Abstract:
The invention relates to a method of existing a collect information phase at an IN service switching pont in such a way that call set-up control is transferred from the IN service switching point (SSP) to the control point (SCP), even though the maximum of information requested as additional information by the IN service control point has not been received. In the method, a new condition (EE) is determined for the collecting phase (PIC 2 ) and after the condition is fulfilled, the collecting phase is exited in such a way that the service control point (SCP) can make a decision how the call will be continued. The condition (EE) is either the maximum collecting time (collectTimer), which determines for how long the collecting of information is allowed to take at the most, or the minimum number (minNumberOfDigits), which determines how may digits as least have to be collected. The invention further related to an intelligent network, an IN service control point and an IN service switching point, to which the method can be applied.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to set-up of a call using an intelligent network service and in particular to a phase in the call set-up in which information is collected from a subscriber. 
     By means of an intelligent network (IN) a large number of different services can be offered to the subscriber to a telecommunication network, for instance a fixed telephone network or a mobile telephone network, These services comprise, for instance, a virtual private network (VPN), which enables the use of private numbers, and a personal number, in which the IN re-routes calls made to the personal number in a manner controlled by the subscriber. One example of the IN of this kind is described in the ITU-T (the International Telecommunications Union) recommendations of Q.1200 series. The invention and its background will be described in the following by using the CoreINAP terminology of the standard ETS 300 374-1, but the invention can also be applied to intelligent networks implemented by other IN standards, 
     In the intelligent network, connection arrangements and service control are separated from one another, so that the IN services will be made independent of the connection arrangements. Equipment or a network element performing tasks assigned by the IN service control function or functions SCF (Service Control Function) is called a service control point SCP (Service Control Point). Within the scope of the present application the SCF and SCP are equal and hereinafter the term SCP will be used. The SCP gives call set-up instructions to the switching center or the switching center may query the SCP about call set-up instructions. Switching centers that are in charge of the intelligent network switching are called service switching points SSP (Service Switching Point). They comprise at least a service switching function SSF (Service Switching Function) and a call control function CCF (Call Control Function). The call control function CCF is not an IN-related function, but it is a standard switching center function comprising high-level call processing functions, such as establishment and release of transmission connections. The service switching function SSF is an interface between the call control function CCF and the service control point SCP. Within the scope of the present application, the service switching point SSP is equal in value to the functional entity formed by the CCF and SSF, and hereinafter the term SSP will be used. 
     In the conventional call set-up, effected without the assistance of the intelligent network, the switching center make independently all the deductions about call routing, In the intelligent network, deductions about routing are also made by the SCP. A basic call state model BCSM defined in connection with the intelligent network describes different phases of the call set-up, In the intelligent network specifications, call processing procedures to be effected at a switching point are roughly grouped into phases which are called ‘points in call’ PIC. When the phase PIC terminates, a detection point DP is in general encountered. Call set-up or release can be temporarily stopped at these detection points and further call processing instructions can be requested from the service control point SCP. Call control can be transferred to the service control point at these detection points. When a transition is made from the detection point DP to the phase PIC, the call control transfers to a switching point. In addition to PICs and detection points DPs, the basic call state model BCSM comprises transitions and events. The transitions indicate proceeding of the basic call set-up from one PIC to another. The events cause transitions into and from the PIC. Messages between the service switching point and the control point are called operations. For instance, the SSP may involve a determination to continue, in response to a CollectInformation operation, the call set-up from PIC 2  where information from the subscriber is collected. In connection with activation of an intelligent network service the SCP sends the SSP a RequestReportBCSMEvent operation, by means of which the SCP designates the detection points where it wishes to stop the call processing at a later stage of the call set-up and to assume the call control at that point for giving instructions to the switching point. 
     Collect Information PIC 2  is one phase in the call set-up. It is normally encountered in the call set-up, when a phase is achieved where it has to be made sure that information has been obtained sufficiently. PIC 2  is also encountered when the SCP requests to collect additional information with the Collectlnformation operation. In this case, prior to the Collectlnformation operation the control point SCP has transmitted the number of digits to be collected in the RequestReportBCSMEvent operation. This number indicates the maximum number of digits to be collected, which term will be used for it hereinafter. One digit refers to any one of figures 0 to 9 or some other character that can be used for call routing. 
