Method for the establishment of conference connections in a processor controlled communication system.

p0001The invention relates to a method of establishing conference connections in a communication system having a serving for its control programierbares digital computer system having at least a system memory for storing program modules and data and device-related units signalisierungsartindividuellen connection of terminals and having a coupling device for switching of the communication paths, said computer system to stored within the data base device-related information relies inter alia, permissions, services, physical functions and special device configurations concern and wherein as such a device constellation one consisting of at least one first communication terminal and a second communication terminal group is provided at least and one for the second communication terminal specific connect attempt is signaled simultaneously to the belonging to this group communication terminals and was started by the first communication terminal as a convener, a conference call with several other devices and / or official records and produced based on the input procedures of the computer system.

p0002A modern designed digital computer-controlled communications switching system basically consists of a plurality of call processing function units and a programable digital computer system that controls these functional units and monitors all switching sequences. For this purpose, the computer system with information about the operating status of the functional units and about state changes, in particular via inputs to the connected terminals, informed. It may therefore prefer to create immediate control statements and reports and output. Such communication exchanges, preferably telephone private branch exchanges are enabled in addition to the required switching controller also to control or realization of additional, beyond the actual switching operation also continuous control operations. Such additional functions are generally referred to as features, wherein a large number of different features are known in particular for the communication service "language". Such features can be introduced either in documents of the switching device or during an existing call connection. Such features include, for example, the prevention of unwanted compounds, acoustic and / or optical displayable on an optical display device instructions for each operator of a terminal in different switching-oriented states, as well as the possibility of an inquiry call to another subscriber from an existing call connection to make out. This call connection can also be a conference call, in which a participant is a connection between him and a second and at least yet produced a new participant. The conference initiating subscriber has join as convener possibility in different call states. After the aforementioned inquiry to a terminal not participating in the conference call, he can re-enter the conference and he has in increasing the authority more conferees in the conference call. It is also approved a non-return of the consultation calls in the conference call.

p0003For more connected to the communications switching system devices a particular constellation may consist in that a connect attempt is destined for a particular terminal of this group, is indicated to all other members of the group terminals simultaneously. At least two such devices this example, a chief participant and the secretary may be assigned. The terminals of these groups may be equipped with features such as those commonly used in common for so-called key telephone terminals.

p0004This means that the switching-oriented documents by connecting lines, the production of internal connections and the use of features on key activity towards. These functions are realized by integrated in the communication installation programs. The required exchange of information between the terminals and the communication system is possible by a subscriber signaling procedure in a arranged between the system and the terminals signaling channel. By about signaling information transmitted then takes the control of the visual displays that provide information on switching-oriented states of the own terminal and the other terminals of said group.

p0005The invention is based on the object of manipulations on the telephone terminal associated with conference calls for the question coming groups optimally adapt the organization of work for these relevant circumstances. In particular, this is true for at least two to each other in the described special constellation stationary terminals.

p0006This is the basis of the initially described program-controlled communications installation achieved in that in so far due to its Einberuferstatus the conference call between the remaining conferees has been transferred into the hold state from the first communication terminal, and a connection process is performed to the second communication terminal, that after this connect by pressing a special function key, due to the thus transmitted to the communication system key identification information, and due to the then read out of the associated permanent memory area of ​​the data base switching-oriented procedures by the computer control of both the triggering of the existing between the first and the second communication terminal connection as well as at the same time the transmission of a special signaling information to the second communication terminal is caused, that due to this special signaling information item automatically generates a call acceptance message, and thus the call setup procedure is initiated and thus takes the through-connection to the conference call held between the remaining terminals of the original conference participants, and in that instead of the first communication terminal to the second through the computer control of the Einberuferstatus communication terminal is assigned.

