Abstract:
A method for handling incoming calls at a private branch exchange is disclosed. A distinction is made between the address space of the Public Switched Telephone Network and the address space of the private branch exchange handling the incoming calls. The method disclosed accounts for one or more conditions present in the associated network and forwards calls to telephone numbers in the different address spaces based on the conditions present.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to telecommunications in general, and, more particularly, to forwarding telephone calls at a private branch exchange.  
         BACKGROUND OF THE INVENTION  
         [0002]    [0002]FIG. 1 depicts a block diagram of the salient components of telecommunications network  100  in the prior art. Telecommunications network  100  comprises Public Switched Telephone Network  101 , wireline terminal  102 , wireless terminal  103 , private branch exchange  105 , and wireline terminals  106 - 1  through  106 -N.  
           [0003]    Private branch exchange  105  is capable of switching incoming calls from Public Switched Telephone Network  101  via one or more transmission lines to one of wireline terminals  106 - 1  through  106 -N. Private branch exchange  105  is also capable of handling outgoing calls from any of wireline terminals  106 - 1  through  106 -N to Public Switched Telephone Network  101  via one or more transmission lines that connect private branch exchange  105  to Public Switched Telephone Network  101 .  
           [0004]    In addition, private branch exchange  105  is capable of also forwarding each incoming call to a telephone number in Public Switched Telephone Network  101 . The forwarded-to telephone number in Public Switched Telephone Network  101  can correspond to a terminal such as wireless terminal  103 .  
           [0005]    [0005]FIG. 2 depicts the address spaces that are relevant to telecommunications network  100  in the prior art. The term “address space” refers to an addressable region of telephone service. Address space  104  represents the addressable region served by Public Switched Telephone Network  101 . Address space  107  represents the addressable region served by private branch exchange  105 . A distinction is made between address space  104  and address space  107  because the same telephone number has two different meanings in each address space.  
           [0006]    Private branch exchange  105  exists in both address space  104  and address space  107  and acts as a bridge or gateway between the two address spaces. When a calling party places a call to someone served by private branch exchange  105 , the calling party uses a dialing sequence that includes a telephone number belonging to Public Switched Telephone Network  101  and residing in address space  104 . As part of the dialing sequence, the calling party also uses an extension number that allows access to one of the terminals residing within address space  107 .  
           [0007]    [0007]FIG. 3 depicts a flowchart of the tasks that are relevant to processing an incoming call in the prior art. To accomplish tasks  301  through  303 , private branch exchange  105  maintains a table that correlates Public Switched Telephone Network number to private branch exchange extension. Table 1 depicts an illustrative table that correlates Public Switched Telephone Network number to private branch exchange extension.  
                             TABLE 1                           Call Forwarding Database                    Public Switched           Private Branch   Telephone Network           Exchange Extension   Number                       732-555-0102, x11   201-555-1236           732-555-0102, x12   908-555-3381           .   .           .   .           .   .           732-555-0102, x99   212-555-6784                      
 
           [0008]    At task  301 , private branch exchange  105  receives a call from Public Switched Telephone Network  101 , which is originated by wireline terminal  102 .  
           [0009]    At task  302 , private branch exchange  105  forwards the call to a first telephone number. The first telephone number exists in the address space of the private branch exchange, namely address space  107 , and can be associated with one of wireline terminals  106 - 1  through  106 -N. The first telephone number is represented as the private branch exchange extension in Table 1.  
           [0010]    At task  303 , private branch exchange  105  also forwards the call to a second telephone number. The second telephone number exists in the address space of Public Switched Telephone Network  101 , namely address space  104 , and can be associated with a wireless terminal such as wireless terminal  103 .  
           [0011]    Referring to the example in Table 1, the call, placed to 732-555-0102, extension 11 (i.e., shown in the first row), is connected to private branch exchange extension 11 and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention enables an incoming call to a private branch exchange to be forwarded to a private branch exchange extension and to a number in the Public Switched Telephone Network that is selected based on one or more criteria. For example, various embodiments of the present invention select the number in the Public Switched Telephone Network based on the calling-party&#39;s number, the incoming line to the private branch exchange, the dialed number, the calendrical time, the location of a terminal, and/or environmental factors.  
           [0013]    The illustrative embodiment of the present invention comprises: receiving a first call that is associated with a first calling-party telephone number; forwarding the first call to a first telephone number, wherein the first telephone number exists in the address space of a private branch exchange; and forwarding the first call to a second telephone number, wherein the second telephone number exists in the address space of the Public Switched Telephone Network; wherein the first telephone number and the second telephone number are based on the first calling-party telephone number. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 depicts a schematic diagram of telecommunications system  100  in the prior art.  
