switch 28 also has a second position for connecting the CPE 15 to the backup PBX 14 via wiring 30 upon failure of the primary PBX 12.

To provide continuous power to the remote switching station 26, a conventional uninterruptible power supply (UPS) 31 preferably is employed. Under normal operating conditions, local alternating current (ac) line voltage (e.g., 1 10 volt ac power) is supplied to the UPS 31 as a primary power supply 32. If there is an internal failure of the UPS 31, the UPS 31 is automatically bypassed such that the remote switching station 26 is powered by unconditioned local ac line voltage of the primary power supply 32. In the event of local power failure, the UPS 31 is powered by a battery power source associated with the UPS 31. If the ac line power is interrupted for longer than several minutes, a backup engine generator 34 operably connected to the UPS 31 is used to provide power to the remote switching station 26 for an extended period of time. When the generator 34 comes up to speed, the UPS 31 supplies power from the generator 34 to the remote switching station 26. If the generator fails to start, the battery power source of the UPS 31 in the preferred embodiment can provide power to the remote switching station 26 for up to approximately 1.5 hours. When local ac power is restored, the UPS 31 supplies power from the primary power source 32 to the remote switching station 26. Switching functions performed by each remote switching station 26 are controlled by a control unit 40 disposed in close proximity to the secondary PBX 14. The remote switching stations 26 are operatively connected to the control unit 40 via intrapremises wiring 42 and 64. FIG. 4 is a schematic diagram of the electrical circuitry associated with one remote switching station 26 and the control unit 40. The remote switch station 26 includes a master panel 44 having one or more switches 28 (as discussed above and below) for connecting the critical extensions 16 to either the primary or secondary PBX 12, 14. The station 26 also includes a current limiting resistor Rl, and two relays RYl and RY2 that perform certain switching functions and transmit a signal to the control unit 40 when the remote switching station 26 is powered by the backup power supply 34 (via the UPS 31) in the event of local power failure. In the preferred embodiment shown in FIG. 4, relay RYl is a single pole, single throw relay, and relay RY2 is a double pole, double throw relay. However, other switching devices performing in a substantially similar manner as relays RYl and RY2 can be used in the present invention in place of relays RYl and RY2.

As mentioned above, the number of switches 28 associated with the remote switching station 26 is based upon the number of critical extensions 16 supported by the remote switching station 26. For example, if the master panel 44 contains twenty switches 28, the master panel 44 can support up to twenty critical extensions 16 since each extension 16 is connected to one switch. If additional switches are needed to support additional critical lines, one or more slave panels 46 are daisy-chained to or connected in series with the master panel 44 as shown in FIG. 2. Each slave panel 46 includes a plurality of switches 28 which can be used to support additional critical extensions 16. The ability to connect additional switches 28 to the remote switching station 26 by daisy- chaining slave panels 46 to the master panel 44 allows the telecommunications system 10 of the present invention to be easily expandable to accommodate additional critical extensions 16 as needed. In the preferred embodiment of the present invention, Powerfail Bypass Units, Model 154A, sold by DEES Communications Engineering Inc., 4130 148th Avenue NE, Redmond, WA 98052, are used to provide the necessary switching between the primary PBX 12 and the secondary PBX 14 for each critical extension 16. Power cubes (not shown) are plugged into the UPS 31 to convert 1 10 volts alternating current (ac) to 24 volts direct current (dc) power, and supply 24V dc power to the DEES units. Two DEES units are included in the master panel 44 associated with the remote switching station 26, where each DEES unit is capable of switching up to eight critical extensions 16 between the primary and secondary PBXs 12, 14. If more than sixteen critical extensions 16 exist at a building or location, one or more slave panels 46 are daisy-chained to the master panel 44, where each slave panel 46 contains two DEES units. Therefore, if sixty (60) critical extensions 16 exist in a particular building, the remote switching station 26 of the preferred embodiment includes three series connected slave panels, providing support for up to sixty-four (64) extensions. If forty (40) additional extensions 16 need to be added to that remote switching station 26 at a later time, three additional slave panels 46 can be added, allowing for up to 112 extensions to be connected to the remote switching station 26. While the DEES units are used in the preferred embodiment, any other similar switch panels can be used in the present invention. The switches 28 associated with the switch panels 44, 46 preferably have an A/B switch configuration as discussed below that can be controlled remotely.