p0007As essential to the invention is to be considered that by the inventively provided special function key that set up by the first terminal conference call to the second terminal is employable without the subscriber in question need to be active with regard to the introduction of additional procedures in any way. There are for this purpose only minor expansion of the already implemented connection method required. By pressing the special function key messages are generated which cause a triggering of the differences between the two terminals current connection and at the same time generating a message in the terminal, which corresponds to the message generated at an answer in the terminal. Originally the conference call constituent terminal exits this conference call and the associated under this constellation mentioned other terminal automatically receives Einberuferstatus. Here, the relevant subscriber of any activity is optional in connection with the preparation of the transport connection with the original conferees. Through the use of microprocessors, which also includes the relocation of part of the realized in the communications system functions, in particular feature - enables and communications terminal individual input and output functions in the respective terminal, said "acceptance" message is to be generated in a very simple manner. Said particular constellation in which the inventive method is particularly useful may be, for example, executive / secretary consoles.

p0008In connection with the allocation of an established conference connection to the other terminal of compound required the preparation between the terminals may be initiated by the actuation of a corresponding line key.

p0009According to a further embodiment of the invention is storable in connection with a conference call, the reference to such a conference connection in a connection memory portion of a first dynamically allocated memory. In the processing of conventional compounds each an identifier for the communication terminals involved in a connection structure or an existing connection is stored in storage section of such a compound. The memory stored on a conference call marking refers to a portion of a second dynamically allocated at a conference call register. In these both in each case an identification of the communication terminals participating in the conference call and the address of the respective connecting portion are memory are stored by the memory controller. After preparation of the conference call by the first communication terminal the connection memory section contains as terminal-related entry an the only Einberuferstatus defining identifier of this terminal in a status characterizing this space. By assigning the conference call this identifier is deleted and replaced by the identifier of the second communication terminal.

p0010In the connection memory only three device-related messages are intended to reduce the need for the management of information einzuspeichernden programming effort. These relate, for example, the identifier for the terminals involved in a current call connection and the identifier for a terminal which is on hold. In relation to a conference connection is an extension to a space that serves for receiving an identifier for this particular conference call. By appropriately implemented control sequences is done with the allocation of conference connection to the other terminal - without the need for an additional procedure - automatically changing the information content in the one convener charaktirisierenden a conference space in the connection memory. The identifications of those terminals that are still involved in the assigned conference call, were registered as conference connection-specific data in the associated conference storage section.

p0011According to a development of the connection acting as a part of the switching network conference block is used to connect between the conference participants. It is held within the existing circuit switching possibilities for the original conference constructive communication terminal, a port to ensure a possibility of returning to the conference call available.

p0012It is thus ensured that the conceivable possibility of a return of the first terminal in the conference call in case of need can actually be accomplished.

p0013Further advantageous embodiments of the invention are disclosed in the remaining dependent claims.

p0014The invention is explained below with reference to an embodiment schematically shown in more detail.

p0015It shows<dl id="dl0001"><dt>Fig. 1</dt><dd>the logical connection to a particular device constellation in connection with a conference connection as well as basic circuit components of a digital communications system,</dd><dt>FIG. 2</dt><dd>The basic structure of the controller of such a digital communication system,</dd><dt>Fig. 3</dt><dd>The structure of a Verbindungspeicher- and conference storage portion in connection with a conference connection, </dd><dt>Fig. 4</dt><dd>a diagram with, in particular related to the mobile devices of special terminal equipment configuration messages and connecting or signaling states.</dd></dl>

p0016A central component of the schematically illustrated in Figure 1 digital communication system KA is a switching network SN via the communication devices - schematically indicated by the terminal KE, KE-A to KE-E - together or with leading to a public switching system or to other PBXs lines VL can be connected. The central switching network SN is under the control of a central plant control Ast illustrating a computer control the hierarchically highest structure level of the communications system. This structure plane is formed by a central control processor DP that coordinates the interaction of all components and modules of the communications system KA. In addition to a clock generating device PG, the system controller is further provided with an upstream access controller DCL and a memory MEM. The unit DCL is the interface to peripheral that performs as the "master" of a HDLC link protocol treatment on the signaling channel. In the memory MEM, the switching-oriented data base and all switching-relevant programs and related data are stored, for example. Essential functions of the central control process DP are therefore the storage and and the right raw execution of switching-oriented programs and the control and supervision of the local bus LB. These units DCL and the switching network SN are facing toward the periphery, connected. Additional functions of the central data processor DP example, operations-oriented workouts and dependability-oriented displays. An essential part of the periphery Pe are peripheral interfaces PS, which is associated with an interface controller LTUC. This controls the connection between the communication terminals KE, for which purpose a programmatically realized construction method is provided. In the interfaces PS with the communication terminals KE respective signaling protocols unwinding process or program modules are implemented mainly. The authorization check regarding services, feature, etc., and the connection control serving on the digital central switching network SN connection method and program modules are implemented the central system controller Ast in the memory MEM.

