Patent Publication Number: US-7912203-B2

Title: Method and apparatus for providing called party information to a coverage point during survivable processor operation

Description:
FIELD 
     The present invention is directed to providing call coverage routines. In particular, embodiments of the present invention provide called party information to a coverage point while a branch system associated with a called extension is in survivable processor mode. 
     BACKGROUND 
     Voice telephony systems often provide call coverage for calls that are not answered by a called endpoint or extension. Furthermore, a telephony system will typically permit a sequence of alternate destinations or coverage points to be defined for each extension on the telephony system. The coverage paths are usually stored as instructions in a data base that is referenced when coverage for a call is required. 
     In a typical private branch exchange system (PBX), a number of communication endpoints, each having a unique extension, are associated with a communication server. Furthermore, a private branch exchange may include a number of subsystems that each include a communication server and a number of extensions. For example, in a typical implementation, a main or central system may be interconnected to one or more remote branch systems by a wide area network (WAN). Furthermore, various coverage operations may be provided to extensions associated with remote branches by the main system server or some other server that is accessed from remote branches over a wide area network connection. Examples of call coverage services provided by a central system include voice mail coverage. 
     During normal operation, coverage for an extension may be provided by forwarding the call across a local area network from a gateway or communication server that received the call, to the coverage point. In such a situation, the extension of the call communication endpoint is provided as part of the call coverage operation. However, when the gateway or communication server of the system receiving a call is unable to connect to the coverage point, for example due to a WAN outage, the call must be forwarded to the coverage point over an alternate path. Such an alternate path may be provided by the public switched telephony network (PSTN). However, routing a call to a coverage point across the PSTN is typically performed without providing the coverage point with an indication of the extension that was called. Accordingly, upon receiving a call requiring coverage from the PSTN, the coverage point must request information identifying the called extension from the calling party, for example by playing a recorded message requesting that the calling party re-enter the called extension. Furthermore, prior art solutions for implementing coverage paths do not easily accommodate coverage paths that are to be used only under particular circumstances, such as where a branch system is unable to connect to a main or central system over a WAN, and is therefore operating in a local survivable processor mode. 
     Another problem with distributed PBX systems having separate branches (or a branch and central system) that are connected by an Internet protocol network, such as a wide area network, that becomes unavailable relates to calls between extensions associated with different branches. In such a situation, calls between extensions in different branches (or between a branch and a central system) fail if the caller enters only the extension of the called number. Furthermore, in such situations, the caller will be unable to reach the called extension unless the caller knows the complete telephone number for the called party, in order to allow the call to be routed over the public switched telephony network. 
     PBX systems that allow coverage arrangements having multiple coverage points, including coverage points accessed across the PSTN, have been available. In order to forward a call across the PSTN for coverage with an identification of the called extension, those systems require that a coverage path including the telephone number of the coverage point and the extension of the called endpoint be coded for each extension. However, providing such a unique coverage path script for each extension in a system having a large number of extensions is impractical. Furthermore, many private branch exchange systems limit the number of coverage paths that may be administered, making the administration of a unique coverage path for each extension impossible. Even if the number of coverage paths that can be defined is unlimited, administering a unique coverage path for each extension would be an administrative burden. 
     SUMMARY 
     The present invention is directed to solving these and other problems and disadvantages of the prior art. In accordance with embodiments of the present invention, special characters are defined for use in connection with scripts establishing call coverage paths. More particularly, special characters that influence the coverage operation and/or the digits sent to a coverage point may be defined. Through the application of such special characters, a secondary coverage point for use when a network connection between a system associated with a called extension and a primary coverage point is unavailable can be created and used for multiple extensions, without requiring specific administration for each such extension. More particularly, the coverage path in accordance with embodiments of the present invention provides for the communication of an identification of the called extension to the coverage point, without requiring a unique coverage path script for each extension using that coverage point. In accordance with further embodiments of the present invention, a coverage path that results in a public switched telephony network (PSTN) trunk call from a branch system that is temporarily isolated due to the unavailability of a primary network connection can be defined that is only used when the branch system is so isolated. 
     In accordance with the embodiments of the present invention, a coverage path including special variable characters is provided. A first special character may indicate that the coverage path is only for use when the branch system receiving a call that requires coverage from a coverage point or a main system is isolated from the main system, and therefore a call across the PSTN is required in order to access the coverage point. The coverage path may next include a telephone number for the coverage point. After the telephone number, a second special character is included that signals the remote system to wait for the coverage point to answer the call before proceeding. A third special character may then be provided, that instructs the branch system to transmit the identifier for the called extension to the coverage point, after the coverage point has answered the call. Accordingly, where a number of communication endpoints or extensions associated with a branch use the same coverage point, a coverage path involving that coverage point can be defined using an identical script or coverage path for each of the extensions. 