         [0015]    [0015]FIG. 2 depicts a schematic diagram of address space  104  and address space  107  in the prior art.  
         [0016]    [0016]FIG. 3 depicts a flowchart of tasks relevant to processing an incoming call in the prior art.  
         [0017]    [0017]FIG. 4 depicts a schematic diagram of telecommunications system  400 , in accordance with the illustrative embodiment of the present invention.  
         [0018]    [0018]FIG. 5 depicts a block diagram of private branch exchange  405 , in accordance with the illustrative embodiment of the present invention.  
         [0019]    [0019]FIG. 6 depicts a flowchart of the salient tasks that are relevant to calling-party telephone number, in accordance with the illustrative embodiment of the present invention.  
         [0020]    [0020]FIG. 7 depicts a flowchart of the salient tasks that are relevant to incoming line, in accordance with the illustrative embodiment of the present invention.  
         [0021]    [0021]FIG. 8 depicts a flowchart of the salient tasks that are relevant to dialed number, in accordance with the illustrative embodiment of the present invention.  
         [0022]    [0022]FIG. 9 depicts a flowchart of the salient tasks that are relevant to calendrical time, in accordance with the illustrative embodiment of the present invention.  
         [0023]    [0023]FIG. 10 depicts a flowchart of the salient tasks that are relevant to location of terminal, in accordance with the illustrative embodiment of the present invention.  
         [0024]    [0024]FIG. 11 depicts a flowchart of the salient tasks that are relevant to environmental condition, in accordance with the illustrative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0025]    [0025]FIG. 4 depicts a block diagram of the salient components of telecommunications network  400  in accordance with the illustrative embodiment of the present invention. Telecommunications network  400  comprises Public Switched Telephone Network  401 , wireline terminal  402 , wireless terminals  403 - 1  through  403 -M, wherein M is a positive integer, and the network-facing part of private branch exchange  405 , all situated within the address space of the Public Switched Telephone Network, namely address space  404 , and interconnected as shown. Telecommunications network  400  also comprises the extension-facing part of private branch exchange  405  and wireline terminals  406 - 1  through  406 -N, wherein N is a positive integer, all situated within the address space of the private branch exchange, namely address space  405 , and interconnected as shown. It will be clear to those skilled in the art how to make and use Public Switched Telephone Network  401 , wireline terminal  402 , wireless terminals  403 - 1  through  403 -M, and wireline terminals  406 - 1  through  406 -N. It will be clear to those skilled in the art, after reading this specification, how to make and use private branch exchange  405 .  
         [0026]    Private branch exchange  405  is capable of handling incoming calls from Public Switched Telephone Network  401  via one or more transmission lines for the purpose of forwarding each call to a telephone number corresponding to one of wireline terminals  406 - 1  through  406 -N (i.e., in address space  407 ). In addition, private branch exchange  405  is capable of forwarding each incoming call to a telephone number in address space  404 . The telephone number in address space  404  can correspond to one of wireless terminals  403 - 1  through  403 -M. Private branch exchange  405  is also capable of handling outgoing calls from any of wireline terminals  406 - 1  through  406 -N to Public Switched Telephone Network  401  via one or more transmission lines.  
         [0027]    [0027]FIG. 5 depicts a block diagram of the salient components of private branch exchange  405  in accordance with the illustrative embodiment of the present invention. Private branch exchange  405  comprises: switch matrix  501 , processor  502 , memory  503 , clock  504 , environmental sensor  505 , and wireless terminal location estimator  506 , interconnected as shown.  
         [0028]    Switch matrix  501  is a circuit that is capable of receiving call-related data and traffic from Public Switched Telephone Network  401 , forwarding call-related data to processor  502 , and accepting commands from processor  502 . In addition, switch matrix  501  is capable of handling outgoing calls from wireline terminals  406 - 1  through  406 -N. Switch matrix  501  also is capable of forwarding call traffic to wireline terminals  406 - 1  through  406 -N and also to wireless terminals  403 - 1  through  403 -M in Public Switched Telephone Network  401 . It will be clear to those skilled in the art how to make and use switch matrix  501 .  
         [0029]    Processor  502  is a general-purpose processor that is capable of performing the tasks described below and with respect to FIGS. 6 through 11. It will be clear to those skilled in the art, after reading this specification, how to make and use processor  502 .  