     In PIC 2  information is collected from the calling party from the sequence of dialled numbers. Such information includes e.g. service codes, prefixes, dialled address digits, et cetera. The switching point examines the received information. Phase exit events include: reception of complete information, collect time out, collect info failure, invalid information and calling party terminates the call. The reception of complete information is detected when the requisite number of dialled digits is collected or a string of digits ends in an end mark. The requisite number is either the maximum number transmitted in the Collectinformation operation by the SCP or a parameter determined for the SSP. The detection of this event results in encountering Information Collected DP 2 . Call processing is interrupted, the collected information is conveyed to the service control point, call control is transferred to the control point and the switching point remains waiting for instructions on how the call set-up will be continued, The Collect Time Out event is detected when a normal inter-digit timer expires and the maximum of additional information requested by the SCP has not been received in the course of the collecting time. The detection of this event causes a direct transition to PIC 6  (Exception), in which the call is released. The Collect Info Failure event is detected when there is no digit receiver available at the service switching point, i.e. the resources of the switching point are engaged. The detection of this event will also lead to a direct transition to PIC 6 , in which the call is released. The Invalid Information event is detected when an error is found in the information received from the calling party. The detection of this event will also lead to a direct transition to PIC 6 , in which the call is released. The detection of the Calling Party Terminates the Call event results in encountering the detection point DP 1 O (O-Abandon) and the call will be released. 
     The above-described arrangement of Collect Information phase PIC 2  has a drawback that the Collect Time Out event automatically releases the call without the service control point being able to interfere. The DP 2  is designated as a detection point prior to a command, and the only way by which the SCP can interfere with the encounter is the maximum number of additional information digits. If the SCP service is based on the length of the dialled number and if signalling between the local switching center and the switching point that relays the numbers does not support the All Information Received mark, the IN services utilizing the number of dialled digits operate only within the areas of specific switching centers. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The object of the invention is to provide a method and equipment implementing the method in such a way that the above drawbacks can be solved. The objects of the invention are achieved with method of exiting a collect information phase performed at i service switching point of an intelligent network, the method being characterized in that a maximum collecting time, which defines how long information collecting is allowed to take at most, is set as a condition in the collect phase, time consumed in the collect phase is compared with the maximum collecting time, the collect phase is exited in response to the expiring maximum collecting time and the call connection set-up control is transferred from the IN service switching point to the control point in response to the exit. 
     The invention further relates to a method of exiting the collect information phase performed at the IN service switching point, the method being characterized in that a minimum number, which defines how many digits at least have to be collected, is set as a condition in the collect phase, the number of the collected digits is compared with the minimum number when exiting the collect phase and the call connection set-up control is transferred from the IN service switching point to the control point, if there is at least the minimum number of collected digits. 
     The invention also relates to an intelligent network, to which the method of the invention can be applied. The intelligent network of the invention is characterized in that the service control point is arranged to determine the maximum collecting time it can wait for the information and to transmit the maximum collecting time to the service switching point, and the service switching point is arranged to receive the maximum collecting time and, in response to the expiring maximum collecting time, to send the collected information to the service control point and to transfer the call control to the service control point. 
     The invention further relates to an IN service switching point which can be utilized in the method and intelligent network in accordance with the invention. The IN service switching point of the invention is characterized by comprising reception means for receiving the condition of the information collecting operation from the service control point, the condition being the maximum duration for monitoring on information collecting time of a timer, setting means for setting the timer value to conform to the maximum time received from the control point, and transfer means responsive to the timer for transferring call control to the service control point. 
     Additionally, the invention further relates to an IN service switching point which can be utilized in the method and intelligent network in accordance with the invention. The IN service switching point of the invention is characterized by comprising reception means for receiving the condition of the information collecting operation from the service control point, the condition being the minimum length of the information to be collected, comparison means (CCF) for comparing the length of the collected information with the minimum length, and transfer means (SSF-FSM) responsive to the comparison means for transferring call control of the service control point. 
     Also, the invention further relates to an IN service control point which can be utilized in the method and intelligent network in accordance with the invention. The IN service control point of the invention is characterized by comprising determination means for determining the collecting time, which indicates for how long information will be collected at the service switching point, and transmission means are arranged to transmit the collecting time to the service switching point. 
     The invention is based on the idea that call control is returned to the service control point SCP even when in PIC 2  the received information is not the maximum requested as additional information by the SCP. This enables the service control point to decide how the call will be continued. According to the prior art, the call is always released in these cases. Thus, an advantage of the invention is that the service control point can always make a decision on how the call will be continued on the basis of the received information irrespective of whether the requested amount of information is received or not. One more advantage of the invention is that its implementation only requires relatively insignificant changes at the IN service control point SCP and service switching point SSP. 