p0017On the communication system in addition to digital communication terminals and conventional terminals can be connected with each analog transmission via a connecting line ASL. This is done for each peripheral interface PS for the digital communication terminals via a not shown and the corresponding digital information transmission beherschende circuit module and the analog communication terminals also not shown, and appropriately adapted by one circuit module. These circuit modules are redundant for each interface PS and serve, inter alia, to convert the different signaling information from the individual terminals on a uniform used within the communications system KA format. On each circuit module each include a plurality of lead terminals are accessible.

p0018In the figure 1 more communication terminal KE-A are still to KE-E indicated, each of a, for example. two-wire subscriber line ASL are connected in the same manner as the communication terminal KE. Between the terminal equipment KE-A and KE-E a particular constellation is to be provided. These devices are intended to represent example boss / secretary participants. It is between these two devices by the operation of TL2 button on the terminal equipment KE-A, for example, represents the secretary subscriber Herstelle or key TL3 at terminal KE-E, for example, represents the chief terminal a complete connection to the respective other terminal performed. Furthermore, when a connection request to the terminal is to KE-A, this fact is signaled to both this terminal and to the specific in this constellation to stationary terminal to this other terminal KE-E. This signaling can be done at each terminal in different fashion. Thus for example the terminal KE-A, the software-defined line L1 button assigned TL1 lights and the terminal equipment KE-E could in addition to the activation of the indicator additionally be an acoustic reputation. This "pseudo line L1", therefore, rests on the two terminals. This might in principle also be the case at farther terminals. The totality of these terminals would then form a closed user group, between which connections can be established by simple keystrokes. A connection request, which is the premise of signaled on all terminals of the group can intended to a terminal, be assumed, for example, by the secretary subscriber station associated terminal KE-A.

p0019For the indicated in the figure 1 communication terminal KE-A to KE-E, which are each connected via an eg two-wire connection cable, a logical connection diagram is shown within the dashed line rimmed field, illustrating the situation with an existing conference call. The chosen symbolism is intended to indicate that a conference call with the participants of the terminal equipment KE-B was built to KE-D from the terminal KE-A. This is done via the "software line" L1, which lies at the same time at the terminal KE-E. Such multiple overlying line is referred to in the art as "Mulap" line (multiline appearance). For the terminal KE-A, it is indicated that in addition to a selection keyboard TW, the use of function keys such as a display FT DL is provided. This equipment is provided in the same way for other digital devices. These function keys can also be so-called line keys TL1 to TL3 represent, are defined via the software-assigned lines and through the actuation of a line seizure or a connection can be initiated. At least the terminal equipment KE-A and KE-E, for example, belong to a group of connected terminals are realized for the functions that are normally associated with so-called series systems. These functions are commonly referred to as key features. This means that the switching states of the rest belonging to this special group terminals are signaled on a terminal in each case when building links through the operation of one of said line-seizing keys, among others.

