KR20080006188A - Method and system for providing coloring back tone service - Google Patents

Abstract

A CRBT(Color-Ring Back Tone) service supply system and a method thereof are provided to enable a CRBT server to be located on a rear end of a PBX(Private Branch Exchange), therefore an extension terminal connected to the PBX can make calls even in case of down or stopped. A telephone office(100) transmits a receiving call received from a central office terminal to a PBX(300), and transmits a CRBT to the central office terminal. When the receiving call is received, the PBX(300) demands a CRBT to a CRBT server(200) connected by a PRI(Primary Rate Interface), and transmits the CRBT to a sending terminal. The CRBT server(200) stores plural sound sources for providing as CRBTs, and transmits a sound source corresponding to the CRBT demand received from the PBX(300) to the sending terminal through the PBX(300).

Description

System for providing ring back tone service and method thereof {method and system for providing COLORing Back Tone service}

1 is a block diagram illustrating a private exchange system providing a general ring back tone service.

2 is a block diagram illustrating a system for providing a ring back tone service according to the present invention;

3 is a block diagram illustrating a private exchange in accordance with a preferred embodiment of the present invention.

4A is a diagram for explaining the structure of a setup message among general PRI messages.

4B is a diagram for explaining the structure of a setup message according to the present invention;

4c is a diagram for explaining the structure of a ring back tone IE field according to the present invention;

5 is a block diagram illustrating a CRBT server according to a preferred embodiment of the present invention.

6 is a flowchart illustrating a flow of a ring back tone providing service according to a preferred embodiment of the present invention.

7 is a flowchart illustrating a flow of a ring back tone providing service according to a second preferred embodiment of the present invention.

8 is a flowchart illustrating a method for providing a ring back tone service according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: telephone station 200; CRBT server

210: DPM board 220: sound source

230: control unit 240: database

300: private exchange 310: trunk board

320: E1 board 330: subscriber card

340: storage unit 350: switching unit

The present invention relates to a system for providing a ring back tone service and a method thereof.

Today, in response to the development of communication and electronic technologies and various service needs of subscribers, a ring tone service is provided.

In addition, a private exchange system using a private branch exchange (PBX), in which all employees share a certain number of external telephone lines and uses them for the purpose of cost reduction, is widely used.

1 is a block diagram illustrating a private exchange system for providing a general ring back tone service.

Referring to FIG. 1, a CRBT (COLORing Back Tone) server 30 providing a ring back tone with the telephone company 10 is connected to the E1 line, and is connected to the EBT line of the CRBT server 30 and the private exchange 20. . In other words, the CRBT server 30 is located between the telephone station 10 and the private exchange 20.

In addition, the CRBT server 30 includes a plurality of signal processing boards 21 that match the E1 line, and stores a sound source 22 for providing a ring back tone.

The private exchange 20 has a trunk board 31 capable of matching with the E1 line and a subscriber card 32 connected to a plurality of extension terminals 40.

Such a method of providing a ring back tone service of a private switching system will be briefly described.

When the telephone station 10 receives the call request signal (incoming call), it transmits the incoming call to the private exchange 20 via the CRBT server 30 located between the private exchange 20 and the private exchange 20. Switches the incoming call to the extension terminal 40.

At this time, the CRBT server 30 transmits a ringback tone, that is, a ring back tone, through the telephone station 10 to the calling terminal using the stored sound source 22.

However, the CRBT server 30 is located between the private exchange 20 and the telephone station 10, that is, the CRBT server 30 is located at the end of the trunk line (E1 line) coming from the telephone station 10, and then again. In the method of connecting the CRBT server 30 and the private exchanger 20 from the E1 line, if the CRBT server 30 is down or a problem occurs in the function of the CRBT server 30 due to hacking, virus infiltration, etc., the private exchanger The connection between the 20 and the telephone station 10 becomes impossible, and thus the extension subscribers of the private exchange 20 become incapable of talking.

In addition, when the calling terminal dials the telephone station 10, the telephone station 10 and the CRBT server 30 perform the E1 SIG SFring through the E1 line, and then the CRBT server 30 and the private exchange 20 perform the E1 line. Since E1 signaling must be performed through the line signaling process, only two times of the line signaling process are performed, and the time required for transmitting the incoming signal to the called party is increased by transmitting the incoming signal from the extension terminal 40 (the called party).