The switches 28 associated with the DEES units and shown in FIG. 4 are auxiliary switches, with each switch having two sets of auxiliary contacts, namely a " " contact 47 and a "&" contact 48. The auxiliary switches are relay devices internally mounted in the DEES units. The a contact 47 is open during normal operation of the primary PBX system 12, and closed when the backup PBX 14 is used to control the attached critical extensions 16. The b contact 48 associated with each auxiliary switch 28 has a normally closed position which establishes an electrical path between the primary PBX and the CPE 15 associated with critical extension 16 connected thereto during normal operation of the telecommunications system 10. When the b contact 48 is maintained in its normally closed position, the a contact 47 is maintained in a normally open position as shown in FIG. 4. When the a contact is actuated into its closed position, the b contact is actuated into an open position.

When the a and b contacts 47, 48 are moved from their standard reference positions, the critical extension 16 connected to the switch 28 is disconnected from the primary PBX 12 and connected to the secondary PBX 14. While auxiliary switches are used in the preferred embodiment of the present invention, any other switch configuration can be employed in the present invention that allows for switching between the primary and secondary PBXs 12, 14 in a substantially similar manner as discussed herein. For example, manual toggle switches, key switches or rocker switches can be used in the system 10. FIG. 4 illustrates four auxiliary switches 28 associated with the master panel 44 of the present invention. Circuitry associated with the control unit 40 also is illustrated in FIG. 4. The control unit 40 includes a manually operable control switch 49 that is used to control the actuation of the switches 28 associated with each remote switching station 26. As discussed below in greater detail, the remote switching station 26 is responsive to the position of the control switch 49. The remote switching station 26 connects the critical extensions to the primary PBX 12 when the switch is in a first or open position during normal operation of the system 10. During failure of the normal mode of operation for the system 10, the remote switching station 26 connects the critical extensions 16 to the secondary PBX 14 when the control switch 49 is in a second or closed position. As discussed below, when the control switch 49 is closed or in the second position, an electrical path is established that allows for the transmission of a control voltage signal from the control unit 40 to the corresponding remote switching station 26. The control voltage triggers the switches 28 to change state from their standard reference positions, thereby effectively connecting the critical extensions 16 to backup PBX 14.

The number of control switches 49 included in the control unit 40 is based upon the number of remote switching stations 26 installed on the business campus, where one control switch 49 is operatively connected to each remote switching station 26. This circuitry configuration allows each building or location served by a remote switching station 26 to be selectively connected to the backup PBX 14 in the event only one area's extensions 17 go off line due to a cable cut, partial PBX failure or the like. In this situation, the primary PBX 12 can continue to control all other extensions, while the critical extensions 16 affected by the problem are controlled by the secondary PBX 14 until the problem is corrected.

As shown in FIG. 4, the control unit 40 also includes visual indicators 50 for each remote switching station 26 connected thereto. These indicators 50 indicate whether the critical extensions 16 connected to a particular remote switching station 26 are connected to the primary or secondary PBX 12, 14, and whether the remote switching station 26 is powered by local line power or the backup power source 34. In the preferred embodiment shown in FIG. 4, the visual indicators 50 include a green light emitting diode (LED) 52 and a red LED 54. As will be discussed in greater detail below, the green LED 52 is energized when the primary PBX 12 controls the operation of critical extensions 16 connected to the associated remote switching station 26. When the red LED 54 is energized, the control switch 49 is in its closed position such that the operation of these critical extensions 16 is controlled by the backup PBX 14. When the backup power supply is activated, the energized indicator (e.g., the red LED 54) blinks. As will be discussed below, an alarm signal also is transmitted to a computer screen (not shown) associated with a computerized monitoring system 56 in this situation, indicating a power problem exists at a particular building or location that requires dispatch of an electrician to restore power to that location. In the event that the primary PBX 12 (or any part thereof) fails or becomes inoperable for whatever reason, the control switches 49 of the control unit 40 are manually actuated into the closed position. In this situation, the normally closed b contacts 48 associated with the auxiliary switches 28 of the remote switching stations 26 are opened, and normally open a contacts 47 are closed. When this occurs, the critical extensions 16 effectively are switched from the primary PBX 12 to the secondary PBX 14. The visual indicators 50 also indicate the backup PBX 14 is controlling signal transmissions to and from all associated critical extensions 16. In the preferred embodiment, the red LED 54 is energized when all a contacts 47 associated with the corresponding remote switching station 26 are closed. If a remote switching station 26 fails to respond to the signal from the control unit 40 by illuminating the second visual indicator 54 after the control switch 49 is closed, the nonresponsive master or slave panels 44, 46 can be manually switched to close the a contacts 47 and establish the connection with the backup PBX 14.

