Abstract:
A communications system having a pre-defined calling group with a plurality of members is disclosed. A plurality of personal communication devices (PCDs) each have a system ID and a group ID, and each member of the group is assigned one of the PCDs. The system ID and the group ID both have a predetermined characteristic, where each system ID has a first variation thereof and each group ID has a second variation. A first group -member having a first PCD contacts a second member having a second PCD by entering into the first PCD the second PCD group ID. The first PCD transmits the first PCD system ID and the second PCD group ID to a communications switch. Based on the first PCD system ID, the communications switch locates a record for the first PCD in a switch database and determines therefrom that the first PCD can contact the second PCD by way of the second PCD group ID. A group database in switchable communication with the communications switch has the system ID and group ID for each group member PCD. The communications switch forwards the contact and the second PCD group ID to the group database for further processing. The group database determines that the second PCD group ID is located therein, locates the second PCD system ID based on the second PCD group ID, and forwards the attempted contact and the second PCD system ID to an appropriate communications switch for further processing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/037,634 filed Jan. 15, 1997 and incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to a communications system having pre-defined restricted user groups. More particularly, the present invention relates to a cellular telephone system wherein at least some group members within such a pre-defined group are restricted to making telephone calls to and receiving telephone calls from other group members only.  
         [0003]     Many organizations have work forces spread out over a relatively wide geographic area. Such work forces and organizations may for example be: drivers for a hauling concern, an ambulance company, a courier company, or the like; work crew members for an electric, cable, or water utility or the like; salespersons for a sales company or the like; service technicians for a copier repair firm, computer repair firm, or the like; repair and maintenance technicians for a climate control service firm, a plumbing or electrical service firm, or the like; roving laborers for a contractor or the like; or security officers for a security firm, private security force, or the like, among others. In most if not all cases, the organizations would prefer to be in close communication with such work force workers.  
         [0004]     Previously, such organizations could only maintain such close contact by building and operating their own private radio communications systems or by contracting with radio communications system service providers. As should be understood, such private systems are quite costly. With the advent of widely available cellular telephone service, however, many organizations have found it advantageous to provide at least some of their work force workers with cellular telephones (“cell phones”). Accordingly, workers, dispatchers, supervisors, and other appropriate personnel can conveniently and easily contact one another, as the case may be. Moreover, such organizations need not expend the costs associated with maintaining or contracting for private radio communications systems.  
         [0005]     As should be evident, with the provided cell phone, each worker can make calls to and receive calls from work-related individuals for work-related purposes. However, each worker may also use the provided cell phone to contact non-work-related individuals for non-work-related purposes. As should be understood, such non-work-related uses may prove to be quite costly and are at any rate considered undesirable. A need exists, then, for a cellular telephone system that prevents at least some workers from using provided cell phones for non-work-related uses.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     In a preferred embodiment of the present invention, the aforementioned need is satisfied by a communications system having a pre-defined calling group with a plurality of members. In particular, in the present invention, a plurality of personal communication devices (PCDs) each have a system ID and a group ID, and each member of the group is assigned one of the PCDs. The system ID and the group ID both have a predetermined characteristic, where each system ID has a first variation with respect to the characteristic and each group ID has a second variation with respect to the characteristic. A first member of the group having a first PCD, then, attempts to contact a second member of the group having a second PCD by entering into the first PCD the group ID of the second PCD.  
         [0007]     A communications switch allows the first PCD to access the communications system thereby. The first PCD transmits information to the communications switch, where the transmitted information includes the system ID of the first PCD and the group ID of the second PCD. A switch database is in communication with the communications switch, and includes a record for the first PCD. The record includes information that the first PCD is assigned to a member of the group. The communications switch locates the record for the first PCD based on the system ID of the first PCD, and determines based on the record for the first PCD that the first PCD is allowed to contact the second PCD by way of the group ID of the second PCD.  
         [0008]     A group database is in switchable communication with the communications switch. The group database has the system ID and the group ID for the PCD of each member of the group. The communications switch forwards the attempted contact and the group ID of the second PCD to the group database for further processing. The group database determines that the group ID of the second PCD is located therein, locates the system ID of the second PCD based on the group ID of the second PCD, and forwards the attempted contact and the system ID of the second PCD to an appropriate communications switch for further processing.  