     In one preferred embodiment of the invention, the service control point SCP is able to influence how long the information will be waited for. This enables e.g. the IN services where a different amount of information in a specific time leads to a different facility, irrespective of whether, for instance, the relaying switching center supports the All Information Received mark or not. One more advantage of this embodiment is that it makes it possible to standardize the waiting time of collect information. The time of expiry of an inter-digit timer depends on the inter-exchange signalling and different signallings employ different times of expiry. Since the switching center receives calls through various incoming circuits, using different signallings, the waiting time of collect information varies in prior art solutions without the SCP having any influence on the collecting time. 
     In one preferred embodiment of the invention the service control point determines the minimum of the information to be collected. The minimum indicates how many digits the control point needs at least for continuation of the call set-up. When information collecting terminates, for instance, because the All Information Received mark was received or the inter-digit timer expired, call processing at the service switching point SSP is interrupted and it is checked whether information was received, at least the minimum sent by the control point. Call control is transferred to the control point and the switching point will remain waiting for instructions from the service control point only if at least the minimum amount of information is received. If the received information is less than the minimum amount, a transition to PIC 6  is performed and the call will be released. This embodiment has an advantage that unnecessary signalling in the network is avoided in situations that result in releasing the call due to insufficient information. 
     The preferred embodiments of the method, intelligent network, IN service switching point and control point in accordance with the invention appear from the accompanying dependent claims  2 ,  4 ,  6 ,  8  and  11 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following the invention will be described in greater detail in connection with preferred embodiments with reference to the accompanying drawings, in which 
     FIG. 1 illustrates an intelligent network (IN), 
     FIG. 2 illustrates signalling in a first preferred embodiment of the invention, and 
     FIG. 3 is a flow chart of the first preferred embodiment of the invention, 
     FIG. 4 is a flow chart of a third preferred embodiment of the invention, 
     FIG. 5 illustrates an IN service switching point, and 
     FIG. 6 illustrates an IN service control point. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an intelligent network IN and a few examples of telecommunication systems related thereto. FIG. 1 illustrates elements and functions that are essential from the viewpoint of IN services. Network elements which comprise a service switching function SSF and a call control function CCF are called service switching points SSPs. The call control function CCF is not an IN-related function, but it is a standard switching center function comprising the high-level call processing functions, such as establishment and release of transmission connections. The service switching function SSF is an interface between the call control function CCF and the service control point SCP. The SSF interprets the requests sent by the SCF and relays them to the CCP which starts the necessary call control functions. Correspondingly, the call control function CCF employs the SSF to request instructions from the SCF. The SSF is tightly coupled to the CCF whose interface it is. So each SSF together with the CCF is located at the same switching center. A service switching point of the invention is described in greater detail in connection with FIG.  5 . 
     Network elements which comprise the service control function SCF are called a service control point SCP. The service control function is a centralized authority in the intelligent network comprising, for instance, an execution environment for service logic programs. In connection with an IN service, a service logic program is started at the service control point SCP and the operation of this program determines the instructions which the SCP transmits to the SSP in each call phase. Each program may have a plurality of instances to be executed. The service control point of the invention is described in greater detail in FIG.  6 . The service control point SCP of FIG. 1 illustrates the service control point at its simplest, since it only comprises the service control function SCF and the necessary connections. 
     A service data function SDF is a database employed by the SCF. The service logic programs may query and update SDF information. For instance, subscriber-specific or service-number-specific information can be stored in the SDF. The SDF can be either a database management system at the service control point SCP or, as illustrated in FIG. 1, a separate database point SDP (Service Data Point) which supports the SCF-SDF interface and comprises a database DB. 
     A specialized resource function SRF, of the intelligent network is an interface for such network mechanisms that relates to interaction with the subscriber. The SRF can be associated with intelligent peripherals IPs which comprise more developed speech processing functions than the switching center or it can be located at the service switching point SSP. 
     In addition, FIG. 1 illustrates an exchange EX, not pertaining to the intelligent network, which, in addition to the CCF, comprises a call control agent function CCAF providing the users with access to the network. Because the EX comprises the CCAF, it may be e.g. a local exchange of a axed telephone network or a mobile telephone exchange controlling a base station sub-system BSS of a mobile network PLMN. The CCAF may also be located at the service switching point. 