     In accordance with further embodiments of the present invention, a call coverage routine scripted in accordance with embodiments of the present invention may be used in connection with providing at least limited dial plan transparency. In particular, when a primary network connection between a branch and a central system or another branch system is inoperable, a trunk call to a called party&#39;s direct inward dialing (DID) number can be placed automatically by executing a coverage path that contains special variable characters. In particular, any digits required for access to the PSTN and the area code and prefix of the DID for the called system followed by a special character indicating that the number of the called extension is to be entered, can be provided as a call coverage path script. In accordance with other embodiments of the present invention, where the branch system associated with the calling extension is in a survivable processor mode, a trunk call to a remote access number is generated in response to receiving digits comprising an extension on another branch. After the communication server associated with the called extension has answered the trunk call, the called party&#39;s extension number is automatically provided. Accordingly, calls between branches can be completed even if primary network connections are inoperable, without requiring that the caller enter the complete DID number for the called party, and without requiring a unique coverage script for each extension in each branch. 
     Additional features and advantages of embodiments of the present invention will become more readily apparent from the following discussion, particularly when taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram depicting components of a system in accordance with embodiments of the present invention; 
         FIG. 2  is a block diagram depicting components of a communication server in accordance with embodiments of the present invention; 
         FIG. 3  is a flow chart illustrating aspects of the operation of a system in accordance with embodiments of the present invention; and 
         FIG. 4  is a flow chart illustrating other aspects of the operation of a system in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to providing at least partial dial plan transparency and/or to facilitating call coverage in connection with distributed private branch exchange systems during survivable processor operation. As used herein, survivable processor operation occurs when a primary network connection between a branch system of a distributed private branch exchange system and another branch system or a central system is inoperable. 
     With reference to  FIG. 1 , components of a distributed private branch exchange (PBX) system  100  in accordance with embodiments of the present invention are shown in block diagram form. In particular, the distributed PBX system  100  includes a main server  104  associated with a main database  108 . The main server  104  and associated main database  108  are interconnected to a first local area network  112   a . The first local area network  112   a  is additionally interconnected to a gateway  116  that may incorporate or be interconnected to a communication feature server  120 , such as a voice mail server. Alternatively, a communication feature server  120  may be directly interconnected to the first local area network  112   a . Together, the main server  104 , main database  108 , first local area network  112   a , gateway  116  and communication feature server  120  comprise a main or central system or region  124 . The main or central system  124  is part of a distributed private branch exchange (PBX). Accordingly, the main system  124  may be interconnected to a branch system or region  132  by a first or primary network connection  128 , such as a wide area network. Furthermore, as used herein a main system  124  may comprise all the attributes of a branch system  132 , and therefore comprises a special type of branch system  132 , with additional features, such as a central communication feature server  120 . 
     The branch system  132  may include a remote branch server  136  that includes or is associated with a copy of the main database  140 . The main database  108  and/or the copy of the main database  140  may comprise menus for storing call coverage information. The branch system  132  may additionally comprise a second local area network  112   b  for interconnecting various components included in the branch system  132 . The branch system  132  may also include a gateway  144  and a number of communication endpoints  122 . The communication endpoints  122  may be directly connected to the local area network  112   b , or to the local area network  112   b  through other components, such as through the branch gateway  144 . 
     The main server  104  and remote branch server  136  generally function to provide telephony features for and control of components associated with their respective systems  124 ,  132 . Accordingly, a main server  104  or branch server  136  can comprise means for controlling aspects of the operation of means for communicating. The functions performed by the main server  104  or branch server  136  can include call coverage operations. Call coverage operations generally take effect when an extension comprising or associated with a communication endpoint  122  or a feature provided by a communication feature server  120  does not answer a call. In addition, in accordance with embodiments of the present invention, call coverage functions can be applied to connect a caller dialing from an extension  122  within the system  100  to another extension  122  within the distributed PBX system  100  even if a primary network  128  (e.g. wide area network) connectivity is unavailable, and without requiring the caller to manually enter the complete telephone number of the called extension in order to route that extension across the PSTN  148 . In accordance with embodiments of the present invention, the main server  104  and branch server  136  may comprise private branch exchange or communication servers. 