         [0009]     In a preferred embodiment of the present invention, the calling group has a plurality of members including restricted members and non-restricted members. Each restricted member is restricted to contacting non-restricted members and other restricted members within the group. Each non-restricted member is able to contact restricted members, other non-restricted members, and non-group individuals. The record for the first PCD includes a first designator designating that the first PCD is assigned to a member of the group and a second designator indicating whether the first PCD is assigned to a restricted member or a non-restricted member.  
         [0010]     If the communications switch determines based on the record for the first PCD that the first PCD is assigned to a restricted member, the communications switch allows the attempted contact to proceed if the number of the communications device has the second variation. If the communications switch determines based on the record for the first PCD that the first PCD is assigned to a non-restricted member, the communications switch allows the attempted contact to proceed if the number of the communications device has the first or the second variation. If the communications switch determines based on the record for the first PCD that the first PCD is assigned to a non-restricted member and if the number of the communications device has the first variation, the communications switch forwards the attempted contact and the number of the communications device to an appropriate communications switch for further processing. If the communications switch determines based on the record for the first PCD that the first PCD is assigned to a restricted member or a non-restricted member and if the number of the communications device has the second variation, the communications switch forwards the attempted contact and the number of the communications device to the group database for further processing. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]     The foregoing summary, as well as the following detailed description of a preferred embodiment of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:  
         [0012]      FIG. 1  is a block diagram of a cellular telephone communications system employed in the preferred embodiment of the present invention;  
         [0013]      FIG. 2  is a block diagram of a cellular switch shown in  FIG. 1 ;  
         [0014]      FIG. 3  is a block diagram of a group organized in accordance with the preferred embodiment of the present invention;  
         [0015]      FIG. 4  is a block diagram of the cellular switches shown in  FIGS. 1 and 2  and a group database in accordance with the preferred embodiment of the present invention;  
         [0016]      FIG. 5  is a block diagram of a home location record (HLR) or a visitor location record (VLR) in a switch database associated with one of the cellular switches shown in  FIGS. 1 and 2  in accordance with the preferred embodiment of the present invention; and  
         [0017]      FIG. 6  is a block diagram of the group database shown in  FIG. 4  in accordance with the preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Certain terminology may be used in the following description for convenience only and is not limiting. The words “left”, “right”, “upper”, and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” are further directions toward and away from, respectively, the geometric center of a referenced object. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar importance.  
         [0019]     Referring to  FIG. 1 , there is shown a cellular telephone communications carrier system  11  in accordance with a preferred embodiment of the present invention. In the carrier system  11 , and as should be understood, a plurality of cell phone users each have a cell phone  10  (i.e., a ‘personal communications device (PCD)), and each cell phone  10  is assigned a unique ten-digit cell phone number (three-digit area code+seven-digit number starting with a three-digit exchange) (i.e., a ‘system ID’ with a first variation of a length characteristic). The carrier system  11  is geographically divided into a plurality of regions, where each region has a cell facility or cell  12 , and each cell  12  is assigned to a cellular switch  14 .  
         [0020]     Each cell  12  includes a cellular telephone radio transceiver for establishing two-way cellular communication with any cell phone  10  within the region of such cell  12 . Each cell  12  also includes additional communication facilities for maintaining communications with one of the cellular switches  14 . Such communications with the cellular switch  14  may be by land line, RF, microwave, or any other appropriate communications medium. Typically, a plurality of the cells  12  are assigned to one cellular switch  14 .  
         [0021]     Referring now to  FIG. 2 , each cellular switch  14  typically includes or is in communication with a switch database  16 , and the switch database  16  includes a home location register (HLR)  18  for each of a plurality of cell phones  10 . For any one cell phone  10  in the carrier system  11 , only one cellular switch  14  in the carrier system  11  has a corresponding HLR  18 . Accordingly, the cellular switch  14  with the HLR  18  for the cell phone  10  is the ‘home’ switch for that cell phone  10 , and each cell phone  10  has only one home switch  14 . The home switch  14  of the cell phone  10  is the cellular switch  14  that is contacted to determine which cellular switch  14  the cell phone  10  is registered at.  
         [0022]     When a cell phone user first turns on his or her cell phone  10 , the cell phone  10  registers with one of the cells  12 . Typically, such cell  12  is the cell for the region in which the cell phone  10  is physically located, or the cell for an adjacent region if circumstances so require. As part of such registration, the cell  12  checks with its assigned cellular switch  14  to determine if the switch database  16  of such cellular switch  14  has an HLR  18  for the cell phone  10 . If so, and as discussed above, such cellular switch  14  is the home switch for the cell phone  10 .  
