JP2005318178A - Telephone exchange method and system for ip telephone terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telephone exchange method and a telephone exchange system which can reduce speech delay or deterioration in speech quality. <P>SOLUTION: The telephone exchange method between telephone terminals makes a call connection between the telephone terminals through a telephone network at a call connection request and sets a channel between the telephone terminals through the telephone network. Then while the channel is disconnected, a channel is set between the telephone terminals through an IP network and speech signals are sent and received through the channel of the IP network. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telephone exchange method and system for establishing a connection between IP telephone terminals via a private electronic exchange such as IP-PBX.

  Conventionally, when an IP telephone terminal accommodated in an IP-PBX is connected to an IP telephone terminal accommodated in another IP-PBX, there is a form in which a connection is made between two IP-PBXs using a dedicated line. Referring to FIG. 1, a call connection sequence in such a form will be described. Here, triggered by a call from the first telephone terminal 1a, a call setup procedure (SETUP) for the second telephone terminal 1b via the first PBX device 2a, the PBX relay station 4 and the second PBX device 2b, and the response The call setup acceptance procedure (CALL PROC) is executed. The call to the second telephone terminal 1b is returned to the calling side as being called (ALER), and the ringing tone (PBT transmission) is sent to the first telephone terminal 1a. A response procedure (CONN) triggered by off-hook in the second telephone terminal 1a is executed for the first telephone terminal 1a via the second PBX device 2b, the relay station 4 and the first PBX device 2a. Thereby, multiple link connection between the 1st telephone terminal 1a and the 2nd telephone terminal 1b is attained. The term “multiple link connection” as used herein means a connection form in which a plurality of communication nodes are sequentially connected such as a plurality of telephone exchanges or relay stations.

  However, in the case of such a multi-link connection, voice packetization and decompression compression are performed between the first telephone terminal 1a and the first PBX device 2a, and then voice packetization and decompression are performed between the first PBX device 2a and the second PBX device 2b. The compression, and voice packetization, decompression and compression, and voice packetization are repeatedly performed between the second PBX device 2b and the second telephone terminal 1b. Therefore, as a whole, there is a problem that a voice delay or a deterioration of voice quality occurs greatly in a call between the first telephone terminal 1a and the second telephone terminal 1b.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a telephone exchange method and system that reduce voice delay or voice quality degradation.

  The telephone exchange method according to the present invention is a telephone exchange method for exchanging between IP telephone terminals. In response to a call connection request, the IP telephone terminals are call-connected via a telephone network, and the IP telephone terminals are A first call path setting step for setting a call path via the telephone network; a second call path setting step for setting a call path via the IP network between the IP telephone terminals while cutting the call path; A voice transmission / reception step of transmitting / receiving a voice signal through a communication path via the IP network.

  A telephone switching system according to the present invention is a telephone switching system including at least two IP telephone terminals and at least two PBX apparatuses accommodating each of the IP telephone terminals, and each of the PBX apparatuses responds to a call connection request. In response, a first call path setting means for making a call connection between the IP telephone terminals via the telephone network and setting a call path via the telephone network between the IP telephone terminals, and disconnecting the call path Second communication path setting means for setting a communication path via the IP network between the IP telephone terminals, and each of the IP telephone terminals communicates between the IP telephone terminals through the communication path via the IP network. And a voice transmission / reception means for transmitting / receiving a voice signal.

  According to the telephone exchange method of the present invention, a configuration is provided in which a communication path, that is, a path is replaced with a path formed by an IP network while maintaining a call connection set through the telephone network. As a result, the telephone terminals that make the call connection are connected by one link via the IP network, so that a one-link call in which each of the voice compression and decompression processes is performed only once is achieved. Thereby, it is possible to reduce voice delay or voice quality degradation.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 2 shows an embodiment of the present invention and shows a configuration of a telephone exchange system. Here, the first telephone terminal 1a is an IP telephone terminal accommodated in the first PBX device 2a. The first telephone terminal 1b is an IP telephone terminal accommodated in the second PBX device 2b. The first PBX device 2a and the second PBX device 2b are connected to the PBX relay station 40 by a telephone network, that is, dedicated lines 30a and 30b. The first telephone terminal 1a and the first PBX device 2a are connected to the IP network 50 via the LAN 15a. The second telephone terminal 1b and the second PBX device are connected to the IP network 50 via the LAN 15b.