     The main data base  108  associated with the main server  104  generally functions as a central repository for information related to the distributed PBX system  100 . Such information may include system extensions and direct inward dialing (DID) numbers for communication endpoints  122  associated with the distributed PBX system  100 . In addition, the main data base  108  may function as a central repository for coverage paths associated with communication endpoints  122  or telephony features and that are included in the distributed PBX system  100 . In accordance with embodiments of the present invention, a coverage path defined for a communication endpoint  122  associated with a branch system  132  will include at least a first call coverage routine or path for use during normal operation of the distributed PBX system  100  and a second call coverage routine or path for use where the primary network connection between the branch system  132  and the main system  124  is inoperable. 
     The main gateway  116  and branch gateway  144  generally interconnect their associated region or system  124  or  132  to the PSTN  148 . Therefore, a gateway  116 ,  144  may comprise a means for interconnecting to a second communication network means. For example, each gateway  116 ,  144  may interconnect to the PSTN  148  via a trunk line. As a result, calls from outside the distributed PBX system  100  can be placed to extension associated with the main system  124  through the main gateway  116  or to extensions associated with the branch system  132  through the branch gateway  144 . In addition, via the gateways  116 ,  144 , calls can be placed between the main  124  and branch  132  systems across the PSTN  148 . Network devices, such as communication feature servers  120  and communication endpoints  122 , can also sit off or be associated with a gateway  116 ,  144 . Furthermore, while the functions of a gateway  116 ,  144  are typically considered separately from the functions of other devices within a region, a physical switch or server implementing a gateway  116 ,  144  may also implement other devices, such as a main server  104 , remote branch server  136  and/or communication feature server  120 . 
     A communication feature server  120  can provide features or services in connection with the system  100 . For example, a communication feature server  120  may comprise a voice mail server, interactive voice response (IVR) server, and/or a customer relationship management (CRM) server. Accordingly a communication feature server may comprise a means for providing communication features. 
     A communication endpoint  122  is generally associated with an extension. For example, an extension can identify each communication endpoint  122  within the distributed PBX system  100  comprising the main system  124  and all of the branch systems  132 . A communication endpoint or means for communicating  122  may comprise a telephone, an Internet protocol telephone, a soft telephone implemented in connection with a general purpose computer, a portable computing and/or communication device, such as a personal digital assistant, or any other wire line or wireless device associated with an extension within the main system  124  or branch system  132  of a distributed PBX system  100 . 
     During normal operation, calls received at the main system  124  or the branch system  132  that are directed to a communication endpoint  122  have access to a communication feature server  120  operating within the main branch  124  for coverage operations. Furthermore, when an incoming call is received at a branch gateway  144  for a communication endpoint  122  associated with a branch system  132 , the communication feature server  120  may be accessed across a primary network or first communication network means  128  Internet protocol connection between the main system  124  and the branch system  132 . Such operations may include coverage operations that are implemented if the communication endpoint  122  is not answered by a user. In general, coverage paths for communication endpoints  122  are stored in the main database  108 , with copies of the main database  140  distributed to each branch system  132 . This communication may be formed through means for interconnecting comprising a connection between a node on the LAN  112  and the first network  128 . 
     If the primary network  128  connection between the main system  124  and the branch system  132  is severed or inoperable, the branch system  132 , and in particular the branch server  136 , operates in survivable processor mode. In survivable processor mode, the branch server  136  controls functions associated with the branch system  132 . Because the branch server  136  has access to a copy of the main database  140 , most of the functions of the system  100  can operate normally. However, because there is typically only one communication feature server  120  provided as part of the main system  124  for certain features, calls that require coverage from that communication feature server  120  must be routed from the branch system  132  to the main system  124  over the PSTN  148  when the IP protocol link is inoperative. In prior art systems, routing a call across the PSTN  148  to access a coverage point comprising a voice mail server or other feature that depended on or could benefit from an identification of the called communication endpoint  122  would result in a request to the calling party to provide an identification of the called communication endpoint  122 . For example, when the communication feature server  120  provides a voice mail function, the calling party would have to normally enter the extension of the communication endpoint  122  that was being called in order to access the voice mailbox for that extension. After being provided with the identification information, the communication feature server  120  could then play back a personalized greeting associated with the called communication endpoint  122 . As described herein, embodiments of the present invention provide for the delivery of information identifying a called communication endpoint  122  without requiring manual input from a caller, and without requiring the administration of a unique coverage path for each communication endpoint  122  using a communication feature server  120  or other component or node that requires information identifying the called extension as a coverage point. 