In addition, the plurality of extension terminals 40 connected to the private exchange 20 do not use the ring back tone service when making an extension call.

Accordingly, the present invention was devised to solve the above problems, and even if the CRBT server is down or the function is stopped, an extension terminal connected to a private exchange can make a call and minimize the time for an incoming call to the called party. An object of the present invention is to provide a ring back tone service providing system and a method thereof.

Another object of the present invention is to provide a ring back tone service providing system and method capable of providing a ring back tone to an extension terminal connected to a private exchange, and can provide different ring back tones for each caller and called party.

The system for providing a ring back tone service according to an aspect of the present invention for achieving the above object is a telephone station for transmitting an incoming call received from a trunk line terminal to a private exchange, and for transmitting a ring back tone to a trunk line terminal, and a telephone station and a trunk line. When connected, and connected to a plurality of extension terminals, when an incoming call is received, requesting a ring back tone to the CRBT server connected to the PRI interface, and a private exchange for transmitting the ring back tone to the calling terminal, a plurality of to provide a ring back tone It stores a sound source, CRBT (COLORing Back Tone) server for transmitting a sound source corresponding to the ring back tone request received from the private exchange to the calling terminal through the private exchange.

The private exchange according to the present invention includes a trunk board connected to a telephone station through a trunk line, an E1 board connected to a CRBT server through a PRI interface, a subscriber card connected to a plurality of extension terminals, an outgoing call number or And a storage unit for storing a ring back tone IE according to the called phone number, and a switching unit for setting a plurality of extension terminals and trunk line communication paths connected through a subscriber card or setting an extension path between extension terminals.

The switching unit according to the present invention includes a message processing unit for transmitting a setup message including a ring back tone IE according to an outgoing call number or an incoming call number of an incoming call to a CRBT server.

The ring back tone IE according to the present invention may include at least one of a caller group information of an incoming call, an outgoing call number, a caller group information indicating that a caller terminal is a trunk line or an extension terminal, or a caller group information to which a called terminal belongs. Include.

The message processing unit according to the present invention generates the setup message by including the ring back tone IE in the setup message of the message flow of the PRI interface.

The setup message according to the present invention includes a Sending complete IE field, a Bearer capability IE field, a Channel identification IE field, a Calling party number IE field, a Called party number IE field, and a ring back tone IE field, and the ring back tone IE field includes outgoing information. (Calling Party Sub-IE) field and Called Party Sub-IE.

The calling information according to the present invention includes a Calling Party Information Sub-IE field, a Calling Party content Length field, a Class Of Service field, a Tenant field, a Group Type field, a Group number field, and a Tel number field. Sub-IE field, Called Party content Length field, Class Of Service field, Tenant field, Group Type field, Group number field, Tel number field.

When the CRBT server according to the present invention receives a setup message requesting a ring back tone from the private exchange, the CRBT server transmits a sound source corresponding to the ring back tone IE included in the setup message to the calling terminal through the private exchange.

The CRBT server according to the present invention is connected to a private exchange and a PRI interface, and includes a DPM board for grasping a ring back tone IE included in a setup message, a database storing a plurality of sound sources, and a ring back tone IE grasping the DPM board. And a control unit searching for a sound source corresponding to the database and transmitting the same to a calling terminal.

The control unit according to the present invention, if the caller group information of the ring back tone IE is a trunk line terminal, provides the ring back tone according to the company advertisement sound source to the call terminal, and if the extension terminal, transmits the ring back tone according to the company known sound source to the call terminal. .

The control unit according to the present invention transmits the ring back tone according to the announcement sound source for each department according to the called party group information of the ring back tone IE to the calling terminal.

According to another aspect of the present invention, there is provided a method for providing a ring back tone service, the method comprising: checking whether a call originating terminal of an incoming call received by a private exchange is a trunk line terminal or an extension terminal; Transmitting a setup message including the IE to the CRBT server, and transmitting a ring back tone corresponding to a sound source corresponding to the ring back tone IE included in the setup message received by the CRBT server to the calling terminal through the private exchange. do.