  Dedicated lines 30a and 30b are conventional digital telephone lines such as ISDN, and are telephone networks having a plurality of B channels for transmitting voice signals and a D channel common line for transmitting control signals such as call control signals. . The IP network 50 is an IP network that exchanges packet data by the IP protocol (Internet Protocol), and a network such as an IP-VPN is assumed. As a modification, instead of the dedicated lines 30a and 30b, a plurality of IP dedicated lines using the ISDN protocol once passing through the IP network 50 may be used. Further, in this embodiment, an example in which one telephone terminal is accommodated in one PBX apparatus is shown, but the present invention is not limited to this, and there are a plurality of PBX apparatuses accommodating a plurality of telephone terminals. The structure equipped with the stand is taken into consideration.

  FIG. 3A shows a normal processing procedure in the telephone exchange method executed in the telephone exchange system. The processing procedure shown in this figure will be described with reference to the components shown in FIG.

  The first telephone terminal 10a and the second telephone terminal 10b perform a multi-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b (step S01). Multi-link calls can be accomplished using a conventional call connection procedure as shown in FIG. Here, it is assumed that a one-link call is requested. A request for a one-link call is, for example, a form in which a one-link call is always scheduled every time a call connection occurs, triggered by the call connection request itself. Further, when the telephone terminal is a wireless terminal, it is possible to assume that a request for one link call has occurred when a handover, that is, an antenna switching between access stations occurs.

  First, the second PBX device 20b determines the possibility of 1-link connection (step S02). The second PBX device 20b that has determined that there is a possibility of one-link connection then transmits a one-link start request message to the PBX relay station 40 (step S03). In response to this, the PBX relay station 40 transmits a one-link start request message to the first PBX device 20a (step S04).

  In response to the reception of the one-link start request message, the first PBX device 20a determines the possibility of a one-link call (step S05). Next, the first PBX device 20a determines the type of compression method and captures resources (step S06). Here, the acquisition of resources means securing resources including at least securing the frequency band of the speech path. Next, the first PBX device 20a transmits a one-link reconfiguration execution message to the PBX relay station 40 (step S07). In response to this, the PBX relay station 40 transmits a one-link reconfiguration execution message to the second PBX device 20b (step S08).

  The second PBX device 20b that has received the one-link replacement execution message performs resource acquisition (step S09). Next, the second PBX device 20b transmits the result as an OK message to the PBX relay station 40 (step S11). In response to this, the PBX relay station 40 transmits an OK message to the first PBX device 20a (step S12).

  In response to the reception of the OK message, the first PBX device 20a includes, in the first telephone terminal 10a accommodated therein, a path order including the IP address of the second telephone terminal 10b that is the counterpart and information that specifies the compression method to be used. Is transmitted (step S13). On the other hand, the second PBX device 20b also transmits a path order including the IP address of the first telephone terminal 10a which is the counterpart and information specifying the compression method to be used to the second telephone terminal 10b accommodated therein (step S11). .

  As a result of the above, a one-link call is performed between the first telephone terminal 10a and the second telephone terminal 10b by specifying the other party's IP address and using the same compression method (step S14).

  FIG. 3B shows a further processing procedure at the normal time in the telephone exchange method executed in the telephone exchange system. Here, the first telephone terminal 10a and the second telephone terminal 10b perform a one-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b according to the processing procedure shown in FIG. 3A. (Step S14). This figure shows a processing procedure for returning from a one-link call to a plurality of links in such a situation.

  First, the first PBX device 20a transmits a multiple link reconfiguration execution message to the PBX relay station 40 (step S15). Next, the first PBX device 20a transmits a path order indicating the return of multiple links to the telephone terminal 10a (step S16), and releases resources captured for the one-link call via the IP network (step S17).

  On the other hand, the PBX relay station 40 that has received the multiple link replacement execution message from the first PBX device 20a transmits the multiple link replacement execution message to the second PBX device 20b (step S18). In response to this, the second PBX device 20b similarly transmits a path order indicating the return of multiple links to the telephone terminal 10b (step S19), and releases the resources captured for the one-link call via the IP network (step S19). S20). As a result, the first telephone terminal 10a and the second telephone terminal 10b return from the one-link call to the multiple-link call (step S21).