     In FIG. 1, the network elements are interconnected by means of a signalling network SS 7 . Other networks, such as ISDN, can also be used. 
     FIG. 2 illustrates a CollectInformation operation, which requests information to be collected, in a first preferred embodiment of the invention. At point  2 - 1  the service control point SCP transmits the Collectinformation operation to the service switching point SSP. Unlike the prior art, the operation comprises parameters. In the first preferred embodiment these parameters are: collectTimer, which determines the maximum time for information collecting; and minNumberOfDigits, which indicates the minimum number of digits to be collected. When the SSP receives the operation, it assumes the call set-up control and performs a transition to PIC 2  Collectinginformation. In addition to the prior art exit events (not shown in the figure), the SSP provides for exiting PIC 2  an exit event EE in which the maximum collecting time defined by the control point has expired and at least the minimum number of digits has been collected. The detection of the exit event PE causes the service switching point to exit PIC 2  and to encounter the detection point DP 2 . The encounter with the detection point causes interruption in call processing at the service switching point SSP. At point  2 - 2  the service switching point SSP sends a prior art response operation EventReportBCSM to the service control point SCP, whereafter the call control transfers to the service control point and the SSP remains waiting for instructions from the service control point SCP. The parameter calledPartyNumber of the response operation includes the digits that were received within the maximum collecting time. 
     In a second preferred embodiment of the invention the exit event EE is detected when at least the minimum number of digits has been collected and either the inter-digit timer expires or the maximum collecting time is up. Otherwise the second preferred embodiment does not differ from the first preferred embodiment. 
     In a third preferred embodiment of the invention, only a maximum collecting time, collectTimer, is the parameter of the operation transmitted at point  2 - 1  In this case, the exit event EE is detected when the maximum collecting time is expired. Irrespective of the number of collected digits, a transition from PIC 2  to the detection point DP 2  is performed. Otherwise the third preferred embodiment does not differ from the first one. 
     In the third preferred embodiment of the invention, only a minimum number minNumberOfDigits is the parameter of the operation transmitted at point  2 - 1 . In this case, the exit event EE is detected when at least the minimum number of digits has been collected and either the inter-digit timer expires or the string of digits ends in an end mark. Otherwise the third preferred embodiment does not differ from the first preferred embodiment. 
     The parameters transmitted in the operation of point  2 - 1 , or one of them, could be relayed to the service switching point also in the initialization operation RequestReportBCSMevent by adding new parameters thereto. By sending the parameters in the Collectlnformation operation the advantage is achieved that they are not sent until they are actually needed. 
     The flow chart of FIG. 3 illustrates the IN operation in accordance with the invention at the service switching point SSP in the first preferred embodiment. It is assumed in the figure that the calling party does not disconnect the call, does not give invalid information, and that there are available resources at the service switching point. At point  301  the Collectinformation operation is received, whereafter, at point  302 , conditions of the exit event of the invention are set for the maximum collecting time T COL , which will have the parameter value of the maximum collecting time collectTimer described in connection with FIG. 2, and for the minimum number to be collected min#, which will have the parameter value of the minimum number of digits to be collected minNumberOfDigits described in connection with FIG.  2 . Thereafter, the call control is transferred to the function CCF and at point  303  collection of information is started in a normal manner. Next, checking of points  304 ,  305 ,  306  and  307  is repeated until one of the conditions of the points is fulfilled. At point  304 , it is checked whether the time T SPE  spent for collecting information is at least the maximum collecting time T COL . If T SPE  is less than T COL , a transition is performed to point  305 , where it is checked, whether the number is the same or larger than the required number max. The required number is either the maximum number of requisite digits sent in the RequestReportBCSMEvent operation by the control point or, if that is not received, the required number of digits set by the service switching point itself. If the number is less than max#, a transition is performed to point  306 , where it is checked, whether the received information includes an acknowledgement SC (Send Completed), which indicates that the calling party has already given complete information. If the received information does not include the acknowledgement, a transition is performed to point  307 , where it is checked, whether the time T SPE  spent for collecting information is at least the time T NET  which triggers the inter-digit timer for transmission network signalling. If not, a return to point  304  is performed. 
