Abstract:
A switch proxy comprising a controller, a translations database and a switching fabric are connected to a trunk group between a remote terminal and its controlling local switching system. The switch proxy monitors control signals to and from the switching system on the trunk. In the event of loss of control signals from the host switching system, the switch proxy intercepts requests for service, etc. from a calling telephone connected to the remote terminal and performs a look up in the translation database. If the call can be completed without the controlling switching system the call is looped back to the remote terminal. The translation database is maintained by a switch proxy management system that receives change orders from the local exchange carrier. The switch proxy management system forwards relevant changes to the switch proxy&#39;s translation database in the field.

Description:
[0001]     This patent application claims the benefit of U.S. provisional patent 60/625,911, filed Nov. 8, 2004, and entitled “Method for providing emergency stand alone service for digital loop carrier systems”. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to access systems as used in wireline telephony, and, more specifically, to a switch proxy for use in conjunction with an access system remote terminal to route telephone calls when communications between a remote terminal of an access system and its controlling switching system is lost.  
         [0003]     Wireline telephone service providers use access systems (such as, but not limited to, subscriber loop carriers and digital loop carriers) to serve telephone subscribers that are not economically or practically served directly from the nearest local switching system. An access system consists of a remote terminal that is connected to a local switching system by one or more digital trunk groups. These trunk groups contain a multiplicity of digital channels for carrying the voice traffic and separate digital channels for control information between the switching system and the remote terminal. The local switching system controls the remote terminal as if it were an extension of the switching system. In the usual case, a remote terminal provides digital connectivity between the remote telephone subscribers and the host switching system and does not participate in the routing of calls. In this manner, service providers are afforded more options in providing telephone service to subscribers; in particular, these access systems provide a much more economical approach to serve a small remote community of subscribers than the use of expensive local switching systems or proprietary remote switching modules.  
         [0004]     The simplicity of aggregating all of the call control functionality in the host switching system creates a problem in the art. That is, when the host switching system is unable to communicate with the remote terminal, either through failure of components of the digital trunks or of the switching system itself, subscribers served by the remote terminal no longer have any telephone service. Even though the connectivity with the greater network is lost and the remote terminal may be otherwise fully functional, the subscribers terminated on this remote system still cannot communicate with one another. The severity of this problem may be confounded by the fact that these subscribers are frequently served by this technology precisely because they are remote; these remote settings necessitate the use of local emergency responders and limit other communications options (e.g, cellular telephony). Therefore, the ability to continue to locally switch calls between subscribers served by remote systems that have lost communications with a host switching system is an important public safety consideration.  
         [0005]     While manufacturers of access systems are currently considering the incorporation of so-called “emergency stand alone” service into their next generation of product, this does nothing to address the provision of this capability to the vast majority of access systems which are currently in use and are otherwise fit for service. Other suggestions in the art pertain to installation of a “miniature” switching system in the proximity of the remote terminal to serve as a local host. This approach is not only expensive but impractical on several counts: 
        i) it changes the basic architecture of the exchange network,     ii) it increases the number of switches to administer and maintain,     iii) it actually increases the probability of a service outage by putting another switching system into the chain, and     iv) these remote terminals are frequently installed in field cabinets where it may be impossible to install an additional complex system. 
 
 Thus there currently does not exist an economical or practical scheme for providing emergency stand alone service to subscribers served by the installed base of access systems. 
       
 
       SUMMARY OF THE INVENTION  
       [0010]     This problem is solved and a technical advance is achieved in the art by a system and method that provides a switch proxy apparatus to control one or more remote terminals when connection to a host switching system is lost. A switch proxy in accordance with this invention comprises a controller, a translations database and a switching fabric, which are connected to the trunk group between the remote terminals and the local switching system. The controller, translations database and switching fabric are so adapted and configured that: a translations database maintains translations for its associated remote terminal and the switching fabric has a capacity to switch calls among subscribers served by that switch proxy and its subtended remote terminals. Thus, no modification of existing infrastructure, either in the switching system or the remote terminal, is needed, except to introduce this switch proxy in the trunk group between the local switching system and the remote terminal. Indeed, neither the host switching system nor the remote terminal need be aware of the existence of this switch proxy for proper operation.  