         [0023]     If no HLR  18  for the cell phone  10  is present in the switch database  16 , the cell phone  10  is a ‘visitor’ to such ‘visited’ cellular switch  14 , and a visitor location register (VLR)  20  is created for the cell phone  10  in the switch database  16  of the visited switch  14 . Preferably, the visited switch  14  communicates with the home switch  14  for the visiting cell phone  10 , the HLR  18  for the visiting cell phone  10  is substantially copied from the switch database  16  of the home switch  14 , the VLR  20  for the visiting cell phone  10  is formed in the switch database  16  of the visited switch  14  substantially based on the copied HLR  18 , and the HLR  18  for the visiting cell phone  10  in the switch database  16  of the home switch  14  is updated to reflect that the cell phone  10  is registered at the visited switch  14 .  
         [0024]     Once registered with a cell  12  and a cellular switch  14 , a telephone call (i.e., an attempted contact) is normally made by sending a ten-digit destination phone number from the cell phone  10  (in addition to other information) to the communications switch  14  by way of the cell  12 . This assumes the call is to a U.S. or similar destination. Of course, if the call is to a non-U.S. or similar destination, the destination phone number will likely have more than ten digits. Nevertheless, the term ‘ten-digit call’ and the like will be used below for convenience only.  
         [0025]     Typically, and absent any other restrictions, the ten-digit call is passed from the cellular switch  14  and through a number of other switches (not shown) until a connection is made and the call is completed between the cell phone  10  and the destination telephone corresponding to the destination telephone number, be it another cell phone  10  or a land line phone. For example, if the destination telephone number is a land line number local to the cellular switch  14 , the cellular switch  14  may contact a local telephone company switch to complete the call. Correspondingly, if the destination number is a long-distance land line number, the cellular switch  14  may connect with a long-distance telephone company switch to complete the call. Of course, the cellular switch  14  need not contact any other switches if the destination telephone number is for a cell phone  10  that is home to the cellular switch  14 . Typically, and as seen in  FIG. 2 , each cellular switch  14  (as well as every other non-cellular switch) has a number of input ports  26  and output ports  28  through which connections with other switches are achieved, and trunk lines (not shown) interconnect the communications switches by way of the input ports and output ports  26 ,  28 .  
         [0026]     When a call is made from the outside world to one of the cell phones  10  in the carrier system  11 , the call upon reaching the carrier system  11  is initially switched to the home switch  14  for the cell phone  10 . If the HLR  18  for the cell phone  10  indicates that the cell phone  10  is ‘at home’, the home switch  14  completes the call by way of an appropriate cell  12 . Otherwise, if the HLR  18  for the cell phone  10  indicates that a VLR  20  has been created for the cell phone  10  at a visited switch  14 , the home switch  14  forwards the call to the visited switch  14  for further processing and completion.  
         [0027]     In the preferred embodiment of the present invention, and referring now to  FIG. 3 , at least one group  22  is formed with regard to a particular organization, where each member of the group is designated as a basic member having a basic member cell phone  10   b  or an enhanced member having an enhanced member cell phone  10   e . Additionally, the group  22  may include one or more dispatcher members, where each dispatcher member can access any other member  10   b ,  10   e  within the group by way of a dispatcher land line phone  24 .  
         [0028]     Preferably, each member  10   b ,  10   e ,  24  of the group  22  has a pre-defined shortened number (i.e., a ‘group ID’ with a second variation of a length characteristic) that is used by others in the group  22  to make contact therewith. Preferably, the shortened number is a four-digit number, although one skilled in the art will recognize that other variations of number length may be employed without departing from the spirit and scope of the present invention.  
         [0029]     Moreover, one skilled in the art will recognize that variations of other characteristics besides length may be used to differentiate system IDs from group IDs without departing from the spirit and scope of the present invention. For example, group IDs may be defined as all IDs having a pre-defined beginning or end portion, or as all IDs having a ‘*’ or ‘#’ as a digit, among other things. Nevertheless, the terms ‘four-digit number’, ‘ten-digit number’, and the like will be used below for convenience only.  
         [0030]     Preferably, each basic member  10   b  may only make a call to a pre-defined four-digit number, and may only receive a call from an authorized inbound group member  10   b ,  10   e ,  24 . Also preferably, each enhanced member  10   e  may make and receive four-digit (i.e., group) and ten-digit (i.e., non-group) calls. As should be understood, a basic member having a basic member cell phone  10   b  would typically be a worker who need only be able to communicate with other group members  10   b ,  10   e ,  24 . Correspondingly, an enhanced member having an enhanced member cell phone  10   e  would typically be a worker who needs access to other group members  10   b ,  10   e ,  24 , and also to the outside world, or should otherwise be allowed to have such access. Presumably, the enhanced member  10   e  can be trusted to not misuse his or her cell phone  10 .  