     If it is detected at point  304  that the maximum collecting time, i.e. T SPE ≧T COL , was spent for collecting information, a transition is performed to point  308 , where it is checked, whether information was collected at least for the minimum amount of digits needed by the service control point, i.e. nr≧min#. If a sufficient number of digits was collected, a transition is performed to point  309 , where a detection point DP 2  Information Collected is encountered. In accordance with the prior ar, from point  309  the process continues by sending the collected digits to the control point and by transferring the call control to the control point. Point  309  is also entered from point  305 , if the number of collected digits is at least the number required, i.e. nr≧max#, and from point  306  if the SC is received. 
     If the number of digits collected at point  308  is insufficient, i.e. nr&lt;min#, the process will be continued from point  310 , At point  310 , a transition is made to PIC 6  of the BCSM, where the call will be released. Point  310  can also be entered from point  307  if the time T SPE  spent for collecting information is at least the time T NET  which triggers the inter-digit timer for transmission network signalling. 
     In the second preferred embodiment the process proceeds as described above, with the exception that from point  307  a transition is performed to point  308 , and not to point  310 , if the time T SPE  spent for collecting information is at least the time T NET  which triggers the inter-digit timer for transmission network signalling. This enables the encounter with the detection point DP 2  when the inter-digit timer expires, if digits have been collected sufficiently when the time which triggers the inter-digit timer is shorter than the maximum collecting time. 
     In the third preferred embodiment the process proceeds as in the first preferred embodiment with the exception that at point  302  only a value of the maximum collecting time T COL  is given, and no checking on the number of collected digits is performed at point  308 . 
     The flow chart of FIG. 4 illustrates the IN operation in accordance with the invention at the service switching point SSP in a fourth preferred embodiment. It is assumed in the figure that the calling party does not disconnect the call, does not give invalid information and that there are available resources at the service switching point. At point  401  the Collectinformation operation is received, whereafter at point  402  a condition of the exit event of the invention is set for the minimum number min# to be collected, which will have the parameter value of the minimum number of digits to be collected minNumberOfDigits described in connection with FIG.  2 . Thereafter the call control is transferred to the function CCF and at point  403  collection of information is started in a normal manner. Next, checking of points  405 ,  406  and  407  is repeated, until any one of the conditions of the points is fulfilled. At point  405  it is checked whether the number of collected digits nr is the same or larger than the required number max#. The required number is either the maximum number of requisite digits sent in the RequestReportBCSMEvent operation by the control point or, if that is not received, the required number of digits set by the service switching point itself. If the number is less than max#, a transition is performed to point  406 , where it is checked, whether the received information includes an acknowledgement SC (Send Completed), which indicates that the calling party has already given complete information. If the received information does not include the acknowledgement, a transition is performed to point  407 , where it is checked, whether the time T SPE  spent for collecting information is at least the time T NET  which triggers the inter-digit timer for transmission network signalling. If not, a return to point  405  is performed. 
     If it is detected at point  406  that the SC is received, a transition is performed to point  408 , where it is checked, whether information was collected at least the minimum amount needed by the service control point, i.e. nr≧min#. Point  408  can also be entered from point  407 , if the time T SPE  spent for collecting information is at least the time T NET  which triggers the inter-digit timer for transmission network signalling. If it is detected at point  408  that a sufficient number of digits was collected, a transition is performed to point  409 , where a detection point DP 2  Information_Collected is encountered. In accordance with the prior art, from point  409  the process continues by sending the collected digits to the control point and by transferring the call control to the control point. Point  409  is entered directly from point  405 , if the number of collected digits is at least the number required, i.e. nr≧max#. 
     If it is detected at point  408  that the number of collected digits is not sufficient, i.e. nr&lt;min#, the process continues from point  410 . At point  410 , a transition is made to PIC 6  of the BCSM, in which the call will be released. 
     In another embodiment in accordance with the invention the point  408  can be entered either from point  406  or from point  407  but not from both. 
     The order of points in FIGS. 3 and 4 may deviate from what has been described in the above and they may occur in parallel. In addition, other checks, such am checking of invalid information, can be carried out. Furthermore, it is possible to combine the above-described embodiments. The service switching point can be arranged to give T COL  a value which exceeds T NET  and to give min# the value zero when said service switching point receives the Collectinformation operation in which the corresponding parameter has no value. Hence the service switching point can be connected to such service control points that do not support operation in accordance with the invention. 