         [0011]     In accordance with one aspect of this invention, the switch proxy monitors control signals on the trunk group between the remote terminal and its controlling switching system. In the event of loss of communication of control signals on the trunk group, the switch proxy seizes control of all or a subset of the trunk group and re-establishes the interface with the remote terminal with itself as the “host switching system” thereby becoming the proxy for the actual host system. To the remote terminal, it appears as though a short outage with the switching system has occurred followed by restoration of some or all of the services from the switching system. The switch proxy intercepts requests for service, etc., from a calling telephone connected to the remote terminal and performs a look up in the translation database. If the call can be completed within the isolated remote system (i.e., the call is for a telephone also connected to the remote terminal or another subtended remote terminal), the controller of the switch proxy causes the switching fabric to loop the call back to the remote terminal and the causes the remote terminal to perform ringing and other such functions as required to establish the call. The switch proxy continues to monitor the transmission links towards the host switching system and when it ascertains that stable communications with that system have been restored, it initiates the process of dropping calls that it is carrying and reverts to monitoring, thus allowing the host switching system to resume providing service to the remote terminal. The switch proxy again takes up the role of monitoring the trunk group between the host switching system and the remote terminal.  
         [0012]     Importantly, the switch proxy&#39;s translation database is maintained by a switch proxy management system, this translation database as a minimum maintains correspondence between a telephone subscriber&#39;s physical appearance (port address) on the remote terminal and its telephone number. Advantageously, as subscribers are rearranged by the telephone service provider, change orders for several remote terminals may be received and processed by the same switch proxy management system. The switch proxy management system forwards relevant changes to each switch proxy&#39;s translation database. Further, maintenance and updates to the switch proxy itself may be made in the same fashion. In this manner, a low-cost switch proxy may be used to maintain telephone service on a remote terminal when the remote terminal is disconnected from its host switching system.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     A more complete understanding of this invention may be obtained from a consideration of this specification taken in conjunction with the drawings, in which:  
         [0014]      FIG. 1  is a block diagram of a wireline telephone system in which an exemplary embodiment of this invention is implemented;  
         [0015]      FIG. 2  is a block diagram expanding on the details of  FIG. 1 ;  
         [0016]      FIG. 3  is a block diagram of an exemplary embodiment of the switch proxy of  FIG. 1  and  FIG. 2 ;  
         [0017]      FIG. 4  is a block diagram illustrating the operational modes of a switch proxy;  
         [0018]      FIG. 5  is a flow chart describing an exemplary embodiment of the control functions of a switch proxy of  FIG. 3 ;  
         [0019]      FIG. 6  is a flow chart describing an exemplary embodiment of call processing functions of a switch proxy;  
         [0020]      FIG. 7  is a block diagram illustrating the functional components of a switch proxy management system; and  
         [0021]      FIG. 8  is a flow chart illustrating the operation of the switch proxy management system of  FIG. 7 . 
