Patent Publication Number: US-2002001377-A1

Title: Method for state signaling for a subscriber connection in a communications network with communications systems

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a method for state signaling for a subscriber connection in a communications network with communications systems, wherein a memory which is associated with a first subscriber connection to which a state of a second subscriber connection is to be signaled is used to store a cross-reference to the second subscriber connection, whose state is to be signaled.  
       [0003] 2. Description of the Prior Art  
       [0004] Within a communications system, it is possible to signal state information to dialed destinations, which can be dialed via direct call keys on a communications terminal, on visual display devices which are associated with direct call keys on other communications terminals. For example, a rapidly flashing light-emitting diode can be used to signal an incoming call, a slowly flashing light-emitting diode can be used to signal a state of a parked connection, and a switched-off light-emitting diode can be used to signal a free dialed destination (Hicom 300E V2.0, Description of service features, Section 3.16 and Section 5.3.1, Apr. 23, 1999, Siemens Part Number: P31003-G1036-L100-3-18). A functionality such as this has until now been feasible only within a communications system. To provide the functionality, a memory which is associated with a first subscriber connection to which the state of a second subscriber connection is to be signaled is used to store a cross-reference to the second subscriber connection, whose state is to be signaled. In a corresponding manner, a memory which is associated with the second subscriber connection is used to store a reference back to the first subscriber connection.  
       [0005] An object to which the present invention is directed is to specify a method for state signaling between communications systems for a subscriber connection in a communications network having a number of communications systems.  
       SUMMARY OF THE INVENTION  
       [0006] According to the present invention, at least one memory which is associated with at least one first subscriber connection is used to store a cross-reference to a second subscriber connection. The state of the second subscriber connection can be signaled at the first subscriber connection. For allocation of the first subscriber connection to a first communications system and allocation of the second subscriber connection to a second communications system the at least one first subscriber connection is allocated group information. This group information is stored in a memory which is associated with the second subscriber connection. In the event of a state change of the second subscriber connection, a message relating to the state change is sent with the group information to the first communications system in order to transmit the message onward from there to the first subscriber connection.  
       [0007] An aspect of the method according to the present invention is that, if there are a large number of first subscriber connections to which the state of a second subscriber connection is to be signaled, only a single group information item need be stored in the memory for the second subscriber connection. Even in the case of state signaling between communications systems, this is a major advantage since only one message relating to a state change need be sent per partner communications system within the communications network. This, in turn, contributes to a reduction in the load on the transmission channels. This is extremely advantageous, particularly when transmitting state change messages via signaling channels.  
       [0008] According to one advantageous embodiment of the present invention, in the situation where the first subscriber connection and the second subscriber connection are allocated to the same communications system, a reference back to the first subscriber connection is stored in a memory which is associated with the second subscriber connection. In the event of a state change of the second subscriber connection, a message relating to the state change is then sent directly to the first subscriber connection.  
       [0009] Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Preferred Embodiments and the Drawings. 
     
    
    
     DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 shows a communications network having two communications systems and subscriber connections, whose state is to be signaled on other subscriber connections, or on which the state of other subscriber connections is signaled. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0011]FIG. 1 shows a communications network having two private branch exchange systems PABX 1  and PABX 2 . The private branch exchange system PABX 1  is allocated subscriber connections T 11 , T 21  and T 31 , on each of which the state of at least one other subscriber connection is signaled. The private branch exchange system PABX 2  is allocated subscriber connections T 12  and T 13 , whose state is signaled on another subscriber connection, and is allocated a subscriber connection T 22 , on which the state of another subscriber connection is signaled.  
     [0012] The subscriber connections T 11 , T 21 , T 31  and T 22  are each allocated a subscriber terminal TE having a memory STF in which cross-references are stored to the subscriber connections whose state is to be signaled. In the present case, the memory STF associated with the subscriber connection T 11  contains a cross-reference to the subscriber connection T 12  of the private branch exchange system PABX 2 . Furthermore, the state of the subscriber connection T 12  is to be signaled on the subscriber connection T 21 . For this reason, the memory STF associated with the subscriber connection T 21  likewise has a cross-reference to the subscriber connection T 12 . Since the subscriber connections T 11  and T 21  are allocated to the private branch exchange system PABX 1 , while the subscriber connection T 12  is allocated to the private branch exchange system PABX 2 , the subscriber connections T 11  and T 21  are allocated group information G 1 . This group information GI is also stored in a memory STR associated with the subscriber connection T 12 . Furthermore, a node number N 1  for the private branch exchange system PABX 1  is stored there in addition to the group information G 1 , as a unique identification tag within the communications network. The private branch exchange system PABX 2  is allocated the node number N 2 . Alternatively, it will be possible to use, within the communications system, group information which allows clear conclusions to be drawn relating to the association between those subscriber connections which are provided with corresponding group information and a specific private branch exchange system.  
     [0013] Analogously to the allocation of the group information G 1  to the subscriber connections T 11  and T 21 , the subscriber connections T 21  and T 31  are allocated group information G 2 , since the state of the subscriber connection T 32  associated with the private branch exchange system PABX 2  is to be signaled on both subscriber connections. For this reason, the memories STF which are associated with the subscriber connections T 21  and T 31  via a subscriber terminal TE each contain a cross-reference to the subscriber connection T 32 . Furthermore, the group information G 2 , including the node identification number N 1  of the first private branch exchange system PABX 1 , is stored in the memory STR associated with the subscriber connection T 32 . The association of group information is particularly simple if the subscriber connections to which common group information is allocated are members of a network-wide call transfer group. In this case, this results in additional configuration complexity only for the call transfer group.  
     [0014] Furthermore, the state of the subscriber connection T 12  can be signaled on the subscriber connection T 22  which is associated with the same private branch exchange system PABX 2 . The memory STF associated with the subscriber connection T 22  thus has a cross-reference to the subscriber connection T 12 . In contrast to the situations described above, the memory STR associated with the subscriber connection T 12  is used to store a direct cross-reference back to the subscriber connection T 22  and not to store any group information, since the subscriber connections T 12  and T 22  are allocated to the same communications system PABX 2 .  
     [0015] In the event of a state change of the subscriber connection T 12 , a message m(T 22 , ST) relating to the state change is sent with information relating to the present state ST to the subscriber connection T 22 . Furthermore, a message m(G 1 , NT, ST) indicating the state change ST of the subscriber T 12  is sent with the group information G 1  and the node number N 1  as a sum message to a control unit SE 1  for the private branch exchange system PABX 1 . In this case, the associated message is sent only once for all the group members to the private branch exchange system PABX 1 . The received message relating to the state change of the subscriber connection T 12  is evaluated in the control unit SE 1  of the private branch exchange system PABX 1 , using the group information G 1  contained in the message for this purpose. The received message is passed on in the form of messages m(T 12 , ST) to the subscriber connections T 11  and T 21 , on the basis of the group information G 1  contained in the received message. In a corresponding manner, in the event of a state change of the subscriber connection T 32 , a message m(G 2 , N 1 , ST) is sent to the control unit SE 1 , from where it is passed on to the subscriber connections T 21  and T 31 .  
     [0016] The messages relating to state changes are preferably transmitted via signaling channels to respective partner communications systems in a communications network. As already mentioned, additional information which is contained in the message relating to a state change is stored in a memory which is associated with a subscriber connection to which the state change is to be signaled. The respective state information is preferably signaled visually on a subscriber connection direct call key of a subscriber terminal TE which is associated with the respective subscriber connection. Visual signaling can be produced, for example, by light-emitting diodes flashing at different frequencies or by different color displays.  
     [0017] Although the present invention has been described with reference to specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the spirit and scope of the invention as set forth in the hereafter appended claims.