The step of transmitting the ring back tone to the calling terminal according to the present invention, if the caller group information of the ring back tone IE included in the setup message is the CO line terminal, the CRBT server transmits the ring back tone according to the recall advertising sound source to the CO line terminal, the extension If the terminal, the ring back tone according to the company-known sound source is transmitted to the extension terminal.

The step of transmitting the ring back tone according to the present invention to the calling terminal, transmits the ring back tone according to the announcement announcement for each department corresponding to the caller group information of the ring back tone IE to the extension terminal.

The method for providing a ring back tone service according to the present invention comprises the steps of: connecting, by a private exchange, a call path for an incoming call while requesting a disconnection from the CRBT server when the called terminal answers the incoming call; If disconnection is requested, the method further includes disconnecting from the private exchange while stopping transmission of the ring back tone.

Hereinafter, a system and method for providing a ring back tone service according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram illustrating a system for providing a ring back tone service according to the present invention.

2, in the system for providing a ring back tone service according to the present invention, a telephone station 100 and a private exchange 300 are connected to an E1 line, and the private exchange 300 and the CRBT server 200 are PRI (Primary Rate Interface). in ISDN) interface. That is, the telephone station 100 is connected to the front end position of the private exchange 300, and the CRBT server 200 is connected to the rear end position.

The private exchange 300 is a trunk board 310 connected to the telephone station 100 through an E1 line, a subscriber card 330 connected to a plurality of extension terminals, and an E1 board connected to the CRBT server 200 through a PRI interface. It is provided with a 320, CRBT server 200 stores a plurality of sound sources 220 to be provided as a digital process module (DPM) board 210 and the ring back tone connected to the private exchange 300 through the PRI interface do.

The telephone station 100 transmits the incoming call to the private exchange 300 through the E1 line when the incoming call is received from the calling terminal (copier line terminal) whose telephone number is the telephone number assigned to the private exchange 300.

The private exchange 300 identifies the ring back tone information element (IE) corresponding to the incoming call received through the trunk board 310, and the ring back tone request message including the ring back tone IE (hereinafter referred to as a "setup message"). To the CRBT server 200.

That is, since the private exchange 300 is connected to the CRBT server 200 through the PRI interface, the private exchange 300 may transmit a ring back tone request message using a setup message during the PRI message flow.

The private exchange 300 transmits a ring back tone IE (Information Element) corresponding to the incoming call to the CRBT server 200, and the ring back tone IE includes a called telephone number, an outgoing telephone number, a calling party group or a called party group. do.

 The caller group specifies whether the caller group is an extension call for an extension call or a CO line call for a trunk line call.

3 is a block diagram illustrating a private exchange in accordance with a preferred embodiment of the present invention.

Referring to FIG. 3, the private exchange 300 of the present invention includes a trunk board 310, a subscriber card 330, an E1 board 320, and a switching unit 350, and the switching unit 350 includes a message processing unit. 360.

The trunk board 310 is connected to the telephone station 100 through the E1 line (co-op line), and receives an incoming call or transmits the incoming call to the telephone station 100 when the extension terminal requests a call.

In addition, the trunk board 310 transmits a call connection sound corresponding to the sound source 220 provided from the CRBT server 200 to the calling terminal connected to the trunk line.

The E1 board 320 is connected to the CRBT server 200 through the PRI interface, and transmits a setup message generated by the private exchange 300 to the CRBT server 200 or receives a ring back tone from the CRBT server 200. In addition, the subscriber card 330 provides the extension terminal or the trunk line terminal as the calling terminal.

The subscriber card 330 is connected to a plurality of extension terminals 400, and connects a call with a trunk line terminal through a call connection or a trunk line for an extension call between each extension terminal 400. In addition, the subscriber card 330 provides the ring back tone provided from the CRBT server 200 to the extension terminal 400.

The storage unit 340 stores the ring back tone IE according to the incoming call number or the outgoing call number of the incoming call.

That is, the storage unit 340 stores the calling party group information, the called party group information, etc. of the incoming call, and the calling party group information and the called party group information are information for making the ring back tone different for each caller or each callee.

When the incoming call is received from the CO line terminal, the caller group information is the CO line call. In the case of the extension terminal 400, the caller group information is the extension line.