p0020To establish a conference call is selected by the terminal equipment KE-A from the number of the terminal device KE-B or of a synonym for stationary subscriber B. The communication system provides these two connect in a conventional manner by computer control relies on stored in the database subscriber terminal-specific data. In this context, then subscriber-related identifiers in a connection memory or into a queue memory element are stored. Subsequently is turned on in conjunction with the corresponding program modules for the setting and control of the switching network, the connection between the terminal equipment KE-A and KE-B via the switching network SN. The subscriber A goes into an inquiry call to a potential conference call partner C. The structure of the inquiry call is performed in a conventional manner. After producing this consultation call subscriber A actuates an existing on his terminal KE-A Conference button or it creates a conference call identifier, if the subscriber C wants to participate in the conference call. Because of this generated from subscriber A stimulus is through the computer control on free blocks and Conference. tested free memory sections of a conference memory. If such a block or a free conference storage section available, they will be assigned by the controller to the subscriber A, respectively. The computer controller thus provides the conference connection for the subscribers A, B and C. The inclusion of a fourth subscriber D by acting as a convener subscriber A in this conference call in the same way. Participants B to D are restored into the conference storage section and only the subscriber A remains as convener in the connection memory. Subscriber A now has the possibility the conference call he built up by pressing a special function key ST subscriber E, which is preferably a head-participants assign. This will be explained in connection with the following figures, in particular in connection with Figures 3 and 4 in more detail.

p0021The basic structure shown in Figure 2, the control of a digital communication system has a modular character and has two hierarchical levels of program control on. One of them is used by each matched to a Kommunikationsendgeräteart line technology program modules DH1, DH2 ... DHx (device handler) the control of peripheral devices. These include not only the devices connected to the peripheral communication terminals KE ... but also central line technical facilities such Anschaltesätze and routing. Each of these Leitungstechnik- program modules DH provides a unified interface system to the switching technology structure level, which is represented by a switching procedure program module CP in the present case. In the line technology structure level DH individual types of terminal equipment associated with so-called line technology program modules DTE are indicated for digital terminals and ATE for analogue terminals in the program module DH2. In the switching control structure level CP sub-modules are provided for different subtasks of call control. The exchange of information between the power technology structure level and the switching technology structure level by means of defined messages that are transmitted via a software bus structure SWB. This can be regarded as an integral part of the operating system state of the communications switching system computer. The switching control program module CP, the Leitungstechnik- program modules DH1, DH2 ... DHx and the software bus SWB have DBAR access to database DB of the entire communication system by means of data base access routines. In addition to the switching procedure program module CP further modules are provided, one of which with AMA for example, the administration and maintenance program modules are indicated. These are used for the processing of operational tasks. At least a part of them is also via defined database access routines, the database DB accessible. The line technology program modules DH1, DH2 ... DHx formed communications terminal to species so that they each control the signaling method and the user interface of the corresponding kommunikationsendgeräteart. The switching procedure program module CP's communications terminal types independently and communications services independently such structured that it dominates the maximum functional peripheral equipment and supplies control technology. The duties of the switching procedure program module CP and so necessary for the control of connection establishment and the disconnect sub-processes of the whole switching procedure. For example, are tested and performed dial controls permissions. There is also a signaling of switching-states between the communication terminals, and it is an enabling and disabling of switching technology performance features from the different switching-oriented states out feasible.

p0022An essential part of the switching technology structure level CP is the switching procedure program module CPTL (call processing trunk line) which is in turn divided into not shown different submodules. The switching-oriented control procedures are performed by a schematically illustrated in Figure 2 within the unit CPTL processor DP of the central computer control. Representing the measures provided for in the system performance feature program modules the LM module is shown. To the performance feature program modules is also a network control program module NWC to count, with the entire logical connection memory controller and the controller of the switching network SN is realized. Furthermore, a unit CON is provided, which indicates the feature "conference connections". The dashed in the Figure 2 illustration of this unit CON expresses that the feature for "leadership conference connections" does not require a separate performance feature program module, but is performed on the basis of the implemented in the communication system standard switching procedures. By block SN within the network control program module NWC is indicated that so that the control of the switching network SN and the control of existing as part of this switching network conference blocks KON-S is realized.