     
    
     DETAILED DESCRIPTION  
       [0022]      FIG. 1  is a block diagram of a wireline local telephone network  100  in which an exemplary embodiment of this invention operates. In the wireline local telephone network  100  of  FIG. 1 , a local switching system  102  (also referred to herein as local switch  102  or switching system  102 ), typically residing in a central office  104  is connected through trunk group  106  to the public switched telephone network (PSTN)  108  which provides for interconnectivity with subscribers worldwide. This configuration is used herein for convenience and clarity in describing the invention; it is well known in the art that local switching system  102  is part of PSTN  108 . A plurality of telephone subscribers  110 ,  112  may be connected directly to the local switching system through subscriber lines. Additionally, a plurality of subscribers  114 ,  116 ,  118 , and  120  may be supported from remote terminals  122  and  124  which interconnect to the local switch through trunk groups  126  and  128  respectively. In the present context, a trunk group (also referred to herein as a trunk or trunks) consists of one or more physical transmission media (e.g., fiber optical cables or T1 lines) transporting a multiplicity of digital channels between network elements such as, but not limited to, trunk group  126  between local switching system  102  and remote terminal  122 . In general, remote terminals  122  and  124  consolidate and concentrate signals to and from the customer telephones  114 ,  116 ,  118 , and  120  and connect these distant telephone subscribers to the local switch  102  over trunks  126  and  128  that have a capacity to support many voice and data channels over long distances. Such access system remote terminals as  122  and  124  are also known in the art as subscriber loop carriers (“SLCs”) and digital loop carriers (“DLCs”) and functionally referred to as remote terminals. In accordance with this invention, a switch proxy  130  (illustrated herein in heavy block line and described in more detail in conjunction with  FIG. 3 ) residing logically between the remote terminal  124  and the trunk  128  maintains telephone services between subscribers  118  and  120  served by remote terminal  124  when communications with local switch  102  is lost, for whatever reason. In this manner, some basic services that formerly were not provided when remote terminal  124  was isolated from local switching system  102  are now available. For illustration purposes, assume that remote terminal  124  provides service to a rural community many miles from local switching system  102 . Further, assume that telephone  120  is a telephone at a local public safety provider, such as (but not limited to) a local fire department or county sheriff&#39;s office. In the prior art, should communications with the local switch fail, a caller at telephone  118  could not contact telephone  120  in an emergency, even though both telephones are in the same community and the remote terminal is fully functional. In accordance with this invention, switch proxy  130  takes over during an outage and provides at least limited local service. Thus, telephone  118  can be connected to telephone  120  in accordance with this invention, even when local switching system  102  cannot provide service.  
         [0023]      FIG. 2  further illustrates some interface details of subscribers  110  and  112  supported directly from switch  102 , and subscribers  114 ,  116 ,  118  and  120  deployed behind remote terminals  122  and  124  hosted by local switch  102 . Local switch  102  contains a switching fabric  202  that interconnects, on a channel-by-channel basis, a plurality of line units, herein represented by line units  204  and  206  and trunk units, herein represented by trunk unit  208 . These trunk and line unit subsystems serve to adapt the circuits useful to the network, such as telephone lines, to a format that can be switched by switching fabric  202 . Switching system  102 , as is well known in the art, provides many other functions such as billing and operator services, etc., which do not contribute to the understanding of this invention and are thus not described. Switching fabric  202 , line units  204 ,  206  and trunk unit  208  are all well known in the art, do not form part of the invention and thus are not further described.  
         [0024]     A control unit  210  causes switching fabric  202  to connect a particular line (or member of a trunk group) to another based on information contained in translations database  212  which associates an internal physical port address to a designation useful to the network, such as, a telephone number. When interfacing to access systems a special line unit called an integrated digital terminal (“IDT”)  214  can be used to interface directly with digital trunks  126  to communicate with and control remote terminal  122 . An alternative approach is represented by the use of a central office terminal  216  to convert a plurality of subscriber lines originating on line unit  206  into a multiplexed digital signal carried by digital trunk  128  that communicates to the remote terminal  124 . One skilled in the art will appreciate that the control signals embedded in trunks  126  and  128  must provide similar services and may, in fact, be identical regardless of the methodology (e.g., integrated digital terminal  214  or central office terminal  216 ) used to interface to switch  102 . These cases illustrate that the subscriber lines deployed using access systems do not differ significantly from those supported directly from switch line units in that they rely on the local switch for dialed digit collection, switching, translation, and other services.  