In addition, the called party group information divides the called telephone number of the called party into groups. For example, a plurality of called parties can be divided by department or team.

The switching unit 350 connects the call according to the incoming call received through the trunk line with the extension terminal 400 which is the called terminal, or switches the call for the extension call between the extension terminals 400.

The message processor 360 of the switching unit 350 transmits a setup message including the ring back tone IE corresponding to the incoming call to the CRBT server 200.

According to an example, when the outgoing call number of the incoming call is the trunk line terminal, the message processing unit 360 includes the caller group information, the call line outgoing call, the caller group information corresponding to the incoming call number, and the outgoing call number and the incoming call number. Sends a setup message that includes the to the CRBT server (200).

On the other hand, the message processing unit 360, if the incoming call number of the incoming call is the extension terminal 400, the caller group information is the extension call, and includes the caller group information corresponding to the incoming call number, the outgoing call number and the incoming call The setup message including the telephone number is transmitted to the CRBT server 200.

4A is a diagram for explaining the structure of a setup message among general PRI messages.

Referring to FIG. 4A, the setup message includes a Sending complete IE field, a Bearer capability IE field, a Channel identification IE field, a Calling party number IE field, and a Called party number IE field.

Hereinafter, the description of each field of the PRI message is described in detail in the 'Q.931' protocol, and thus the detailed description is omitted. 'Q.931' is an access control protocol of an integrated services digital network (ISDN).

4B is a diagram for explaining the structure of a setup message according to the present invention.

As shown in FIG. 4B, the message processing unit 360 according to the present invention generates a setup message by adding a ring back tone IE field in which a ring back tone IE according to an incoming call is specified to a general setup message.

The ring back tone IE field may be divided into outgoing information and incoming information.

4c is a view for explaining the structure of the ring back tone IE field according to the present invention.

As shown in FIG. 4C, the ring back tone IE field may be divided into a calling party sub-IE and a called party sub-IE.

The calling information includes a Calling Party Information Sub-IE field, a Calling Party content Length field, a Class Of Service field, a Tenant field, a Group Type field, a Group number field, and a Tel number field. Includes IE field, Called Party content Length field, Class Of Service field, Tenant field, Group Type field, Group number field and Tel number field.

Here, the Class OF Service field specifies the service level of the caller or called party, and the Group type and the Group Number specify caller group information or called party group information of the caller or called party.

For example, the Group type of the calling information specifies whether the caller is the extension terminal 400 or the trunk line terminal, and the Group Number of the incoming information specifies the group (per department) in which the called party is included.

In addition, the switching unit 350 transmits the setup message to the CRBT server 200, and then the call terminal tones according to the sound source 220 provided from the CRBT server 200 according to the calling information of the extension terminal 400 or the trunk line terminal. To ringback tone.

The CRBT server 200 grasps the ring back tone IE included in the setup message received from the private exchange 300, and provides the sound source 220 according to the call information and the incoming call information as the ring back tone.

5 is a block diagram illustrating a CRBT server according to a preferred embodiment of the present invention.

Referring to FIG. 5, the CRBT server 200 according to the present invention is connected to a private exchange 300 through a PRI interface, and grasps the ring back tone IE included in the setup message received from the private exchange 300 to control the controller ( DPM board 210 to be transmitted to 230, various types of sound source 220 to be provided as a ring back tone, database 240 and DPM board 210 is stored, the sound source information corresponding to the ring back tone IE is set up And a controller 230 for providing a sound source 220 corresponding to the ring back tone IE identified from the message as the ring back tone.

Here, the DPM board 210 corresponds to a digital voice processing board that processes signaling through the private interface 300 and the PRI interface, and the control unit 230 may provide a ring back tone to the central processing unit (CPU). It can be driven by mounting the application.

The controller 230 checks sound source information corresponding to the ring back tone IE received from the DPM board 210, and provides the corresponding sound source 220 to the private exchange 300 as the ring back tone.

For example, if the caller group information included in the setup message is the CO line transmission, the controller 230 transmits the company advertisement sound source 220 among the sound sources 220 stored in the database 240 to the CO line terminal as a ring tone, If the extension terminal 400, the company announcement sound source 220 is transmitted to the extension terminal 400 as a ring tone.