The critical extensions 16 are controlled by the backup PBX 14 until the primary PBX 12 is operational. When the primary PBX 12 or associated problem is repaired, the control switches 49 are manually switched to the normally open positions, thereby terminating the transmission of the control voltage signal to the remote switching unit 26. As will be discussed below, this triggers the auxiliary switches 28 to return to their standard reference positions, effectively reconnecting the critical extensions 16 to the primary PBX system 12. When critical extensions 16 are returned to normal operation, the visual indicators show the extensions are controlled by the primary PBX 12. When digital CPE 15 is connected to the critical extensions 16 and the

DEES units are used as the switch panels 44, 46, the secondary PBX 12 must be reset when the connections are switched back to the primary PBX 12. Before the DEES units switch an extension 16 from the secondary PBX 14 to the primary PBX 12, the DEES units determine whether CPE 15 connected to that extension is off-hook, and if so, do not switch the extension 16 to the primary is -

PBX 12 until the CPE 15 returns to an on-hook condition. The DEES unit determines whether the CPE 15 is on-hook or off-hook based upon whether current is supplied to that extension 16, indicating the extension 16 is off-hook. However, digital CPE 15 (e.g., digital telephones) always draws some current, even when on-hook and not in use. Therefore, the DEES units associated with the remote switching station 26 interpret this current draw by the digital CPE 15 as an off-hook condition, and prevent the contacts from switching from the secondary PBX 14 to the primary PBX 12. To reconnect the extensions 16 to the primary PBX 12, the manual control switch 49 is returned to its primary or normally open position, and then ports associated with the secondary PBX 14 are reset. This allows the contacts 47, 48 associated with the auxiliary switches 28 to return to their standard reference positions, thereby reconnecting the critical extensions 16 to the primary PBX 12. If an analog PBX system 14 is used to control the operation of analog CPE 15, then it is not necessary to reset the backup PBX 14. Moreover, if the DEES units are not employed as the switch panels 44, 46, the reset procedures set forth above may not be necessary.

As shown in FIGS. 2 and 3, power is supplied to the master panel 44 circuitry and slave panel 46 circuitry via the current limiting resistor Rl . In the preferred embodiment, resistor Rl has a resistance value of 4.7 kΩ. As discussed above, FIG. 4 illustrates the standard reference positions of the auxiliary switches 28 during normal operation of the telecommunications system 10. Current is supplied to the green LED 52 via the b contacts 48 associated with the auxiliary switches 28 and intrapremises wiring 42 connecting the remote switching station 26 to the control unit 40. As discussed above, energization of the green LED 52 indicates the critical extensions 16 associated with the particular building or location are controlled by the primary PBX 12.

If the primary PBX 12, or any portion thereof, is not operating properly, the control switches 49 on the control unit 40 that correspond to the particular buildings or locations affected by this problem are manually switched into the closed position until the primary PBX 12 is operational. In this situation, one terminal of a coil 60 associated with relay RYl is grounded, thereby energizing the relay coil 60 and closing a normally open relay contact 62 associated with the relay RYl . When the relay contact 62 is closed, an electrical path is established via intrapremises wiring 64 that allows for flow of the control voltage signal from the control unit 40 to the remote switching station 26. As discussed above, upon receipt of the control signal, auxiliary switches 28 of the remote switching station 26 change state, thereby establishing electrical connection between the critical extensions 16 and the secondary PBX 14. Power supplied from the UPS 31 is rerouted to the red LED 54 (via the a contacts 47 and intrapremises wiring 42), thereby indicating the corresponding remote switching station 26 is operating in a emergency or backup mode, bypassing the primary PBX 12 and operatively connecting associated critical extensions 16 to the secondary PBX 14. As mentioned above, all master and slave panels 44, 46 (e.g., all DEES units) associated with each remote switching station 26 must respond before the red LED 54 is illuminated. If one or more such panels or DEES units fail to switch connections from the primary PBX 12 to the backup PBX 14, the second visual indicator does not energize. In this situation, a technician or other individual can travel to the location of the remote switching station 26 to manually switch the panels to the secondary PBX 14.