p0023The data base DB, which is for example allocated to the memory MEM of the control branch comprises permanent memory. In memory area KD system configuration information SK are stored for example as permanent data. This relates to one another and the Customized fixed allocation of the individual connected to the communications system KA terminals KE. For example, the information about the possibility for terminals KE-A and KE-E special constellation as boss / secretary call stations is stored. Basically, a unit of each associated storage area is requested each initiate a connection establishment procedure by a communication terminal in this customer data memory KD of the database. As part of this query the calling communication terminal is uniquely identified. The stored therein services and privileges in terms of usable features are read and, if necessary in a dynamic data-storing memory area AS stored the database. At the same time, the physical features contained therein, such as read and stored as the terminal interfaces used. These data are evaluated or interrogated in the course of the connection setup and initiate call processing procedures. Furthermore KD information contained, inter alia, with respect to the line-seizing function keys in the permanent storage area. A function key is also used in the invention special function key ST, which is present at the terminal KE-A and their meaning will be described later. In the permanent storage area FTI keys identification data are stored, for example. Furthermore, the fact that information from which to be introduced due to a key operation switch Technical procedures are removably stored. Preliminary, the stored key identification data with those data are compared, which were formed by pressing a function key the respective communication terminal and transmitted to the communication system. By operating such a button on a communication terminal, which are associated with the so-called key functions, so it can be assigned directly its own cord through the communication system, it may be the terminal connected to a trunk line connected to the communication system or a connection to another internal communication terminal be performed. In the space reserved for the terminal-related information permanent memory area KD is as already mentioned on this day, then, that the special terminal equipment configuration KE-A and KE-E is controlled by the so-called "Mulap" line L1. This stored information then yield the same time an indication of the switching-oriented procedures coupled thereto. In this particular case, this means among other things that an incoming call to the two terminals is signaled.

p0024For dynamic data of the storage area AS is provided in the database DB, said storage area may be a memory of the memory device MEM of the system control Ast. For each incoming call or each time you connect a dynamic memory section VSS is assigned a connection memory VS the compound. In connection with the connection even more storage elements are used, which serve as so-called queue elements of a queue memory WS. In connection with a conference call, a conference memory KS is further used, in which the individual memory sections KSS conference connection-specific data is written.

p0025For the indicated in Fig. 1 within the dashed line indicated field conference connection situation between the total of participating terminals KE-A to KE-E enrolled by the system controller in the memory sections of a connection memory and a conference memory information in Figures 3a to 3d are illustrated structurally. It is assumed that the terminal equipment KE-A (Secretary-station) from a conference with participants B to D through their associated terminals KE-B was built to KE-D in the manner described above in connection with the figure 1 , For this purpose, a connection memory section VSS1 a connection memory was allocated. In such a connection memory are only three the terminals involved defining entries added to minimize the Programieraufwand inter alia for the administration of this compound storage principle few example. It is, for example, an identifier for the terminal equipment or participants currently involved in a call connection and the identification of an in hold state further participant provided. This identifier can refer each containing a specific information device memory element. In such a device memory element that is associated with each participant Additional information is contained, for example, contains its connection status and address information for memory locations in which subscriber-related data can be found. The compound storage section VSS1 in the figure 3a contains a subscriber-related identification only the identifier CSR-A for the terminal KE-A or to the subscriber A. In addition, the memory section VSS1 a location for an identifier of a conference call. This space is denoted in the figure with Conf-INDX. 'X' can be between 1 and 'm', where 'm' is equal to the maximum number of made available to end conference storage sections KSS corresponds a conference memory. As conference Index Conf-INDxist unrecorded know the full address of a competent conference storage portion but only an index number 1 to 'm' as this the necessary storage space is reduced. The conference Index is in an address Ad converted, thereby, the respective Conference storage section KSSx fixed. While in the compound storage section VSS1 only the identifier for the convener of the conference call is included, the identifiers for the other party to the conference call devices or subscriber in the conference storage section KSSx a conference memory KS are included. In the exemplary embodiment, these are the identifiers for the subscriber B to D. From the order number given in the conference Index ie the address of the dynamic respectively associated conference storage portion can be determined so that, where appropriate, the identifiers for other conferees are storable.

p0026Furthermore, in such a conference section of memory is associated with each conference call, an identifier ad VSS1 contain the connection memory, in which A is entered, the conference initiating subscriber. In "Conference storage section" KSSx can further compound typical data such as the number of participants involved in the betreffenen conference call, the number of trunk groups participating in the conference call - be stored - as far as the external participants were taken into a conference. So there are in all enrolled in a specific conference call descriptive data.