     With reference now to  FIG. 2 , the components of a main server  104  or a remote branch server  136  implementing some or all of the coverage path application features described herein in accordance with embodiments of the present invention are depicted in block diagram form. The components may include a processor  204  capable of executing program instructions. Accordingly, the processor  204  may include any general purpose programmable processor, digital signal processor (DSP) or controller for executing application programming. Alternatively, the processor  204  may comprise a specially configured application specific integrated circuit (ASIC). A processor  204  generally functions to run programming code implementing various functions performed by the server  104 ,  136 , including telephony support applications and coverage path applications as described herein. 
     A server  104 ,  136  may additionally include memory  208  for use in connection with the execution of programming by the processor  204  and for the temporary or long-term storage of data or program instructions. The memory  208  may comprise solid state memory resident, removable or remote in nature, such as DRAM and SDRAM. Where the processor  204  comprises a controller, the memory  208  may be integral to the processor  204 . 
     In addition, the server  104 ,  136  may include one or more user inputs or means for receiving user input  212  and one or more user outputs or means for outputting  216 . Examples of user inputs  212  include keyboards, keypads, touch screens, touch pads and microphones. Examples of user outputs  216  include speakers, display screens (including touch screen displays) and indicator lights. Furthermore, it can be appreciated by one of skill in the art that the user input  212  may be combined or operated in conjunction with the user output  216 . An example of such an integrated user input  212  and user output  216  is a touch screen display that can both present visual information to a user and receive input selections from the user. In accordance with embodiments of the present inventions, a user input  212  and user output  216  associated with the server  104 ,  136  may be used by an administrator in connection with creating or loading coverage path instructions and other information related to the operation of a private branch exchange main system  124  or branch system  132 . 
     A server  104 ,  132  may also include data storage  220  for the storage of application programming and/or data. Furthermore, in accordance with embodiments of the present invention, the data storage  220  may, in the case of a main server  104 , comprise all or part of the main database  108 , and in connection with a branch server  136 , the data storage  220  may comprise all or part of that branch system&#39;s  132  copy of the main database  140 . Accordingly, the data storage  220  may store coverage paths  224  for communication endpoints  122  or other addressable devices included in a distributed PBX system  100  in accordance with embodiments of the present invention. In addition, various telephony support applications  228 , such as a coverage path application  232  may be stored in data storage  228 . Operating system software  236  may also be stored in the data storage  220 . The date storage  220  may comprise, for example, a magnetic storage device, a solid state storage device, an optical storage device, a logic circuit, or any combination of any such devices. It should further be appreciated that the programs and data that may be maintained in the data storage  220  can comprise software, firmware, or hardware logic, depending on the particular implementation of the data storage  220 . 
     A server  104 ,  136  may also include an Internet protocol (IP) network interface  240 . An example of an IP interface  240  is a network interface card (NIC). In connection with a server  104 ,  136  that also implements a gateway  116 ,  144 , a public switched telephony network (PSTN) interface  244  may also be provided. 
     With reference now to  FIG. 3 , aspects of the operation of a private branch exchange  100  in accordance with embodiments of the present invention are illustrated. Initially, at step  304 , an incoming call is received that is directed to an extension associated with a branch system  132 . For example, a call may be received from the PSTN  148  at the branch gateway  144 . 
     A determination may then be made as to whether the incoming call has been answered at the called extension (step  308 ). If the call is answered, the process may end. If the call is not answered at the called extension, the branch server  136  may access a coverage path for the called extension to determine where to direct the call. 
     As part of determining how to route the incoming call, the branch server  136  may determine whether it is operating in survivable processor mode. In particular, embodiments of the present invention provide different coverage paths depending on whether the private branch exchange system  100  is operating normally, or whether a branch system  132  receiving a call requiring coverage is not connected to the main system  124  by the primary network  128 , and therefore is operating in survivable processor mode (step  312 ). If the primary network  128  connection interconnecting the main system  124  to the remote system  132  is available, the branch server  136  will apply coverage paths specified for normal operation in sequence, until coverage for the call is obtained. In so doing, the call may be routed from the branch system  132  to a coverage point, such as a communication feature server  120  (e.g. a voice mail server) associated with the main system  124  normally, across the primary network  128  connection, and the communication feature server  120  can handle the call normally (step  316 ). In particular, information regarding the called extension can be passed across the primary network  128  connection to the communication feature server  120 , allowing the communication feature server  120  to play back a personalized greeting associated with the called extension or otherwise apply features or messages associated with the called extension. After connecting the call to a coverage point across the primary network connection  128 , the process may end. If it is determined at step  312  that the branch system  132  is operating in survivable processor mode, then those coverage paths indicated as being for use while the branch system  132  is in survivable processor mode are applied (step  318 ). 