         [0025]     As is standard in the art, control unit  210  of local switch  102  controls all remote terminals (herein  122  and  124 ). Thus, when a telephone (such as telephone  114 ) goes off-hook, remote terminal  122  detects the off-hook condition and reports the off-hook condition to integrated digital terminal  214 . Integrated digital terminal  214  forwards the information to control unit  210 . Control unit  210  causes switching fabric  202  to provide dial tone through integrated digital terminal  214 , digital trunk  126  and remote terminal  122  to telephone  114 . Telephone  114  then sends dual-tone, multifrequency signals (or dial pulses) back to control unit  210 , which decodes the signals into dialed digits and performs a look-up in translations database  212  to determine how to handle the call. As is well known in the art, the local switch  102 , by means of controller  210  controls the setup and tear down of all calls, whether originating or terminating on subtended remote terminals  122  and  124 . Signaling protocols are used between the access system remote terminal and the central office components (e.g., remote terminal  122  and integrated digital terminal  214 , and remote terminal  124  and central office terminal  216 , respectively) to coordinate the connection and signal the status of both ends. For example, GR-303 and GR-08, both generic requirements(GR) published by Telcordia, Inc. and well known in the art, are commonly used standards-based signaling protocols for providing telephone service through remote terminals. While some remote terminals (especially older remote terminals) use proprietary protocols, it is within the ability of one skilled in the art to build a switch proxy in accordance with whatever protocol may be used after studying this specification. The signaling uses bandwidth within the trunks interconnecting the remote terminal and the host switch (e.g., trunk  126  connecting host switch  102  and remote terminal  122 ) for messaging to convey status and cause actions, these messaging channels are also referred to as control signals.  
         [0026]      FIG. 3  is a block diagram of switch proxy  130  illustrating certain exemplary aspects of this invention. In general, switch proxy  130  comprises a trunk monitoring unit  314 , a switching fabric  302  interconnected with a trunk interface unit  304  by connections  305  and interconnected with tones and receivers unit  318  by connections  316 , a bypass switch  312 , and a controller  306  which coordinates the operations of all of the subsystems. In this exemplary embodiment, switching fabric  302  comprises a time slot interchange unit. One skilled in the art will appreciate that other types of switching fabrics (e.g., space division solid state or metallic switches) may be employed to the same end.  
         [0027]     In this exemplary embodiment, bypass circuit  310  is connected around the operational units of switch proxy  130 . Bypass circuit  310  includes a normally closed switch  312 . That is, during normal operation of remote terminal  124  under control of local switching system  102 , bypass switch  312  is closed and the switch proxy  130  is logically bypassed until such time as intervention is required. Thus, advantageously, failures within the switch proxy  130  are unlikely to affect normal operation of the remote terminal. A skilled practitioner of the art can suggest other embodiments in which this bypass circuit is not required, such as, but not limited to, passing the traffic actively from trunk  128  to trunk  132  through switch proxy  130 .  
         [0028]     A trunk monitoring unit  314  is connected to trunk  128  in parallel with bypass circuit  310  on the central office terminal  216  side of switch proxy  130 . Trunk monitoring unit  314  monitors trunk  128  for control signals from local switching system  102  and responses from remote terminal  124 . When a service interruption is detected, trunk monitoring unit  314  notifies controller  306  while continuing to monitor trunk  128 . Controller  306  causes switch  312  to open and begins to supervise trunk  132  from remote terminal  124  by means of trunk interface unit  304 . Controller  306  sends and receives control signals to/from telephones connected to remote terminal  124  by means of the control channels embedded in trunks  132  in the same manner as local switch  102  does during normal operation. Based on information in these control signals, controller  306  causes switch fabric  302  to interconnect channels associated with subscribers in trunk  132  with the appropriate tones, dialed digit receivers and/or recorded announcements in tones and receivers unit  318 . After collection of the dialed information either through interpretation of rotary digits or from dual tone multi-frequency digits received by the tones and receivers unit  318 , the controller  306  consults the translation database  308  to determine if the call can be completed within the subscriber base supported by remote terminal  124  or another remote terminal (not shown) served by switch proxy  130 . If the call can be completed, controller  306  causes switching fabric  302  to connect one telephone to another. If it is not possible to route the call (e.g., the subscriber is not served by an remote terminal subtended to switch proxy  130 ) controller  306  causes switching fabric  302  to connect the calling party to an appropriate tone or recorded announcement supplied by tones and receivers unit  318 .  