         [0031]     Referring now to  FIG. 4 , there is shown an example that will be useful in describing the preferred embodiment of the present invention. As seen, a first basic member BM 1  is registered to a first cellular switch SW 1 , a second basic member BM 2  is registered to a second cellular switch SW 2 , and a dispatcher member DISP 1  is at a land line phone available by way of a land line switch LL-SW. As also seen, the first cellular switch SW 1  is the home switch for both the first basic member BM 1  and the second basic member BM 2 , as shown by the HLR for BM 1  and the HLR for BM 2  in the switch database DB 1  associated with the first cellular switch SW 1 , and the second cellular switch SW 1  is the visited switch for the second basic member BM 2 , as shown by the VLR for BM 2  in the switch database DB 2  associated with the first cellular switch SW 2 .  
         [0032]     One skilled in the art will appreciate that no cells  12  are shown in or discussed in connection with  FIG. 4  since such cells  12  are not necessary for purposes of describing the preferred embodiment of the present invention. However, such cells  12  are still necessary-in the carrier system  11 . One skilled in the art will also appreciate that although direct connections are shown between the first and second cellular switches SW 1 , SW 2  and between other switches in  FIG. 4 , such connections may in fact be indirect by way of other switches (not shown) without departing from the spirit and scope of the present invention.  
         [0033]     With reference to the example shown in  FIG. 4 , then, a group telephone call from BM 1  to BM 2  is completed as follows. Preliminarily, BM 1  enters the pre-defined four-digit number for BM 2  into his or her cell phone  10 , and then enters ‘send’ or the equivalent to initiate the group call. Thereafter, the cell phone  10  sends to SW 1  the four-digit number for BM 2  and the ten-digit number for BM 1 .  
         [0034]     Based on the ten-digit number for BM 1 , SW 1  locates the HLR  18  for BM 1  in DB 1 . SW 1  then checks such HLR to determine the kind of access that BM 1  is permitted. Preferably, and referring now to  FIG. 5 , each HLR  18  or VLR  20  in any database  16  for any cellular switch  14  includes a primary dialing class (PDC) designator (“first designator”), and a secondary dialing class (SDC) designator (“second designator”). Additionally, the HLR  18  includes an immediate call forwarding (ICF) designator, a visited switch designator, and a home system only designator. Further, the HLR  18  or VLR  20  for any group member  10   b ,  10   e  preferably includes the ten-digit number for the group member  10   b ,  10   e , among other information (not shown). Of course, one skilled in the art will realize that the elements included in the HLR  18  or VLR  20  may vary without departing from the spirit and scope of the present invention so long as the HLR  18  or VLR  20  provides the information necessary for the operability of the present invention, as described below.  
         [0035]     The PDC for the HLR  18  or VLR  20  for any group member  10   b ,  10   e  is set to indicate that the group member  10   b ,  10   e  is indeed a member of a group  22 . The SDC for the HLR  18  or VLR  20  for any group member  10   b ,  10   e  is set to indicate whether a group member is a basic member  10   b  or an enhanced member  10   e . When the SDC is set to indicate that a group member is a basic member  10   b , calls made from the basic member  10   b  are forwarded to a group database  30  (shown in  FIG. 4 ) for further processing. The ICF for the HLR  18  for any basic member  10   b  is set to indicate that calls made to the basic member  10   b  are to be forwarded to the group database  30  for further call processing. The visited switch designator for the HLR  18  for any group member  10   b ,  10   e  indicates whether a VLR  20  exists at a visited cellular switch  14 , and which cellular switch  14 . The home system only designator for the HLR  18  for any group member  10   b ,  10   e  indicates whether the group member  10   b ,  10   e  can visit at cellular switches  14  at other carrier systems  11 . Preferably, the home system only designator for each basic member  10   b  is set to prevent a VLR  20  from being created for the member  10   b  outside the carrier system  11 . Accordingly, a basic member  10   b  is prevented from using the cell phone  10  outside the carrier system  11 . As should be understood, by referring to the HLR  18  or VLR  20  for any group member  10   b ,  10   e  , a cellular switch  14  determines how to handle any call involving such group member  10   b ,  10   e.    