On the other hand, the control unit 230 may transmit a different ring back tone to the calling terminal according to the called party group information of the call ring tone IE, for example, the call set terminal (department announcement) of the corresponding department according to the called party group information To send.

6 is a flowchart illustrating a flow of a ring back tone providing service according to a preferred embodiment of the present invention.

Referring to FIG. 6, a case in which the originating terminal is a trunk line terminal will be described. When the incoming telephone number of an incoming call received from the originating terminal is the private exchange 300, the telephone station 100 transmits an incoming call to the trunk line (E1 line). Through the private exchange 300 through (HOF) (S 100).

When the private exchange 300 receives an incoming call from the telephone company 100, the private exchange 300 transmits a setup message including the ring back tone IE corresponding to the incoming call to the DPM board 210 of the CRBT server 200 (S 110).

At this time, the ring back tone IE includes caller group information, called party group information of the incoming call.

The DPM board 210 of the CRBT server 200 grasps the ring back tone IE included in the received setup message and transmits the call back tone playback message to the control unit 230 of the CRBT server 200 (PLAY_START) (S 120). ).

At this time, the DPM board 210 does not transmit a response message (ALERT or ANSWER) to the private exchange 300 in response to the setup message received from the private exchange 300.

The control unit 230 checks the sound source information corresponding to the ring back tone IE received from the DPM board 210, and transmits the sound source 220 to the private exchange 300 through the DPM board 210 as the ring back tone ( S 130, 140).

The controller 230 may provide a ring back tone according to the company advertisement sound source 220 to the trunk line terminal since the calling terminal is a trunk line terminal.

The private exchange 300 transmits the ring back tone received from the CRBT server 200 to the trunk line terminal which is the calling terminal (S 150).

When the extension terminal 400 which is the called terminal connected with the private exchange 300 is hooked off (S 160), the private exchange 300 transmits a connection termination request message to the DPM board 210 of the CRBT server 200 ( DISCONN) (S 170).

When the connection termination request message is received, the DPM board 210 transmits a call connection tone stop message to the controller 230 (PLAY_STOP) (S 180).

When the call ring tone stop message is received from the DPM board 210, the controller 230 stops playing the call ring tone.

The private exchange 300 connects the call path between the trunk line terminal and the extension terminal 400 while transmitting the connection termination request message to the CRBT server 200 (S 190).

In addition, the DPM board 210 requests release of the connection connected to the private exchange 300, that is, the connection for transmitting the ring back tone, while transmitting the call ring tone stop message to the controller 230 (RELEASE) (S200).

When the private exchange 300 receives a release request from the DPM board 210, the private exchange 300 transmits a confirmation message to the DPM board 210 while releasing the connection (REL_COMP) (S 210).

7 is a flowchart illustrating a flow of a ring back tone providing service according to a second embodiment of the present invention.

Referring to FIG. 7, the case where the calling terminal is the extension terminal 400 will be described. The extension terminal 400 transmits an incoming call to the private exchange 300 according to the selection of the extension subscriber (HOF) (S 300). ).

When the private exchange 300 receives an incoming call from the extension terminal 400, the private exchange 300 transmits a setup message including the ring back tone IE corresponding to the incoming call to the DPM board 210 of the CRBT server 200 (S 310).

At this time, the ring back tone IE includes caller group information, called party group information of the incoming call.

The DPM board 210 of the CRBT server 200 grasps the ring back tone IE included in the received setup message and transmits the call back tone playback message to the control unit 230 of the CRBT server 200 (PLAY_START) (S 320). ).

At this time, the DPM board 210 does not transmit a response message (ALERT or ANSWER) to the private exchange 300 in response to the setup message received from the private exchange 300.

The control unit 230 checks the sound source information corresponding to the ring back tone IE received from the DPM board 210, and transmits the sound source 220 to the private exchange 300 through the DPM board 210 as the ring back tone ( S 330, 340).

Since the calling terminal is the extension terminal 400, the control unit 230 may provide a call connection sound according to the company announcement sound source 220 or the departmental announcement sound source 220 to the extension terminal 400.

The private exchange 300 transmits the ring back tone received from the CRBT server 200 to the extension terminal 400 which is the calling terminal (S 350).