         [0029]     Controller  306  uses data stored in translation database  308  to provide such information as to determine what connections are possible as well as to provide translations between physical port addresses and telephone numbers. In addition, translation database  308  may contain information that would be useful to emergency responders such as, but not limited to: subscriber name and address, GPS coordinates, and prioritized emergency responders for each subscriber based on location. These data, or a subset thereof, in translation database  308  are synchronized to translation database  212  in local switch  102  regarding telephones connected to remote terminal  124 . Such synchronicity may be provided by a centralized switch proxy management system (which will be described herein, below, in conjunction with  FIG. 7 ) or manually through a local interface to switch proxy  130 . Two exemplary approaches to management of the switch proxy  130  are illustrated in  FIG. 3 : a centralized switch proxy management system  134  is interconnected to the remote switch proxy  130  via communications means  136 ; alternatively, a local terminal  140  (sometimes referred to in the art as a craft terminal) interconnects with the switch proxy  130  through communications means  138 . Communications means  136  and  138  can be, but are not limited to, dial-up modem, Ethernet, or direct serial connection as is well known in the art.  
         [0030]     An overview of the operational modes of switch proxy  130  are illustrated in  FIG. 4  in conjunction with  FIG. 3 . As long as the remote terminal  124  continues to communicate normally with the host switch as determined by trunk monitoring unit  314 , bypass switch  312  remains closed and the controller  306  operates in the bypass and monitoring mode  402  in  FIG. 4 . In this mode, the switch proxy  130  remains vigilant to the operational status of the trunks as shown in decision loop  406  but does not intervene in the control of remote terminal  124 . When trunk monitoring unit  314  concludes that the control signals between the host switch  102  and remote terminal  124  have failed, controller  306  changes state through process  408  to the emergency stand alone mode  404  and takes action to assume control of remote terminal  124 . While the system operates in emergency stand alone mode  404 , trunk monitoring unit  314  continues to monitor the status of trunk group  128  and as indicated by decision loop  412  will remain in emergency stand alone mode  404  as long as trunk group  128  cannot communicate with host switch  102 . While in emergency stand alone mode  404 , controller  306  causes bypass switch  312  to open and asserts control of trunk  132  to remote terminal  124  by means of trunk interface unit  304 . When trunk monitoring unit  314  ascertains that trunk group  128  has returned to operational status, controller  306  through process  410  restores the switch proxy  130  to bypass and monitor mode  402 . One skilled in the art will appreciate that momentary and/or transient behaviors in trunk group  128  should not be cause for switch proxy  130  to transition between operational modes  402  and  404  or vice versa.  
         [0031]      FIG. 5  expands on the details of  FIG. 4  and provides an exemplary embodiment of emergency stand alone operational mode  404 . Processing begins in bypass and monitoring mode  402 . When trunks  128  between the host switch  102  and the remote terminal  124  are no longer functional, decision block  406  passes processing to block  502  where bypass switch  312  is opened and simultaneously in block  504  trunks  128  are conditioned into an alarm state known in the art as “remote alarm indication” to assist in restoring service. In block  506  controller  306  by means of trunk interface unit  304  asserts control of trunks  132  towards remote terminal  124 . In preparation for call processing and using the appropriate signaling protocol (e.g., GR-303) controller  306  in block  508  establishes communications with remote terminal  124  and ascertains and initializes the status (on-hook, off-hook, ringing, etc.) of the subtended subscriber lines through an audit process. Continuing on to block  510  switch proxy  130  now begins to process calls for remote terminal  124  and remains in that mode until such time as service with the host switch  102  has been restored. The status of these trunks is ascertained by interrogating trunk monitoring unit  314  in decision block  512 . At such time as stable service in trunks  128  has been restored, processing transitions to block  514 . In this exemplary embodiment in block  514  the switch proxy does not terminate call processing services until such time as any ongoing “911” calls are completed, optionally this block may be omitted. Processing in block  516  causes trunk interface unit  304  to release trunk  132  (e.g., by entering into a disconnected or high impedance state) in preparation to restoring control to the host switch  102  through trunk  128 . Continuing with block  518 , bypass switch  312  is closed, restoring control of remote terminal  124  to host switch  102  and subsequently switch proxy  130  returns to bypass and monitoring mode  402 .  