  FIG. 4 illustrates the configuration of control messages exchanged between the first PBX device and the second PBX device shown in FIG. The configuration of the control message exchanged between the first PBX device and the second PBX device and the exchange procedure constitute one protocol, and it is possible to switch the path from the multi-link call which is a basic call call to the one-link call. Protocol. Control messages for such protocols shall be exchanged over the D-channel common line and shall include a facility (FAC) signal as defined in “Examples of how to use manufacturer specific information” in Appendix F of JS-11582. It can consist of formulating as manufacturer specific information.

  In this embodiment, the control message includes an operation message 61, an OK message 62, and an NG message 63. The operation message 61 includes an identifier 62 indicating that the operation message is an operation message, an operation 63, and an argument 64. The operation 63 includes an operation value, which takes, for example, values of 0x0001 to 0x0003. “0x0001” indicates a “1 link start request message”, “0x0002” indicates a “1 link replacement execution message”, and “0x0003” indicates a “multiple link replacement execution message”. It is shown that.

  The argument 64 includes a telephone terminal type, an IP address, a voice port number, a FAX port number, compression type information, and PAD information. The compression type information includes information designating a priority compression type, a priority transmission cycle, and a possible compression type when a 1 link start request is made (that is, when the operation value is 0x0001). Further, the compression type information includes the determined compression type and the determined transmission cycle when the re-execution is performed (that is, when the operation value is 0x0002).

  The OK message 65 includes an identifier 66 indicating that the message is an OK message. The OK message 65 is a message meaning OK in the message transmission itself, that is, an acknowledgment response. The NG message 67 is composed of an identifier 68 indicating an NG message notifying the occurrence of an error and an error number 69. The error number 69 takes a value of 1000 to 1004, for example. “1001” indicates that the service is not allowed due to restriction by the system flag or being an existing terminal, “1002” indicates that resource acquisition is unsuccessful because bandwidth acquisition of the communication path is impossible, and “1003” indicates , Indicating that the negotiation at the time of arbitrating the compression method is unsuccessful, “1004” indicates that the failure is due to a temporary failure such as a state mismatch that may be succeeded by retry, and “1000”. Indicates other problems.

  FIG. 5 shows a processing procedure for determining a compression method in the processing procedure shown in FIG. 3A. This figure shows a voice packet compression method determination process performed mainly by the cooperation station (PBX 20a) in response to a one-link start request from the request station side (PBX 20b). As a compression method to be determined, for example, ITU recommendation standard G.I. 711, G.G. 729a, G.A. 723.1, G.M. 723.1 (6.3K) and G.M. 723.1 (5.3K).

  First, the cooperation station (PBX 20a) receives a one-link start request designating the priority compression method and selectable compression method of the telephone terminal accommodated by the requesting station side (PBX device 20b) (step S71). Next, it is determined whether or not the priority compression method of the requesting station side telephone terminal matches the priority compression method of the local station side telephone terminal (step S72). If they match, the matching priority compression method is determined as the used compression method (step S73). On the other hand, if they do not match, it is provisionally determined that the priority compression method of the telephone terminal having a higher priority is used according to the station data (step S74).

  Next, the cooperation station (PBX 20a) determines whether or not the temporarily determined priority compression method is a selectable compression method for both telephone terminals (step S75). If the compression method is selectable by both telephone terminals, the temporarily determined priority compression method is determined as the compression method to be used (step S79). On the other hand, if it is not the selectable compression method of both telephone terminals, it is provisionally determined that the priority compression method of the other telephone terminal is used (step S76). Next, it is determined again whether or not the preferentially determined priority compression method is a selectable compression method for both telephone terminals (step S77). If the compression method is selectable by both telephone terminals, the temporarily determined priority compression method is determined as the compression method to be used (step S79). On the other hand, if both of the telephone terminals are not selectable compression methods, the one-link call is abandoned and the process is stopped (step S78).

  As a result of the above processing procedure, the cooperation station (PBX 20a) responds with the determined compression method to the requesting station (PBX 20b), whereby the telephone terminal 10a accommodated in the cooperation station PBX 20a and the telephone terminal 10b accommodated in the requesting station PBX 20b. A one-link call is performed using the compression method determined as follows. On the other hand, when abandoning the one-link call and canceling the process, the cooperation station (PBX 20a) responds with an NG message to the requesting station (PBX 20b), thereby giving up the one-link call as a whole system. The link call will continue.

  FIG. 6A is a modified example of the telephone exchange method executed in the telephone exchange system, and shows a processing procedure at the time of abnormality. This figure shows a processing procedure when the second PBX device 20b, that is, the one link requesting station side, times out waiting for a response to the one link start request message. The processing procedure shown in this figure will be described with reference to the components shown in FIG.