When the extension terminal 400 which is the called terminal connected to the private exchange 300 is hooked off (S360), the private exchange 300 transmits a connection termination request message to the DPM board 210 of the CRBT server 200 ( DISCONN) (S 370).

When the connection termination request message is received, the DPM board 210 transmits a call connection stop message to the controller 230 (PLAY_STOP) (S380).

When the call ring tone stop message is received from the DPM board 210, the controller 230 stops playing the call ring tone.

The private exchange 300 connects the call path between the trunk line terminal and the extension terminal 400 while transmitting the access termination request message to the CRBT server 200 (S390).

In addition, the DPM board 210 requests release of the connection connected to the private exchange 300, that is, the connection for transmitting the ring back tone, while transmitting the call ring tone stop message to the controller 230 (RELEASE) (S 400).

When the private exchange 300 receives a release request from the DPM board 210, the private exchange 300 transmits a confirmation message to the DPM board 210 while releasing the connection (REL_COMP) (S410).

Therefore, the call connection sound service may be provided even when the calling terminal is not only the trunk line terminal but also the extension terminal 400.

8 is a flowchart illustrating a method of providing a ring back tone service according to an exemplary embodiment of the present invention.

Referring to FIG. 8, the private exchange 300 receives an incoming call from the calling terminal (S 500).

The private exchange 300 checks whether the incoming call is received from the trunk line terminal or the extension terminal 400 (S 510).

The private exchange 300 transmits a setup message including the ring back tone IE for the incoming call to the CRBT server 200 (S520).

In this case, the call connection sound IE included in the setup message is, if the originating terminal of the incoming call is a trunk line terminal, the caller group information is a trunk line terminal, and includes the called party group information corresponding to the incoming terminal of the incoming call, or the incoming call is the extension terminal 400. Caller group information is the extension terminal 400, and the caller group information is included.

The DPM board 210 of the CRBT server 200 grasps the ring back tone IE included in the setup message received from the private exchange 300, and requests the controller 230 to play the ring back tone corresponding to the ring back tone IE ( S 530).

The controller 230 transmits the ring back tone according to the sound source 220 corresponding to the ring back tone IE to the trunk line terminal or the extension terminal 400 which is the originating terminal through the private switch 300 (S540).

According to an example, if the caller group information of the ring back tone IE is a trunk line terminal, the control unit 230 provides a ring back tone according to the company advertisement sound source 220, and if the caller group information is the extension terminal 400, the company announcement or department Provides a ring back tone according to the announcement sound source (220).

When the terminating terminal hooks off while transmitting the incoming call to the terminating terminal, the private exchange 300 requests the CRBT server 200 to terminate the connection and connects the call path for the incoming call (S550).

When the connection termination request is requested, the DPM board 210 of the CRBT server 200 releases the connection with the private exchange 300 while requesting the control unit 230 to stop the ring tone (S560).

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and changes are possible within the technical spirit of the present invention, and such modifications and modifications belong to the appended claims.

As described above, according to the present invention, since the CRBT server is located at the rear of the private exchange, the extension terminal connected to the private exchange is able to make a call even if it is down or the function is stopped.

In addition, since the incoming call is transmitted to the extension terminal through the private exchange period E1 signaling with the telephone station, the transmission time of the incoming call is minimized.

In addition, even when the calling terminal is an extension terminal, it is possible to provide a ring back tone service, and to provide a different ring back tone for each called party or calling party.

Claims (17)