p0027In the figure 3b, the connection state is shown in which on a software-defined line L2 / L3 connection to the to the stationary in a particular partner constellation device KE-E is constructed from the terminal KE-A, and this unit is called. Whenever a calling party information is making a connection attempt to a target subscriber enrolled in an element of a WS queue memory. In this element, which is the address of the connection memory VSS2 is registered, which was provided for the initiated call between the subscribers A and E. Furthermore, this queue element WS contains an identifier of a code point KZPE. Such a code point is set as the identifier for each "unit" which is to be selected via the system. Such labeling is thus defined for each terminal, for each office set and example for radio paging equipment and also for the so-called "Mulap" line.

p0028In the original conference call associated connection memory portions VSS1 only conference index and the identifier KZPA is listed on the measure point of the terminal A. In this space concerned so the quasi absent convener of the original conference is still being held. So then you have the possibility the line L1 trigger if it require special connection states. Ov it this code point of the convener obtains a reference to the memory entry in the data base of than that of the relevant line button associated line - identifies "Mulap" line L1. Furthermore, it is by this point the figure for the subscriber A the opportunity to a certain extent by his original in a holding state Guided conference call re-enter. Marks registered in the storage section conference participants are still in conference-call status, meaning they have the ability to talk to each other without restriction.

p0029The 3c shows the connection state, in which the subscriber E has reported. In this state of connection, the entries in the connection memory VSS1 and meeting memory section KSSx are compared with entries contained in the figure 3b in the memory sections concerned, remained unchanged. In the compound storage portion VSS2 the interlocutor E is additionally marked. This is done by the identifier stored therein CSR-E to the subscriber E. The entries in the queue element is deleted.

p0030In Figure 3d shows the situation after the special function key ST is pressed during the call connection between the subscriber A and the subscriber E by the participant A. then the sequences or messages shown in Figure 4 are initiated By pressing this special key. result will be described later on this to the subscriber automatically enters E without any additional manipulations on his terminal in the between participants B through D still existing conference call. With this admission him the Einberuferstatus is assigned simultaneously. This is determined by the fact that it is stored in the link storage section VSS1 with its identifier instead of the previously contained therein subscriber A. Subscriber A has left the conference call and will be triggered. It is therefore no longer in the call register.

p0031The other party to the conference participant B to D are still stored in the memory section conference KSSx.

p0032In the figure 4 those messages are illustrated with respect to the terminals, and in particular the terminal KE-A and KE-E, which are generated, inter alia, in the call processing structure level LDU-CP. It also sets the switching-oriented status of the individual devices are defined. Furthermore, the signaling made to the terminal equipment KE-A and KE-E and produced in these devices and the switching-oriented structure level LDU CP are shown transmitted messages.

p0033Figure 4 is divided in the sub-figures 4a and 4b. It is initially assumed that the subscriber A has built up in the already described manner, a conference call with subscribers B to D, and therefore there is a call between all of these participants. In this conference call subscriber A has the Einberuferstatus. So he can against the other participants, which can emerge only from the conference call by hanging up their handset additional features, take for example, the inquiry call to another subscriber and re-entering this conference call to complete. This call connection could also take place between at conference links were to be involved participants. This concerned participants are then stored in the database. Such a conference connection with specified group of participants could be initiated by pressing a button on the conference participant terminal of the subscriber A. The computer system then checks automatically the connection status of the remaining firmly provided for this conference call participants and provides the conference connection with those participants who are in the free state.

p0034At terminal KE-A, the line L1 is as busy and the line L2 signals as free. During the existing conference call will produce E by the subscribers A key TL2 actuated to connect to the subscriber.