     FIG. 5 illustrates the service switching point SSP and its essential functions from the viewpoint of the invention. The SSP can be implemented in conventional exchanges, provided that the exchange makes a distinction between the basic call control and the IN service control. The service switching point SSP comprises an exchange terminal SSP-ET for receiving signalling from other network nodes and for transmitting signalling to other network nodes and an application part SSP-AP which controls the exchange terminal. The application part SSP-AP comprises the actual functions of the exchange, i.e, the service switching function SSF and the call control function CCF, and depending on the exchange type, possibly also the CCAF. These functions are described in greater detail in connection with FIG.  1 . The application part SSP-AP comprises a separate state model instance BCSM for each call, the BCSM being described in the above general part of the specification, and interface instances SSF-FSM (SSF Finite State Model instance). When IN service is needed, an SSF-FSM for relaying call processing instructions between the BCSM and the SCP is created for the call for an SCP connection. When the IN service is completed, the SSF-FSM will be terminated. The same state model instance BCSM may need a new IN service at some other call set-up phase, and consequently a new interface instance SSF-FSM will be created for it, The interface instances SSF-FSM related to the calls may occur in parallel and asynchronously. 
     The application part SSP-AP comprises a service switching management entity SSME for performing operations received from the IN service control point, for responding to them and for requesting instructions. The management entity SSME comprises a control unit SSME-C (SSME-Control) which maintains dialogue, on behalf of the interface instances SSF-FSM, with other parts of the switching point and other network nodes or functions, such as the service control point, of the intelligent network. It is in charge of the creation, invocation and maintenance of the interface instances SSF-FSM. The SSME-C directs the received operation to the relevant instance and creates an instance, if necessary. 
     In the first and second preferred embodiments of the invention the application part SSP-AP comprises a timer T c , for the maximum information collecting time and a memory M for storing the minimum number min# of information for comparison. In the third preferred embodiment of the invention the SSP-AP does not need the memory M for storing the minimum number of information. Correspondingly, in the fourth preferred embodiment of the invention the SSP-AP does not need the timer T c . The application part of the switching point is in charge of giving the timer T c  the value of the maximum collecting time received from the control point and/or of storing the minimum in the memory M. 
     Instead of the timer T c , the timer T SSF  of the application of the service switching point can also be employed. However, a separate timer allows more versatile operations, for instance, when sending the Collectinformation operation twice in succession, since by using the separate timer, the timer value can be set for each time separately, and if necessary, to have a different value. If the timer of the application were used, the timer value could not be changed, since according to the prior art, only one value for one operation can be given to the timer of the application. Moreover, the use of the separate timer is simpler, since according to the prior art, the Collectinformation operation transfers the SSF-FSM to a state in which the timer of the application is not used. Also other operations result in a transfer to the same state, and they do not employ the timer. 
     FIG. 6 illustrates the service control point SCP and its essential functions from the viewpoint of the invention. The SCP comprises at least a terminal part SCP-TP for receiving signalling from other network nodes and for sending signalling to other network nodes, and an application part SCP-AP which controls the terminal part. 
     The application part SCP-AP comprises at least one service logic program SLP used for providing IN services and the service control function SCF described in connection with FIG.  1 . In addition, the application part SCP-AP comprises SCF Call State Model instances SCSM. Every IN service request leads to creation of a call state model instance SCSM in accordance with the service logic program. The SCSM maintains dialogue with the SSF on behalf of the IN service logic program SLP with regard to that service of the call which resulted in creation of the call state model instance SCSM. The call state model instances SCSM related to different calls may occur in parallel and asynchronously. The application part SCP-AP additionally comprises a service control management entity SCME, which comprises a control unit SCME-C (SCME-Control), for sending operations to the service switching point. In a centralized manner the SCME-C is in charge of the dialogue of all IN-services-related instances SCSM with other parts of the control point and with other network nodes of the IN, such as the service switching point SSP and the service data function SDF. It is in charge of creating, invoking and maintaining the call state model instances SCSM. SSME-C 
     In the embodiments of the invention, the application part SCP-AP comprises a software routine which takes care that the SCSM adds to the Collectinformation operation the parameters in accordance with the invention used in the embodiment, for instance, in the first and second preferred embodiments, the parameters shown in FIG. 2; in the third preferred embodiment, only the first of the parameters shown in FIG. 2, i.e. the timer value; and in the fourth preferred embodiment, only the latter of the parameters shown in FIG. 2, i.e the minimum number. 
     It is to be understood that the above specification and the drawings related thereto are only intended to illustrate the present invention. It is obvious to the person skilled in the art that the invention can be varied and modified in a variety of ways without deviating from the scope and the spirit of the invention disclosed in the appended claims.