  The first telephone terminal 10a and the second telephone terminal 10b perform a multi-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b (step S31). Multi-link calls can be accomplished using a conventional call connection procedure as shown in FIG.

  First, the second PBX device 20b determines the possibility of one link connection and starts one timer T1 (step S32). The set time of the timer T1 is 3 seconds, for example. The second PBX device 20b that has determined that there is a possibility of one-link connection then transmits a link start request message to the PBX relay station 40 (step S33). In response to this, the PBX relay station 40 transmits a one-link start request message to the first PBX device 20a (step S34).

  In response to receiving the one-link start request message, the first PBX device 20a determines the possibility of a one-link call (step S35). Next, the first PBX device 20a determines the type of compression method and captures resources (step S36). Further, the first PBX device 20a starts a timer T2 (step S36 '). The set time of the timer T2 is 4 seconds, for example. Next, the first PBX device 20a transmits a one-link reconfiguration execution message to the PBX relay station 40 (step S37). In response to this, the PBX relay station 40 transmits a one-link reconfiguration execution message to the second PBX device 20b (step S38). It is assumed that the one-link reconfiguration execution message arrives at the second PBX device 20b with some delay due to processing delay or transmission delay.

  On the other hand, the second PBX device 20b that has started the timer in step S32 determines that there is no response from the first PBX device 20b within the timer set time in response to the arrival of the timer set time, and cancels the one-link process. (Step S39). Next, the second PBX device 20b transmits a multiple link reconfiguration execution message to the PBX relay station 40 (step S40). In response to this, the PBX relay station 40 transmits a multiple link switching execution message to the first PBX device 20a (step S41). The second PBX device 20b that has received the one-link reconfiguration execution message from the first PBX device 20a with a delay will discard this message.

  As a result, the one-link call is stopped between the first telephone terminal 10a and the second telephone terminal 10b, and the previous multi-link call is continued.

  FIG. 6B is a modified example of the telephone exchange method executed in the telephone exchange system, and shows a further processing procedure at the time of abnormality. This figure shows a processing procedure when the first PBX device 20a, that is, the one link cooperation station side, times out waiting for a response to the one link replacement execution message. The processing procedure shown in this figure will be described with reference to the components shown in FIG.

  As a premise, the first telephone terminal 10a and the second telephone terminal 10b perform a multi-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b. From this state, the second PBX device 20b transmits a link start request message to the PBX relay station 40, and in response, the PBX relay station 40 transmits a one link start request message to the first PBX device 20a. The first PBX device 20a determines the possibility of a one-link call (see steps S31 to S35 in FIG. 6A).

  At this point, as shown in FIG. 6B, the first PBX device 20a determines the type of compression method and captures resources (step S36). Further, the first PBX device 20a starts a timer T2 (step S36 '). The set time of the timer T2 is 4 seconds, for example. Next, the first PBX device 20a transmits a one-link reconfiguration execution message to the PBX relay station 40 (step S37). In response to this, the PBX relay station 40 transmits a one-link reconfiguration execution message to the second PBX device 20b (step S38).

  The second PBX device 20b that has received the one-link replacement execution message acquires resources (step S39), and transmits a path order to the effect of switching the path to a one-link call to the second telephone terminal 10b (step S39). S40). At this time, the second telephone terminal 10b and the second PBX device 20b operate on the premise of a one-link call, but the first telephone terminal 10a recognizes a silent state. Next, the second PBX device 20b transmits an OK message to the PBX relay station 40 (step S41). In response to this, the PBX relay station 40 transmits an OK message to the first PBX device 20a (step S42). It is assumed that the OK message arrives at the second PBX device 20a with some delay due to processing delay or transmission delay.

  On the other hand, the first PBX device 20a that has started the timer in step S36 ′ determines that there is no response from the second PBX device 20a within the timer set time in response to the arrival of the timer set time, and performs one-link processing. Cancel and release the resources captured for the one-link call (step S43). Next, the first PBX device 20a transmits a multiple link reconfiguration execution message to the PBX relay station 40 (step S44). In response to this, the PBX relay station 40 transmits a multiple link switching execution message to the second PBX device 20b (step S45). The first PBX device 20a that has received the OK message from the second PBX device 20b with a delay discards the message.