         [0036]     Since the HLR for BM 1  by definition includes an SDC designator that indicates that BM 1  is a basic group member  10   b , the communications switch SW 1  only allows BM 1  to make four-digit (group) calls. That is, if BM 1  were to attempt to make a ten-digit (non-group) call, SW 1  would prevent the call from being further processed and completed.  
         [0037]     Additionally, since the HLR for BM 1  by definition includes the PDC designator set to indicate that BM 1  is a member of a group  10   b  and since the call is a four-digit call, the communications switch SW 1  forwards the BM 1  to BM 2  four-digit (group) call to the group database  30  for further call processing. Preferably, the group database  30  is associated with a group switch  32  such that the group switch  32  facilitates call switching for the group database  30 . Preferably, as part of forwarding the group call from SW 1 , the group database  30  receives the ten-digit number of BM 1  plus the four-digit number of BM 2 .  
         [0038]     Preferably, and referring now to  FIG. 6 , the group database  30  includes a partition  34  for each group  22  in the cellular telephone system, and each partition  34  includes information on each group member  10   b ,  10   e  ,  24  in the respective group  22 . As seen in  FIG. 6 , partitions  34  exist for groups A and B, and BM 1 , BM 2 , and DISP 1  are all in group A. Preferably, and as seen, the group database  30  has the ten-digit number and the four-digit number for each group member  10   b ,  10   e ,  24  in each group  22 . Accordingly, from the received ten-digit number of BM 1 , the group database  30  can determine that BM 1  is in group A, and from the four-digit number of BM 2 , the group database can locate the ten-digit number of BM 2  within group A.  
         [0039]     Since the group database  30  can determine that BM 1  is in group A, the group database preferably only allows BM 1  to make four-digit (group) calls to other group members  10   b ,  10   e ,  24  in group A. That is, if BM 1  were to attempt to make a four-digit (group) call to a group member  10   b ,  10   e ,  24  in group B or any other group, the group database  30  preferably would prevent the call from being further processed and completed.  
         [0040]     Based on the located ten-digit number for BM 2 , the group switch  32  associated with the group database  30  forwards the call to the home switch for BM 2  for further processing in accordance with the ten-digit number for BM 2 . This is necessary since the home switch for BM 2  (SW 1  in this example) maintains the HLR  18  which includes the visited switch designator that indicates whether BM 2  is registered at its home cellular switch  14  or is visiting another cellular switch  14 .  
         [0041]     Preferably, and as seen in  FIG. 6 , each cellular switch  14  is home to a number of cell phone exchanges, and the group database  30  includes an exchange-switch table  36  that lists a home cellular switch  14  for each area code and exchange in the group database  30 . Accordingly, based on the area code and exchange in the ten-digit number for BM 2 , the group database  30  can determine that the home switch for BM 2  is SW 1 . Preferably, when the group call for BM 2  is forwarded to SW 1 , appropriate call information is also forwarded to SW 1 , including the ten-digit number for BM 2 .  
         [0042]     Based on the ten-digit number for BM 2 , switch SW 1  looks at the HLR  18  for BM 2  in DB 1 . Since BM 2  is a basic member  10   b  of the group  22 , the HLR  18  for BM 2  by definition has the ICF designator set to forward all calls to BM 2  to the group database  30  for further processing. Accordingly, the forwarded call from the group database  30  would normally be switched by SW 1  back to the group database  30 . As should be understood, this is undesirable since the call to BM 2  has already been processed by the group database  30 . Accordingly, in the preferred embodiment of the present invention, once the group database  30  processes and forwards a call to a basic member  10 b, the group switch  32  must notify the receiving cellular switch  14  (SW 1  in this example) to suspend immediate call forwarding for this call only.  
         [0043]     Referring again to  FIG. 4  and the four-digit (group) call from BM 1  to BM 2 , since the HLR for BM 2  indicates that BM 2  is visiting SW 2 , switch SW 1  forwards the call to SW 2  for further completion. Once SW 2  receives the call, the call is completed in the normal fashion.  
         [0044]     If BM 2  makes a four-digit (group) call to BM 1 , the call will be handled in the same manner as stated above. However, in such a situation, SW 2  must refer to the VLR for BM 2  to determine the PDC and SDC designators for BM 2 .  