Relay RY2 is provided to signal a trouble condition or local ac power loss for each remote switching station 26. If local ac power is lost, the generator 34 and battery power source associated with the UPS 31 are activated automatically to supply power to the remote switching station 26. As discussed above, the battery power source supplies power until the generator becomes operational, allowing for continued operation of the remote switching station 26. When the UPS 31 is activated, relay RY2 is turned on and off at a rapid rate. Relay RY2 includes a first set of relay contacts 66 that transmits an alarm message signal to the computerized monitoring system 56, indicating a trouble condition is present at the location of the remote switching station 26. A second set of relay contacts 68 associated with the relay RY2 repeatedly short circuits the visual indicators 50, causing the energized indicator (e.g., the red LED 54) on the control unit 40 to rapidly blink off and on, indicating the location of the local power failure. When local ac power is restored, the control unit 40 automatically resets itself, and the appropriate visual indicator 50 (e.g., the red LED 54) returns to its normal state of constant illumination as long as the backup PBX 14 controls the operation of the critical extensions 16.

The foregoing description is set forth only for illustrative purposes only and is not meant to be limiting. Numerous variations, within the scope of the appended claims will be apparent to those skilled in the art in light of the foregoing description and accompanying drawings. Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

Claims

1. A telecommunications system for providing telecommunication service to a customer premises during failure of a normal operating mode of the system, comprising: a plurality of termination equipment located at the customer premises; a primary switching system located at the customer premises for operatively connecting each of said termination equipment to a telecommunication line extending between a customer premises and a telecommunication company central office during the normal operating mode of the primary switching system; a secondary switching system located at the customer premises for operatively connecting said termination equipment to the telecommunication lines during failure of the normal operating mode of the primary switching system; control circuitry including a control switch having a first position during the normal mode of operation of the primary switching system, and a second position during failure of the normal mode of operation; and a switching device for switchably connecting said termination equipment to said primary switching system during the normal mode of operation, and connecting said termination equipment to said secondary switching system during failure of the normal mode of operation.

2. The telecommunications system of claim 1 wherein said switching device includes a plurality of switches having a first position for operatively connecting said termination equipment to said primary switching system when said control switch is maintained in the first position, and a second position for operatively connecting said termination equipment to said secondary switching system when said control switch is maintained in the second position, each of said termination equipment being operatively connected to one of said switches associated with said switching device.

3. The telecommunications system of claim 2 wherein said switching device includes a relay for establishing an electrical path between said control circuitry and said switching device when said control switch is maintained in its second position, thereby allowing for transmission of a control signal from said control circuitry to said switching device via the electrical path, said switches being actuated from the first position into the second position upon receipt of the control voltage from the control circuitry during failure of the normal operating mode.

4. The telecommunications system of claim 3 wherein said control switch is switched from the second position to the first position when the normal operating mode is restored after temporary failure, thereby terminating flow of the control signal to the switching device via said relay and actuating said switches of said switching device from the second position into the first position.

5. The telecommunications system of claim 4, further including means for visually indicating whether said termination equipment is connected to the primary switching system or the secondary switching system.

6. The telecommunications system of claim 5 wherein said visual indication means includes a first light emitting diode (LED) and a second LED operatively connected to said switches of said switching device, said first LED being energized and said second LED being deenergized when said switches are in the first position, said second LED being energized and said first LED being deenergized when said switches of said switching device are in the second position.

7. The telecommunications system of claim 6, further including an alternating current (ac) power source for supplying current to said switching device, and a backup power supply for supplying to said switching device upon failure of said ac power source, and means for visually indicating whether said ac power source or said backup power supply is supplying power to said switching device.

8. The telecommunications system of claim 7 wherein said power indication means includes a relay operatively connected between said ac power supply and said backup power supply, said relay having a first set of contacts maintained in a normally open position when said ac power source is supplying power to said switching device, the first set of relay contact being opened and closed at a rapid rate when the backup power supply supplies power to said switching device, thereby turning said visual indication means on and off at the rapid rate when said backup power supply supplies power to said switching system.

9. The telecommunications system of claim 8 wherein said relay includes a second set of relay contacts operatively connected to a computer monitoring system having a normally open position when said ac power source supplies power to said switching device, said second set of relay contacts being opened and closed at the rapid rate during operation of said backup power supply, thereby generating an alarm signal during operation of said backup power supply that is transmitted to the computer monitoring system to provide indication of failure of said ac power source.

10. The telecommunications system of claim 2 wherein said switches are auxiliary switches including a first auxiliary contact having a normally open position during the normal mode of operation and a closed position during failure of the normal mode of operation, and a second auxiliary contact having a normally closed position during the normal mode of operation and an open position during failure of the normal mode of operation, said switches being maintained in the first position when said first contact is open and said second contact is closed, said switches being maintained in the second position when said first contact is closed and said second contact is open.