         [0030]    Memory  503  is capable of storing programs and data used by processor  502 . It-will be clear to those skilled in the art how to make and use memory  503 .  
         [0031]    Clock  504  is capable of tracking calendrical time at one or more levels of granularity, such as months, days of the week, days of the month, time of day, etc. Clock  504  can generate the time internally or it can obtain the time from another source or both. Processor  502  uses the calendrical time tracked by clock  504 . It will be clear to those skilled in the art how to make and use clock  504 .  
         [0032]    Environmental sensor  505  is capable of tracking one or more environmental conditions. Environmental conditions can include rain, wind, sunshine, air quality, presence of seismic activity, etc. Environmental sensor  505  can directly sense the environment or it can store environmental data obtained from another source or both. It will be clear to those skilled in the art how to make and use environmental sensor  505 .  
         [0033]    Wireless terminal location estimator  506  is capable of tracking the location of one or more of wireless terminals  403 - 1  through  403 -M. Wireless terminal location estimator  506  can directly determine the location of the wireless terminal or it can store location data obtained from another source or both. It will be clear to those skilled in the art-how to make and use wireless terminal location estimator  506 .  
         [0034]    [0034]FIG. 6 depicts a flowchart of the salient tasks that are relevant to calling-party number and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 6 can be performed simultaneously or in a different order than that depicted.  
         [0035]    To accomplish tasks  601  through  606 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to calling-party telephone number. Each unique combination of calling-party telephone number, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 2 depicts an illustrative version of this table.  
                                           TABLE 2                           Call Forwarding Database Based on Calling-Party Telephone Number            Virtual Station                    Physical                   Private Branch       Public Switched       Calling-Party   Exchange   Alert   Telephone Network       Telephone Number   Extension   Pattern   Number               609-555-0102   1   1   201-555-1236       516-555-9981   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       732-555-3456   N   1   212-555-6784                  
 
         [0036]    The calling-party telephone number identifies the person (or terminal) originating a telephone call. It will be clear to those skilled in the art how to use calling-party telephone number.  
         [0037]    At task  601 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first calling-party telephone number. For example, wireline terminal  402  can originate the call as the first calling party.  
         [0038]    At task  602 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first calling-party telephone number. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 2.  
         [0039]    Private branch exchange  405  can also forward to the first telephone number alerting information that is also based on the first calling-party telephone number. The particular alert pattern that is forwarded can be used to provide distinctive ringing. The distinctive ringing can be used, for example, by multiple users of a single wireline terminal (e.g., wireline terminal  406 - 1 , etc.) to help determine the recipient of the call prior to answering. It will be clear to those skilled in the art how to forward alert information.  
         [0040]    At task  603 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first calling-party telephone number. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0041]    Referring to the example in Table 2, the first call, received from calling-party telephone number 609-555-0102, is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0042]    At task  604 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second calling-party telephone number. For example, wireless terminal  403 - 1  can originate the call as the second calling party.  
         [0043]    At task  605 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second calling-party telephone number.  
         [0044]    Private branch exchange  405  can also forward to the first telephone number alerting information that is also based on the second calling-party telephone number. The particular alert pattern that is forwarded can be used to provide a distinctive ring. As depicted in Table 2, the alert pattern associated with the second calling-party telephone number (i.e., alert pattern “2”) can be different that associated with the first calling-party telephone number (i.e., alert pattern “1”).  
         [0045]    At task  606 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second calling-party telephone number. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0046]    Referring to the example in Table 2, the second call, received from calling-party telephone number 516-555-9981, is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0047]    [0047]FIG. 7 depicts a flowchart of the salient tasks that are relevant to incoming line and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 7 can be performed simultaneously or in a different order than that depicted.  
         [0048]    To accomplish tasks  701  through  706 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to incoming line. Each unique combination of incoming line, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 3 depicts an illustrative version of this table.  
                                           TABLE 3                           Call Forwarding Database Based on Incoming Line            Virtual Station                    Physical                   Private Branch       Public Switched           Exchange   Alert   Telephone Network       Incoming Line   Extension   Pattern   Number               732-555-0001   1   1   201-555-1236       732-555-0002   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       732-555-9999   N   1   212-555-6784                  
 
         [0049]    The incoming line is a transmission path terminated at private branch exchange  405  that is capable of carrying a call from Public Switched Telephone Network  401 . There are multiple ways to designate an incoming line; in the illustrative embodiment, incoming line is designated using telephone number. It will be clear to those skilled in the art how to use incoming line.  