     In general, because survivable processor mode is entered while a primary network  128  connection between the branch system  132  and the main system  124  is inoperable, coverage paths applied while in such a mode involve calls placed across the PSTN  148 . Accordingly, applying a survivable processor mode coverage path involves connecting to a coverage point over the PSTN  148  (step  320 ). Connecting to a coverage point over the PSTN generally comprises dialing the complete direct inward dialing (DID) number for the coverage point from the branch gateway  144 , to establish a connection with a coverage point, such as a communication feature server  120  or another extension  122  through the PSTN  143  and the main gateway  116 . At step  324 , a determination is made as to whether an answer has been received from the coverage point. In general, the branch server  136  will wait for at least a predetermined period of time for the coverage point to answer. If no answer is received after that predetermined period of time has elapsed, a next coverage path may be applied (step  328 ), if available. 
     After receiving an answer from a coverage point at step  324 , the branch server  136  transmits the identifier for the called extension (e.g. the extension associated with the called endpoint  122 ) to the coverage point (step  332 ). The call is then handled by the coverage point through the PSTN  148  connection as if the call had been forwarded to the coverage point across the primary network  128  connection (step  336 ). That is, by providing the called extension to the coverage point automatically, embodiments of the present invention allow calls sent to coverage during survivable processor operation to appear to the calling party as if they were handled normally. In addition, the present invention permits such apparently seamless handling of calls sent to coverage during survivable processor operation, without requiring the creation of a unique call coverage path for each extension associated with a branch system  132 . 
     In particular, special characters are defined that permit a single coverage path script to be used in connection with any number of extensions in a branch system  132  and a common coverage point, such as a communication feature server  120  associated with the main system  124 , while the branch system  132  is in survivable processor mode. These characters may include an initial character that indicates to a coverage path application  232  running on the branch server  136  that the coverage path is only for use during survivable processor operation. Providing this indication prevents the branch server  136  from placing calls across the PSTN  148  when the IP network connection  128  is available. Next, the script may include the direct inward dialing (DID) number for the target coverage point. The direct inward dialing number may be pre-pended by any digits necessary to successfully dial across the PSTN  148  between the branch system  132  and the main system  124 . For example, the number may include a nine, to indicate to the branch gateway  144  that the call is to be placed across the PSTN  148 . In addition, the DID number of the target coverage point may be pre-pended by a one if the call across the PSTN  148  is long distance. The remainder of the number will typically be the 10 digit telephone number for the coverage point. After the digits required to access the coverage point across the PSTN  148 , the coverage path script may include a special character to indicate that the branch server  136  should wait for an answer from the target coverage point before continuing with execution of the script. Finally, another special character may be included that instructs the branch server  136  to transmit the called extension number to the coverage point across the PSTN  148 . 
     Accordingly, an example of a called coverage path script for use during survivable processor operation is as follows: L912225387999% D, where L is the special character indicating that the coverage path script is for application only during survivable processor operation, the following number is comprised of any digits that must be dialed in order to access the target coverage point across the PSTN  148 , the percent symbol directs the branch system server  136  to wait for a response from the target coverage point before executing the remainder of the script, and D is the special character directing the branch system server  136  to provide the called extension number to the coverage point after the coverage point has answered the call. The particular characters chosen to operate as special characters as described herein can generally be any character not already assigned to other functions that can be executed as part of a coverage path script. In accordance with embodiments of the present invention, the special characters chosen for a particular purpose may serve a mnemonic function. For example, the choice of L can suggest Local survivable processor operation, while the choice of D can suggest the calleD party extension. 
     Each extension that shares a coverage point can share the same coverage path script for use during survivable processor operation. Furthermore, by the use of special characters as described herein, the coverage path for use during survivable processor operation provides for the identification of the called extension to the coverage point, allowing the coverage point to respond as appropriate for the called extension. Furthermore, the identification of the called extension to the coverage point is accomplished without requiring manual input from a calling party. In addition, the use of special characters as described herein in the coverage path avoids the need to administer a unique coverage path script for use during survivable processor operation for each extension. 