         [0045]     If in the above scenario BM 1  were instead an enhanced member EM 1  (not shown), a four-digit (group) call from EM 1  to BM 2  would cause SW 1  to forward the call to the group database  30  for completion in the same manner as stated above. Likewise, if BM 2  were instead an enhanced member EM 2  (also not shown), a four-digit (group) call from BM 1  to EM 2  would cause SW 1  to forward the call to the group database  30  for completion in the same manner as stated above. However, it should be noted that the ICF designator is not set for an enhanced member  10   e  and that immediate call forwarding therefore need not be suspended at any time. If EM 1  calls a ten-digit (non-group) number or receives a call from a ten-digit (non-group) number, SW 1  would preferably recognize from the HLR  18  for EM 1  that EM 1  is an enhanced member  10   e , would not block the call, and would not forward the call to the group database  30 . In such an instance, SW 1  would preferably complete the call as if EM 1  were not in a group  22 .  
         [0046]     However, if anyone, group or non-group, employs a communications device to call basic member BM 2  by way of the ten-digit number for BM 2 , the call would be routed to SW 1 , the home switch for BM 2 ; SW 1  would determine that the HLR for BM 2  has the ICF designator set; and SW 1  would therefore forward the call to the group database  30  for further processing. Preferably, the group database  30  would complete the call in the manner set forth above only if an appropriate security code were entered or if the caller&#39;s ten-digit number were recognized as a number of a group member. As should be evident, if the group database  30  can recognize a caller&#39;s ten-digit number, a security code need not be required.  
         [0047]     Accordingly, a dispatcher member  24  or the like with the security code and/or a recognized ten-digit number would be able to access any basic member  10   b  of the group  22 , but an inappropriate third party without the security code would not be able to access the any such basic member  10   b  of the group  22 . Preferably, any dispatcher can call a group member either directly by dialing the ten-digit number for the group member and then a security code, or by dialing a telephone access number and the four-digit number for the group member.  
         [0048]     In a situation where BM 1  makes a four-digit call to dispatcher member DISP 1 , the call is forwarded to the group database  30  in the manner explained above. Thereafter, the group database  30  preferably forwards the call to the land line telephone number for DISP 1  by way of the group switch  32  and land line switch LL-SW. As should be understood, since DISP 1  is not a cell phone  10  and is not registered with a cellular switch  14 , no incoming call forwarding suspension is required.  
         [0049]     In the preferred embodiment of the present invention, each cellular switch  14  in a carrier system  11  must be able to recognize that four-digit calls are handled differently than ten-digit calls. Moreover, since multiple carrier systems  11  may have common four-digit numbers for different cell phones  10 , it is preferable that each cell phone  10  be assigned to a ‘home’ carrier system  11 , and that four-digit calls from a cell phone  10  be prevented from being completed through cellular switches  14  not associated with the home carrier system  11  of the cell phone  10 . Also preferably, and as stated above, by setting the home system only designator in the HLR  18  for each basic member  10   b , such basic member  10   b  is prevented from visiting a cellular switch outside the ‘footprint’ of the carrier system  11  and obtaining service. However, one skilled in the art will recognize that allowing a basic member  10   b  to visit a cellular switch outside the ‘footprint’ of the carrier system  11  may be desirable under certain circumstances, and that such an action is therefore within the spirit and scope of the present invention.  
         [0050]     As should be understood, since the code assigned to each group member  10   b ,  10   e ,  24  is preferably four digits, a maximum of ten thousand group members spread across multiple groups  22  are allowed per carrier system  11 . Of course, one skilled in the art will recognize that if the code is five digits, one hundred thousand group members in the carrier system  11  are allowed, that if the code is three digits, one thousand group members in the carrier system  11  are allowed, etc.  
         [0051]     In a preferred embodiment of the present invention, each cellular switch  14  is preferably a Lucent Technologies 5E switch, the group database  30  is an ORYX database designed by Priority Call Management of Wilmington, Mass., and the group switch  32  is an Excel LNX switch from Excel Inc. of Hyannis, Mass. As one skilled in the art will recognize, however, other switches and databases may be employed without departing from the spirit and scope of the present invention.  
         [0052]     From the foregoing description, it can be seen that the present invention comprises a new and useful cellular telephone system with pre-defined restricted groups. It will be appreciated by one skilled in the art that changes can be made to the embodiment described above without departing from the broad inventive concepts thereof. For example, in addition to a cellular telephone system, the present invention may also be deployed in other switched communications systems, including wireless systems such as PCS and SMR and wired systems such as the classic land line telephone system. As should be understood, deploying the present invention in such other systems would require minor variations that would be evident to one skilled in the art. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed but is intended to cover modifications within the spirit and scope of the present invention.