         [0050]    At task  701 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first incoming line.  
         [0051]    At task  702 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first incoming line. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 3.  
         [0052]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the first incoming line.  
         [0053]    At task  703 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first incoming line. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0054]    Referring to the example in Table 3, the first call, received on incoming line 732-555-0001, is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0055]    At task  704 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second incoming line.  
         [0056]    At task  705 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second incoming line.  
         [0057]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the second incoming line.  
         [0058]    At task  706 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second incoming line. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0059]    Referring to the example in Table 3, the second call, received on incoming line 732-555-0002, is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0060]    [0060]FIG. 8 depicts a flowchart of the salient tasks that are relevant to dialed number and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 8 can be performed simultaneously or in a different order than that depicted.  
         [0061]    To accomplish tasks  801  through  806 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to dialed number. Each unique combination of dialed number, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 4 depicts an illustrative version of this table.  
                                           TABLE 4                           Call Forwarding Database Based on Dialed Number            Virtual Station                    Physical                   Private Branch       Public Switched           Exchange   Alert   Telephone Network       Dialed Number   Extension   Pattern   Number               732-555-8435   1   1   201-555-1236       732-555-9858   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       732-555-0475   N   1   212-555-6784                  
 
         [0062]    The dialed number is a telephone number assigned to represent a specific pair of physical private branch exchange extension and Public Switched Telephone Network number. Dialed number is the telephone number that the calling party specifies while dialing (e.g., 732-555-8435, etc.), instead of the actual physical number associated with a terminal being called (e.g., extension 1 at private branch exchange  405 , etc.). It will be clear to those skilled in the art how to use dialed number.  
         [0063]    At task  801 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first dialed number.  
         [0064]    At task  802 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first dialed number. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 4.  
         [0065]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the first dialed number.  
         [0066]    At task  803 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first dialed number. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0067]    Referring to the example in Table 4, the first call, received for dialed number 732-555-8435, is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0068]    At task  804 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second dialed number.  
         [0069]    At task  805 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second dialed number.  
         [0070]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the second dialed number.  
         [0071]    At task  806 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second dialed number. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0072]    Referring to the example in Table 4, the second call, received for dialed number 732-555-9858, is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0073]    [0073]FIG. 9 depicts a flowchart of the salient tasks that are relevant to calendrical time and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 9 can be performed simultaneously or in a different order than that depicted.  
         [0074]    To accomplish tasks  901  through  906 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to calendrical time. Each unique combination of calendrical time, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 5 depicts an illustrative version of this table.  
                                           TABLE 5                           Call Forwarding Database Based on Calendrical Time            Virtual Station                    Physical                   Private Branch        Public Switched           Exchange   Alert   Telephone Network       Calendrical Time    Extension   Pattern    Number               Morning   1   1   201-555-1236       Afternoon   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       Saturday   N   1   212-555-6784                  
 
         [0075]    Calendrical time can be used to track repeating occurrences of time, such as a specific part of each month (e.g., the first week of the month, etc.), of each week (e.g., Tuesdays, etc.), of each day (e.g., mornings, etc.), and so on. For example, private branch exchange  405  might have to handle calls one way if the calls are received in the morning, versus another way if the calls are received during another time of the day. It will be clear to those skilled in the art how to use calendrical time.  
         [0076]    At task  901 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first calendrical time.  
         [0077]    At task  902 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first calendrical time. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 5.  
         [0078]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the first calendrical time.  
         [0079]    At task  903 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first calendrical time. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0080]    Referring to the example in Table 5, the first call, received at the calendrical time of morning, is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0081]    At task  904 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second calendrical time.  
         [0082]    At task  905 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second calendrical time.  
         [0083]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the second calendrical time.  
         [0084]    At task  906 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second calendrical time. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0085]    Referring to the example in Table 5, the second call, received at the calendrical time of afternoon, is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0086]    [0086]FIG. 10 depicts a flowchart of the salient tasks that are relevant to location of terminal and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 10 can be performed simultaneously or in a different order than that depicted.  
         [0087]    To accomplish tasks  1001  through  1006 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to location of terminal. Each unique combination of location of terminal, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 6 depicts an illustrative version of this table.  