In the call ring service providing system, A telephone station which transmits an incoming call received from a trunk line terminal to a private exchange and transmits a ring back tone to the trunk line terminal; A private exchanger connected to the telephone station and a trunk line, connected to a plurality of extension terminals, and when the incoming call is received, requesting the ring back tone from a CRBT server connected to a PRI interface, and transmitting the ring back tone to the calling terminal. ; And And a CRBT (COLORing Back Tone) server for storing a plurality of sound sources for providing the ring back tone and transmitting a sound source corresponding to the ring back tone request received from the private exchange to the calling terminal through the private exchange. System for providing ring back tone service. The private exchange of claim 1, A trunk board connected to the telephone station through the trunk line; An E1 board connected to the CRBT server through the PRI interface; A subscriber card connected with a plurality of extension terminals; A storage unit which stores a ring back tone IE according to the outgoing call number or the incoming call number of the incoming call; And a switching unit configured to set a plurality of extension terminals connected to the plurality of extension terminals and the trunk line terminal through the subscriber card, or to set up an extension communication path between the extension terminals. The method of claim 2, wherein the switching unit, And a message processing unit for transmitting a setup message including a ring back tone IE according to the outgoing call number or the incoming call number of the incoming call to the CRBT server. The method of claim 3, wherein the ring back tone IE, A system for providing a ring back tone service including at least one of an incoming call number, an outgoing call number of the incoming call, a caller group information indicating that the terminal calling the incoming call is a trunk line terminal or an extension terminal or a called party group information to which the called terminal belongs. . The method of claim 3, wherein the message processing unit, And providing the setup ring message by including the ring back tone IE in a setup message of a message flow of a PRI interface. The method of claim 5, wherein the setup message, And a Sending complete IE field, a Bearer capability IE field, a Channel identification IE field, a Calling party number IE field, a Called party number IE field, and a ring back tone IE field, wherein the call back tone IE field includes a calling party sub-IE. System for providing ring back tone service divided into fields and call party information (Called Party Sub-IE). The method of claim 6, The calling information includes a Calling Party Information Sub-IE field, a Calling Party content Length field, a Class Of Service field, a Tenant field, a Group Type field, a Group number field, and a Tel number field. The incoming information includes a Called Party Information Sub-IE field, a Called Party content Length field, a Class Of Service field, a Tenant field, a Group Type field, a Group number field, and a Tel number field. The method of claim 1, wherein the CRBT server, And receiving a setup message for requesting the ring back tone from the private exchange, and transmitting a sound source corresponding to the ring back tone IE included in the setup message to the calling terminal through the private exchange. The method of claim 1, wherein the CRBT server, A DPM board connected to the private exchange via a PRI interface and identifying a ring back tone IE included in the setup message; A database storing the plurality of sound sources; And And a control unit for searching for the sound source corresponding to the ring back tone IE identified by the DPM board in the database and transmitting the sound source to the calling terminal. The method of claim 9, wherein the control unit, If the caller group information of the ring back tone IE is a trunk line terminal, the ring back tone according to the company advertisement sound source is provided to the calling terminal, and if the extension terminal, the ring back tone service for transmitting the ring back tone according to the company announcement sound source to the calling terminal system. The method of claim 10, wherein the control unit, System for providing a ring back tone service for transmitting a ring back tone according to the announcement of each department according to the caller group information of the ring back tone IE to the calling terminal. In the method for providing a ring back tone service, Checking whether the originating terminal of the incoming call received by the private exchange is a trunk line terminal or an extension terminal; Sending, by the private exchange, a setup message including a ring back tone IE according to the originating terminal of the incoming call to a CRBT server; And transmitting, by the CRBT server, the ring back tone corresponding to the sound source corresponding to the ring back tone IE included in the received setup message to the calling terminal through the private exchange. The method of claim 12, wherein the setup message, Providing the ring back tone service to generate the setup message by including the ring back tone IE in a setup message of a message flow of a PRI interface. The method of claim 12, wherein the ring back tone IE, Providing a ring back tone service including at least one of an incoming call number, an outgoing call number of the incoming call, a caller group information indicating that the call originating terminal is a trunk line terminal or an extension terminal, or a called party group information to which the called terminal belongs. How to. The method of claim 12, wherein the transmitting of the ring back tone to the calling terminal comprises: If the caller group information of the ring back tone IE included in the setup message is the trunk line terminal, the CRBT server transmits the ring back tone according to the recall advertisement sound source to the trunk line terminal. A method for providing a ring back tone service transmitted to an extension terminal. The method of claim 13, wherein the transmitting of the call ring tone to the calling terminal comprises: Method for providing a ring back tone service for transmitting a ring back tone according to the department-specific announcement sound source corresponding to the caller group information of the ring back tone IE to the extension terminal. The method of claim 13, Connecting, by the private exchange, a call path for the incoming call while requesting a disconnection from the CRBT server when the called terminal answers the incoming call; And if the CRBT server is requested to release the connection, disconnecting the connection with the private exchange while stopping the transmission of the ring back tone.

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