     Although certain examples provided in the present description have discussed transferring a call placed to an extension that does not answer to a coverage point comprising a communication feature server  120 , such as a voice mail server, even during survivable processor operation, embodiments of the present invention are not so limited. For instance, dial plan transparency can be provided for calls between extensions or within a branch system. For example, dial plan transparency or PSTN coverage can be provided for calls between extensions on the same branch system  132 , or between a branch system  132  and the main system  124 . More particularly, rather than dialing a coverage point, a remote access number for the called extension&#39;s system  124 ,  132  can be dialed as directed by a call coverage path. After an answer is received, a special character in the call coverage path signals the calling branch server  136  to provide the extension number of the called extension, allowing the call to be completed, without requiring that the calling user enter (or re-enter) the called extension and without requiring a unique script for each extension accessible through a common remote access number. 
     With reference to  FIG. 4 , other aspects of the operation of a distributed private branch exchange system  100  in accordance with embodiments of the present invention are illustrated. In step  400 , a call is placed from a first extension in a first region  132  of a distributed private branch exchange system  100  to a second extension in a second region  124  of the distributed private branch exchange system  100 . At step  408 , a determination is made as to whether the primary network  128  connection between the regions  124 ,  132  is available. If the connection across the primary network  128  between the regions  124 ,  132  is available, a connection between the first and second extensions is established normally (step  412 ). That is, by entering only those digits of the called extension, the call can be established. 
     If the primary network  128  connection between the regions  124 ,  132  is not available, the coverage path for the called extension is referenced, and a call to the called extension is executed over the PSTN  148  (step  416 ). That is, the coverage path for the called extension comprises a script that results in a call being placed between the regions  124 ,  132  using the 10-digit number of the called extension. Furthermore, the call across the PSTN  148  is accomplished without requiring manual input from the calling party. Instead, the 10-digit number is dialed in response to the coverage path script. Furthermore, the coverage path script can include any initial digits that must be dialed, such as a “9” indicating that the call is to be placed across the PSTN  148 , and a “1” if the call across the PSTN  148  is long-distance, and the area code for extensions associated with the called region. The prefix (e.g., 2 or 3 digits) for extensions associated with the called region can then be specified by the path, followed by a special character signaling that the called extension (e.g., 4 or 5 digits) should be dialed. Accordingly, as can be appreciated by one of skill in the art from the description provided herein, the same coverage path script can be used for every extension in a region  124 ,  132  of a distributed private branch exchange system  100  having the same area code and prefix. As a result, a call between extensions in different regions  124 ,  132  can appear as if it was completed normally, even during an outage of the network connection  128  that is normally used, without requiring the administration of a unique coverage path script for each extension in the distributed PBX system  100 . 
     In accordance with embodiments of the present invention, individual extensions may be associated with a number of coverage paths. For example, a typical extension may have three coverage paths: (1) a coverage path that causes the DID number of the called extension to be dialed for use during an outage of the primary network  128  connection between regions for calls placed to an extension from an extension associated with another region of the distributed PBX system  100 ; (2) a path to a communication feature server  120  comprising a voice mail server for use during normal operation; and (3) a path used during an outage of the primary network  128  between a branch region  132  and the main region  124  that places a call across the PSTN  148  to the server  120  and that automatically provides the called extension to the server  120 . In accordance with embodiments of the present invention, where all three of these example coverage paths are provided, the first coverage path script need not be executed in connection with an extension associated with a branch  132  if the branch server  136 , or if the branch server  136  recognizes that the called extension is part of the branch server&#39;s  136  region  132 . In accordance with still other embodiments of the present invention, an additional special character may be defined to distinguish between coverage path scripts that are to be executed when the primary network  128  connection is unavailable and a call needs to be forwarded to a coverage point across the PSTN  148 , and coverage path scripts that are to be executed when the primary network  128  connection is unavailable and a call must be placed across the PSTN  148  in order to establish a connection between extensions in different branches  124 ,  132  of the distributed PBX system  100 . 
     Although exemplary embodiments of the present invention have been discussed in the context of a central or main region  124  in association with a single branch region  132 , it should be appreciated that other arrangements can be provided. For example, a distributed PBX system  100  can comprise a number of branch regions  132 . In addition, although examples have described a primary network  128  as comprising a wide area network, connections between regions  124 ,  132  can be by other means. For example, any type of Internet protocol network or combination of networks may comprise a primary network  128 . 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. Further, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, within the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain the best mode presently known of practicing the invention and to enable others skilled in the art to utilize the invention in such or in other embodiments and with the various modifications required by their particular applicational use of the invention. It is intended that the impended claims be construed to include alternative embodiments to the extent permitted by the prior art.