         [0032]      FIG. 6  expands upon the details of  FIG. 5  and provides an exemplary embodiment of the call processing block  510 . For simplicity and as is common in the art, subscriber lines which originate a call are referred to as “calling” parties and those subscriber lines to which a call is placed are referred to as “called” parties. As described in the foregoing discussion of  FIG. 5 , call processing block  510  is evoked after establishment of the control of remote terminal  124  in the emergency stand alone mode  404 . Beginning with block  602  wherein the controller  306  awaits a control message from remote terminal  124  through trunk interface unit  304  that a subscriber served by remote terminal  124  has gone off-hook and therefore requires service. In the case of a concentrating protocol (e.g., GR-303) switch proxy  130  then sends a control message to remote terminal  124  allocating a time slot on trunk  132  for the calling (off-hook) subscriber to use. In block  604  controller  306  connects the time slot allocated in the previous step to tones and receivers unit  318  by means of switching fabric  302  whereby calling party receives dial tone and has a digit receiver (both for rotary dialing and dual tone multi-frequency dialing, known in the art as an “originating register”) provided. After a proscribed number of dialed digits have been collected, processing moves to block  606  whereupon controller  306  interrogates translations database  308  as to the status of the called party as represented by the dialed number. For the purposes of this discussion decision block  608  interprets the status of called party in one of three ways, to whit: that called party is on remote terminal  124  or other system (not shown) served by switch proxy  130 , called party is not on a served system, or that called party is 911. These three conditions require distinctive processing. One skilled in the art will understand that dial plans can be more complex than in the aforementioned exemplary embodiment and can be accommodated within the context of this invention.  
         [0033]     Continuing on after decision block  608 , should the called party not be a subscriber served by switch proxy  130  (i.e., “off system”) processing passes to block  610  whereby controller  306  causes an appropriate call-progress tone (e.g., “fast busy”) or recorded announcement from tones and receiver unit  318  to be connected to the calling party through switching fabric  302 . After the calling party returns to on-hook or after a suitable time the call is cleared in block  612 . If decision block  608  confirms that the called party is served by switch proxy  130  (i.e., “on system”), processing is passed to block  614  whereupon the call is classified as a “normal call” (i.e., not a 911 call) for the duration of the call.  
         [0034]     Finally, if the result of decision block  608  is that the called party is 9-1-1, processing is passed to block  616  whereupon the call is classified as a “911 call” and afforded special treatment for the duration of the call. Connection with the public safety answering point (“PSAP”), as would be the case when functional communications exists between remote terminal  124  and host switch  102 , is not possible. In accordance with another aspect of this invention, translations database  308  contains one or more “911 designees”, such as a sheriff&#39;s office or fire department, which may be advantageously associated with a specific calling party in order of preference. For example, the preferred 911 designee for a given calling party may be the one that is nearest in proximity. Initially the preferential 911 designee for this calling party is selected as the called party, should processing return to block  616  as a result of a failure to complete this call, successive 911 designees are chosen and the call attempt is repeated. One skilled in the art will appreciate that many alternatives to this exemplary method of selecting alternative 911 designees to optimize the response to calling party are possible. For example, all of the 911 designees could be simultaneous called and the first to answer assigned the call.  
         [0035]     Whether a “normal” or “911 call”, processing will transfer to block  618 . Controller  306  communicates through trunk interface unit  304  to remote terminal  124  the port address of the called party, obtained in blocks  606  or  616  from translations database  308 , and allocates a second time slot on trunk  132  for the called party and communicates this with remote terminal  124 . Communications between controller  306  and remote terminal  124  utilize control signals embedded in trunk  132  and the applicable signaling protocol. Simultaneously remote terminal  124  is caused to initiate ringing on the called party&#39;s line. Controller  306  causes switching fabric  302  to connect the calling party time slot to an “audible ringing” tone via tones and receivers unit  318 . Also in accordance with another aspect of this invention, special ringing patterns and caller ID messages may be sent to the called party in the event of a “911” call to advantageously alert the 911 designee as to the nature of the call.  