                                           TABLE 6                           Call Forwarding Database Based on Location of Terminal            Virtual Station                    Physical                   Private Branch       Public Switched       Location of   Exchange   Alert   Telephone Network       Terminal   Extension   Pattern   Number               Chicago   1   1   201-555-1236       New York   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       Munich   N   1   212-555-6784                  
 
         [0088]    The location of terminal refers to the position of a selected terminal, as tracked by private branch exchange  405 . For illustrative purposes, this specification uses the location of wireless terminal  403 - 1  as the location of terminal. It will be clear to those skilled in the art how to use location of terminal and how to select a particular terminal to evaluate the location of.  
         [0089]    At task  1001 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first location of terminal.  
         [0090]    At task  1002 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first location of terminal. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 6.  
         [0091]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the first location of terminal.  
         [0092]    At task  1003 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first location of terminal. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0093]    Referring to the example in Table 6, because the location of wireless terminal  403 - 1  is Chicago, the first call is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0094]    At task  1004 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second location of terminal.  
         [0095]    At task  1005 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second location of terminal.  
         [0096]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the second location of terminal.  
         [0097]    At task  1006 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second location of terminal. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0098]    Referring to the example in Table 6, because the location of wireless terminal  403 - 1  is New York, the second call is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0099]    [0099]FIG. 11 depicts a flowchart of the salient tasks that are relevant to environmental condition and are performed by the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in FIG. 11 can be performed simultaneously or in a different order than that depicted.  
         [0100]    To accomplish tasks  1101  through  1106 , private branch exchange  405  maintains a table that correlates physical private branch exchange extension, alert pattern, and Public Switched Telephone Network number to environmental condition. Each unique combination of environmental condition, physical private branch extension, and alert pattern characterize a specific called entity, referred to as a “virtual station.” Table 7 depicts an illustrative version of this table.  
                                           TABLE 7                           Call Forwarding Database Based on Environmental Condition            Virtual Station                    Physical                   Private Branch       Public Switched       Environmental   Exchange   Alert   Telephone Network       Condition   Extension   Pattern   Number               High Humidity   1   1   201-555-1236       Low Humidity   1   2   908-555-3381       .   .   .   .       .   .   .   .       .   .   .   .       High Ozone Level   N   1   212-555-6784                  
 
         [0101]    The environmental condition refers to a particular state (e.g., high, low, etc.) of a monitored attribute (e.g., humidity, etc.) at a particular location. The location can be, for example, the location of private branch exchange  405 . It will be clear to those skilled in the art how to select and use environmental condition, how to quantify the state, and how to select a particular location to evaluate the environmental condition of.  
         [0102]    At task  1101 , private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a first call that is associated with a first environmental condition.  
         [0103]    At task  1102 , private branch exchange  405  forwards the first call to a first telephone number, wherein private branch exchange  405  selects the first telephone number based on the first environmental condition. The first telephone number exists in the address space of the private branch exchange, namely address space  407 , and can be associated with one of wireline terminals  406 - 1  through  406 -N. The first telephone number is represented as physical private branch exchange extension in Table 7.  
         [0104]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the first environmental condition.  
         [0105]    At task  1103 , private branch exchange  405  also forwards the first call to a second telephone number, wherein private branch exchange  405  selects the second telephone number based on the first environmental condition. The second telephone number exists in the address space of Public Switched Telephone Network  401 , namely address space  404 , and can be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0106]    Referring to the example in Table 7, because the environmental condition is high humidity, the first call is forwarded to physical private branch exchange extension 1 with alert pattern  1  applied and is also forwarded to Public Switched Telephone Number 201-555-1236.  
         [0107]    At task  1104 , some time later, private branch exchange  405  receives from Public Switched Telephone Network  401 , in well-known fashion, a second call that is associated with a second environmental condition.  
         [0108]    At task  1105 , private branch exchange  405  forwards the second call to the first telephone number, wherein private branch exchange  405  selects the first telephone number based on the second environmental condition.  
         [0109]    Private branch exchange  405  can also forward to the first telephone number alerting information, described earlier, that is also based on the second environmental condition.  
         [0110]    At task  1106 , private branch exchange  405  also forwards the second call to a third telephone number, wherein private branch exchange  405  selects the third telephone number based on the second environmental condition. The third telephone number exists in the address space of Public Switched Telephone Network  401  and can, for example, be associated with one of wireless terminals  403 - 1  through  403 -M.  
         [0111]    Referring to the example in Table 7, because the environmental condition is low humidity, the second call is forwarded to physical private branch exchange extension 1 with alert pattern  2  applied and is also forwarded to Public Switched Telephone Number 908-555-3381.  
         [0112]    It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those 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.