p0035From this, a message is first derived, which causes the switching procedure program module, the line L1 - that is, the other participants in the conference call based on subscriber A - placed in a holding position. The call between the other participants B through D of the original conference connection remains. It is VSS1 (Figure 3) and the "Mulap" line L1 in a queue memory element, as well as marking the conference call made the Einkettung the connection memory than last held call. The switching technology generates a hold request. Then KE-A is at the terminal, the line L1 indicates the line on hold and there is a message that causes the transition in this holding position for the conference participants. The requirement in the terminal equipment KE-A formed with the operation of the line key TL2 for the AC line to which the connection to the subscriber e-enabling "software" line L2, then performs the involvement of the line technology program module DH-A to connect attempt on the intercommunication between the participants A and e specified lead L2. A corresponding Charaktirisierung in permanent memory KD the database DB (Figure 2) can be generated automatically dialing information for the connection request to the subscriber E. At terminal KE-A objectified in the form of a line key TL2 line L2 is marked as occupied. From the switching technology structure level, the request for the connection of the ring signal for the terminal equipment KE-E takes place. On this terminal, the signaling with respect to the line L3 is changed so that the call status is displayed. Due to the successful in the terminal message about the connection acceptance, which is fed via the line technology program module DH-E the call processing module LDU CP, a message that pulls the switching of the connection between L2 and L3 to be. Thus, it relates to a connection between the terminals KE-A and KE-E. The line L3 is signaled on the terminal equipment KE-E as occupied. The "pass-through" simultaneously causing the hitherto applied ringing signal is switched off for the terminal KE-A.

p00364b shows the messages and signaling or line states are shown by the place during the conversation condition between the subscriber A and the subscriber E pressing the special function key ST at terminal KA - start - for example the secretary terminal. The operation of this special function key ST is transmitted by means of the message TID via the line technology structure level of the switching technology structure level. Then, it is determined by checking that the terminal of the current call partner E rests the "Mulap" line L1. Then, both a message "release" to the line technology program module DH-A as well as a message "special" STS is transmitted to the line technology program module DH-e and transmitted to the respective terminal. In each relevant line technology program module to adapt the individual messages to the sum earmarked for the terminal message format is made then optionally. Such adjustment shall be made for messages to be transmitted from one terminal to the switching technology structure level.

p0037With the message "triggering" a release operation for existing between the terminal equipment KE-A and KE-E connection is initiated. It is in this case transmitted by the message "trigger" in the reverse direction of the line technology structure level DH that the respective terminal has responded. This message can generally also be used to turn off pathways and sounds. After the firings, the free state for the "pseudo lines" L2 and L3 reached and signals this fact to the terminal equipment KE-A and KE-E. The line L2 or L3 is thus marked as "free." Besides these firings STS is the same basis of the transmitted special message "special status" generates a message corresponding to that as an acceptance message that is generated when a call is accepted. This is due to the special state in which the "Mulap" line 11 stands and this terminal than this message "special status" STS has been submitted. Although Comes in this specific condition the message "Triggering Partner E", then as already described the current connection L2, L3 triggered, but it is also the mentioned "acceptance" message will be generated with respect to the line L1. At terminal KE-E, the line L1 is signaled as busy. Due to the "acceptance" message queue memory is searched by the controller after the entry KZPE, so the code point of the terminal KE-E that matches its label marked "Mulap" line. If the entry is found, so is thus the address of the connection memory VSS1 known because this address is also included in the queue memory element as a reference. In this connection competent memory VSS1 is then in those space in which an identifier for the subscriber A was originally stored, enrolled the identifier for the subscriber e. This special space is then in the same time that this participant receives the convener status for the conference E. With a generated in the switching-oriented program module LDU CP Belegtmelduung for "Mulap" line L1, this line will be signaled to the terminal equipment KE-A and KE-E as occupied. By switching equipment takes place a program calling for the review of the connection memory to see if it the conference Index Conf-IND is registered. If so then found in the embodiment that the connection memory VSS1 such a conference Index is registered, can be inferred from the fact that participants are to be joined for a conference. The reference to the standing in the connection memory VSS1 index the address of the associated conference storage portion KSSx is known, so that it the command for switching through the subscriber B is performed to D and E of the participant as a convener to the conference call. By pressing the special function key ST on the terminal of the original convener A, whose effects can be described as Zuweistaste is therefore with a slight expansion by special program units, - which essentially relate to the generation of the message accepting - the conference call between the participants E and the already standing in the conference call participants BD conveys.