         [0036]     In block  620 , if remote terminal  124  alerts switch proxy  130  that the called party has answered, controller  306  causes switching fabric  302  to interconnect the calling and called party time slots completing a voice path as shown in block  622  in which state the call remains until a disconnect event. If after a suitable time the called party has not answered or it has been determined that the called party is already engaged in another call, processing is passed from block  620  to block  624 . Processing is passed back to block  616  in the event of a “911 call” otherwise to block  626  where “busy” tone or “reorder” tone is played to the calling party in the same manner as “audible ringing” tone, described in conjunction with block  618 . After the calling party status, as signaled by remote terminal  124 , returns to on-hook or after suitable time out the call is cleared through block  612 .  
         [0037]     The clearing of a stable call, represented by block  622 , is addressed in block  628  and requires particular attention in this exemplary embodiment in that it is advantageous to treat disconnection of “normal calls” and “911 calls” differently. Whereas it is acceptable to clear stable calls of the “normal” type whenever either party returns to an on-hook state; control of the disconnection of a “911 call” should, at least optionally, be the sole prerogative of the called party. That is, should the calling party in a “911 call” prematurely go on-hook it is desirable the calling party be able to return to off-hook and continue the conversation with the 911 designee until such time as the called party goes to an on-hook state. This is known in the art as “called party control”.  
         [0038]      FIG. 7  is a block diagram of an exemplary embodiment of a switch proxy management system  134  in accordance with another aspect of this invention. This switch proxy management system  134  generally comprises a database  704  and a communications unit (or units)  706  responsive to processor  702 . At least one file is kept for each switch proxy in database  704 , wherein translations records for each line (such as lines  118  and  120 ) served by a switch proxy  130  are maintained. At a minimum, these records correlate the physical port address of the subscriber lines on the remote terminal with the telephone number. Additional information which may be associated with the subscriber line include, but are not limited to, name and address of the subscriber, emergency responders contact telephone numbers, and related information that would be useful during an emergency. This database may also be used to maintain operational information related to each switch proxy such as, but not limited to, configuration data, current software loads, and time zone. Database  704  must be initially populated correctly and then maintained current, most importantly with respect to subscriber changes. This may be done manually (through e.g., management console  708 ) or in an automated fashion by reference to other databases that are maintained for other purposes such as, but not limited to, the service provider&#39;s operational support system or billing system through interface  710 , or third-party databases such as those maintained by 9-1-1 database providers through interface  712 . Said service provider&#39;s operational support system may be the same system that keeps translation database  212  of local switch  102  current.  
         [0039]     The operation of switch proxy management system  134  will now be described in the context of the flow chart of  FIG. 8  taken in conjunction with the block diagram of  FIG. 7 . Processing starts in circle  800 . In block  802 , controller  702  causes communications unit  706  to interrogate external databases through interfaces  710  and  712  and management console  708  for changes. Processor  702  determines whether the data affects any line served by a switch proxy by comparing the data received to data in database  704  in decision block  804 . If no change affecting any switch proxy is detected, then processing loops back to block  802  and the change is ignored.  
         [0040]     If, in decision block  804 , a change affecting one or more lines served by a switch proxy is detected, then a database lookup is performed on the affected line or lines in block  806 . Changes are recorded in database  704  in block  808 . Finally, all changes are transmitted to the affected switch proxy via communications unit  706 . The changes may be transmitted when discovered or may be transmitted as a batch job during non-peak times.  
         [0041]     While this exemplary embodiment is described in terms of a direct connection between switch proxy management system  134  and one or more switch proxies and external databases through interfaces  710  and  712 , one skilled in the art will appreciate that there are many ways to provide this interconnection. For example, these connections may be over dial-up modems, Ethernet, or proprietary telemetry networks.  
         [0042]     It is to be understood that the above-described embodiments of this invention are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by one skilled in the art without departing from the scope of the invention. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.