1 1. The telecommunications system of claim 1 wherein the control switch is manually actuated.

12. The telecommunications system of claim 1 wherein said primary switching system is a private branch exchange system.

13. The telecommunications system of claim 1 wherein said secondary switching system is a private branch exchange system.

14. A telecommunications system for providing ongoing telecommunication service during failure of a normal mode of operation of the system, comprising: a plurality of termination equipment disposed inside one or more buildings at a customer premises, said termination equipment including one or more critical components; a primary private branch exchange (PBX) system for operatively connecting each of the termination equipment to one of a plurality of telecommunications circuits extending between a telecommunications company central office and the customer premises during the normal operating mode of the telecommunications system; a secondary PBX system for operatively connecting each of the critical components of the termination equipment to one telecommunications circuit upon failure of the normal operating mode, thereby allowing for signal transmissions to and from each critical component during failure of the normal operating mode; one or more switching assemblies including a series combination of voltage activated switching devices operatively connected to the critical components and the primary and secondary switching systems, said switching devices switchably connecting the critical components to the primary PBX system during the normal operation mode, and to the secondary PBX system during failure of the normal operating mode; control circuitry including one control switch for each switching assembly, each control switch having an open position during the normal mode of operation, and a closed position during failure of the normal mode of operation, said switching assembly connecting the critical components to the primary PBX system or the secondary PBX system based upon the position of the control switch; and a relay operatively connected between each control switch and switching assembly, including a relay contact having a normally open position when the control switch is open, and a closed position when said control switch is closed for establishing an electrical path between said control circuitry and said switching assembly during failure of the normal mode of operation, a control voltage signal being supplied from the control circuitry to the switching device via the electrical path when the relay contacts are closed, the control voltage signal triggering the switching devices to connect the critical components to the secondary PBX system.

15. The telecommunications system of claim 19, further including a light emitting diode (LED) operatively connected to each series combination of switching devices, said first LED being energized when the corresponding series combination of switching devices operatively connects the corresponding critical components to the primary PBX system, and deenergized when the switching devices connect the critical components to the secondary PBX system; and a second LED operatively connected to each series combination of switching devices, said second LED being energized when the corresponding series combination of switching devices connects the corresponding critical components to the secondary PBX system, and deenergized when the switching devices connect the critical components to the primary PBX system.

16. The telecommunications system of claim 14 wherein one switching assembly is disposed inside each building on the customer premises containing one or more critical components.

17. The telecommunications system of claim 16 wherein the secondary

PBX system is disposed at a distant location on the customer premises with respect to the location of the primary PBX system, and the control circuitry is disposed in close proximity to the secondary switching system.

18. In a telecommunications system including a plurality of termination equipment located in various locations at a customer premises, the improvement comprising: a primary private branch exchange (PBX) system for operatively connecting each of said termination equipment to one of a plurality of telecommunication lines extending between a customer premises and a telecommunication company central office during a normal operating mode of the primary PBX system; a secondary PBX system for operatively connecting each of said termination equipment to one telecommunication line during failure of the normal operating mode of the primary switching system; a control apparatus including a manually actuated control switch having a first position during the normal mode of operation of the primary PBX system, and a second position during failure of the normal mode of operation; and at least one switching device operatively connected between said termination equipment and said primary and secondary PBX systems for switchably connecting said termination equipment to said primary PBX system or said secondary PBX system based upon the position of the control switch, said switching device connecting said termination equipment to said primary PBX system when said control switch is maintained in the first position, and connecting said termination equipment to said secondary PBX system when said control switch is maintained in the second position.

19. A method for providing telecommunications service to a plurality of termination equipment located at a customer premises during failure of a normal mode of operation of a primary PBX, comprising the steps of: connecting the termination equipment to the primary PBX during the normal mode of operation; providing visual indication to a user that the termination equipment is connected to the primary PBX during the normal mode of operation; disconnecting the termination equipment from the primary PBX, and connecting the termination equipment to a backup PBX during failure of the normal operating mode of the primary PBX; providing visual indication to the user that the termination equipment is connected to the backup PBX during failure of the normal operating mode of the primary PBX; and disconnecting the termination equipment from the backup PBX, and connecting the termination equipment to the primary PBX when the normal operating mode of the primary PBX is restored after a temporary failure.

20. The method of claim 19, further including the step of providing visual indication to the user when a local alternating current (ac) line power supply for the customer premises fails.