  The second PBX device 20b that has received the multi-link switching execution message releases the resources captured for the one-link call (step S47), and notifies the second telephone terminal 10b that the path is switched to the multi-link call. The path order is transmitted (step S46). As a result, the one-link call is stopped between the first telephone terminal 10a and the second telephone terminal 10b, and the previous multi-link call is continued.

  FIG. 7A is a modified example of the telephone exchange method executed in the telephone exchange system, and shows a further processing procedure at the time of abnormality. This figure shows a processing procedure when resource acquisition is unsuccessful on the first PBX device 20a, that is, the one-link cooperation station side. The processing procedure shown in this figure will be described with reference to the components shown in FIG.

  The first telephone terminal 10a and the second telephone terminal 10b perform a multi-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b (step S51). Multi-link calls can be accomplished using a conventional call connection procedure as shown in FIG.

  First, the second PBX device 20b determines the possibility of 1-link connection (step S52). The second PBX device 20b that has determined that there is a possibility of one-link connection then transmits a one-link start request message to the PBX relay station 40 (step S53). In response to this, the PBX relay station 40 transmits a one-link start request message to the first PBX device 20a (step S54).

  In response to receiving the one-link start request message, the first PBX device 20a determines the possibility of a one-link call (step S55). Here, if the determination of the compression method type is unsuccessful or the resource acquisition is unsuccessful, the first PBX device 20a transmits an NG message to the PBX relay station 40 (step S56). In response to this, the PBX relay station 40 transmits an NG message to the second PBX device 20b (step S57). The second PBX device 20b that has received the NG message gives up and stops the one-link call (step S58). As a result, the multi-link call is continuously performed between the first telephone terminal 10a and the second telephone terminal 10b.

  FIG. 7B is a modification of the telephone exchange method executed in the telephone exchange system, and shows a further processing procedure at the time of abnormality. This figure shows a processing procedure when resource acquisition is unsuccessful on the second PBX device 20a, that is, the one-link request station side. The processing procedure shown in this figure will be described with reference to the components shown in FIG.

  The first telephone terminal 10a and the second telephone terminal 10b perform a multi-link call through the first PBX device 20a, the PBX relay station 40, and the second PBX device 20b (step S51). Multi-link calls can be accomplished using a conventional call connection procedure as shown in FIG.

  First, the second PBX device 20b determines the possibility of 1-link connection (step 52). The second PBX device 20b that has determined that there is a possibility of one-link connection then transmits a one-link start request message to the PBX relay station 40 (step S53). In response to this, the PBX relay station 40 transmits a one-link start request message to the first PBX device 20a (step S54).

  In response to receiving the one-link start request message, the first PBX device 20a determines the possibility of a one-link call (step S55). Next, the first PBX device 20a determines the type of compression method and captures resources (step S56). Next, the first PBX device 20a transmits a one-link reconfiguration execution message to the PBX relay station 40 (step S57). In response to this, the PBX relay station 40 transmits a one-link switching execution message to the second PBX device 20b (step S58).

  The second PBX device 20b that has received the one-link replacement execution message acquires resources for a one-link call (step S59). Here, it is assumed that the second PBX device 20b has failed in resource acquisition. In this case, the second PBX device 20b transmits an NG message to the PBX relay station 40 (step S60). In response to this, the PBX relay station 40 transmits an NG message to the first PBX device 20a (step S61). In response to the reception of the NG message, the first PBX device 20a releases the resources acquired for the one-link call (step S62). As a result, the multi-link call is continuously performed between the first telephone terminal 10a and the second telephone terminal 10b.

  In the above embodiment, unlike the conventional connection method, voice packetization, compression, and decompression are repeated many times, and voice packetization, compression, and decompression need only be performed once. Therefore, audio delay is reduced and audio quality is improved. Further, in the conventional connection method, the station equipment such as PBX always processes both the call signal and the control signal, so the resource restriction such as the frequency band is large. However, according to the present invention, the telephone terminal Since voice packets are directly transmitted and received between each other, the number of voice packets in the station is reduced and the bandwidth can be used effectively.

  The telephone exchange method and system according to the present invention can be applied to a form in which IP-PBX and IP-PBX are connected via a LAN. Further, the present invention can be realized by implementing a transition protocol to one link connection in software used in the conventional IP-PBX. In addition, when the opposite station does not implement the migration protocol to 1-link connection, it is possible to communicate with the conventional connection, and a highly flexible operation mode can be realized.

It is a sequence diagram which shows the conventional telephone exchange method. It is an Example of this invention and is a block diagram which shows the structure of a telephone switching system. It is a flowchart which shows the process sequence at the time of the normal in the telephone exchange method performed in a telephone exchange system. It is a flowchart which shows the further process sequence at the time of the normal in the telephone exchange method performed in a telephone exchange system. It is explanatory drawing explaining the structure of the control message exchanged between the 1st PBX apparatus and 2nd PBX apparatus which are shown by FIG. It is a flowchart which shows the process sequence which determines the compression system in the process sequence shown by FIG. 3A. It is the modification in the telephone exchange method performed in a telephone exchange system, and is a sequence diagram which shows the process sequence at the time of abnormality. It is a modification in the telephone exchange method performed in a telephone exchange system, and is a sequence diagram which shows the further process sequence at the time of abnormality. It is a modification in the telephone exchange method performed in a telephone exchange system, and is a sequence diagram which shows the further process sequence at the time of abnormality. It is a modification in the telephone exchange method performed in a telephone exchange system, and is a sequence diagram which shows the further process sequence at the time of abnormality.

Explanation of symbols

10a First telephone terminal 10b Second telephone terminal 15a, 15b LAN
20a 1st PBX device 20b 2nd PBX device 30a, 30b Dedicated line 40 PBX relay station 50 IP network

Claims (12)

A telephone exchange method for connecting between IP telephone terminals,
In response to a call connection request, a first call path setting step of establishing a call path between the IP telephone terminals via the telephone network and setting a call path between the IP telephone terminals via the telephone network;
A second call path setting step for setting a call path via an IP network between the IP telephone terminals while cutting the call path;
A voice transmission / reception step of transmitting / receiving a voice signal through a communication path via the IP network;
The telephone exchange method characterized by including. The second speech path setting step includes: an IP address setting step for setting a destination of each IP telephone terminal using an IP address assigned to each of the IP telephone terminals; An audio compression method setting step for setting the same audio signal compression method,
The voice transmission / reception step includes a step of transmitting a voice packet compressed by the voice compression method toward the destination IP address in each of the IP telephone terminals, and a decompression from the destination IP address by the voice compression method. Receiving the voice packet that can be received. The method of claim 1, further comprising the step of:   2. The telephone exchange method according to claim 1, wherein the second call path setting step is a step in response to a call path setting request via an IP network.   4. The telephone exchange method according to claim 3, wherein the call path setting request via the IP network is a request triggered by establishment or handover of a call connection between the IP telephone terminals.   3. The telephone exchange method according to claim 2, wherein the voice compression method setting step is a step of setting one of the voice compression methods that can be used together in each of the IP telephone terminals.   The voice compression scheme setting step is a step of setting a voice compression scheme specified by any one of the IP telephone terminals from among voice compression schemes that can be used together in each of the IP telephone terminals. The telephone exchange method according to claim 5.   The second communication path setting step includes a step of exchanging a message for setting a communication path in the IP network between a plurality of PBXs accommodating each of the IP telephone terminals, and the arrival of the message for a predetermined time. 2. The telephone according to claim 1, further comprising: a step of monitoring the communication path; and a step of canceling the setting of a speech path through the IP network if the message does not arrive within the predetermined time. method of exchange.   The second speech path setting step includes a resource capturing step including at least securing a frequency band necessary for setting a speech path in the IP network in each of a plurality of PBXs accommodating each of the IP telephone terminals, 2. The telephone exchange method according to claim 1, further comprising the step of canceling the setting of a communication path via the IP network when the resource acquisition is poor.   2. The telephone exchange method according to claim 1, further comprising the step of disconnecting the communication path via the IP network and re-setting the communication path via the telephone network between the IP telephone terminals. A telephone switching system including at least two IP telephone terminals and at least two PBX devices accommodating each of the IP telephone terminals,
Each of the PBX devices makes a call connection between the IP telephone terminals via a telephone network in response to a call connection request, and sets a communication path via the telephone network between the IP telephone terminals. Setting means; and second call path setting means for setting a call path via an IP network between the IP telephone terminals while cutting the call path,
Each of the IP telephone terminals includes voice transmission / reception means for transmitting / receiving a voice signal between the IP telephone terminals through a communication path via the IP network.   11. The telephone exchange system according to claim 10, wherein the first speech path setting means sets the speech path via a D channel of the telephone network.   11. The telephone exchange system according to claim 10, wherein the second speech path setting means sets the speech path by exchanging FAC messages via the D channel of the telephone network.

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