JP2005354641A - Callback system, method, program, and recording medium of ip telephone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a callback system, a method, a program and a recording medium of an IP telephone capable of performing callback processing directed by a relay server when an outgoing side terminal is disconnected, securing the line (session) resource of the IP telephone at a relay server side, and protecting the telephone call from being cut down by the outgoing side by switching into a "telephone line reservation function" or a "re-calling function" which is required for an urgent message. <P>SOLUTION: The callback system is provided with a line retention means (1) for retaining a connecting line of a public line network 5 without transmitting a disconnection signal sent by outgoing side 1 when a number received at a receiver 3 is a predetermined telephone number, and a callback means (1) for sending back a callback signal to the outgoing side based on the disconnect signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a call back system and method, a program, and a recording medium in an IP telephone for performing a call back from a receiver side to a caller side in an emergency telephone connection using an IP telephone.

  As a technology that has been put into practical use with respect to conventional telephone calls, telephone lines based on a subscriber telephone network that perform telephone calls via a line network constituted by physical communication lines are widely used. In recent years, with the development of the Internet, an IP (Internet Protocol) telephone system has been put into practical use as a telephone call technology using an IP (Internet Protocol) network. Calls in the IP telephone system are not established through physical connections such as lines as in existing subscriber telephone networks, but are established through virtual connections called logical sessions on the IP network. Yes.

  Descriptions of technical standards and the like for such IP telephone systems are published as documents by the IETF (Internet Engineering Task Force), a consortium established to promote the standardization of various new technologies developed on the Internet. ing. As this document, RFC3261 (RFC2543), RFC3398, etc., which are known as RFC (Requests for Comment), are known.

  Furthermore, in the case of emergency calls on the conventional subscriber telephone network, even if the call is disconnected from the caller side, the connection is secured by calling back from the emergency call reception desk to the caller side even if the caller is disconnected. It is a system. This emergency call function is extremely important socially, and not only the emergency call system on the subscriber telephone network but also the IP phone system needs to be improved. ing.

  Here, the configuration of the conventional subscriber telephone network and the IP telephone system are compared. First, as shown in FIG. 4, the existing subscriber telephone network includes subscriber telephone terminals 100 and 101, subscriber exchanges 103 and 104, and a relay exchange 102. Here, as shown in FIG. 5, a call connected to the reception desk 109 for handling an emergency call is made from the subscriber telephone terminal 105 to the subscriber exchange 106, the relay exchange 107, and the subscriber exchange 108 that accommodates the reception desk 109. And connected to the reception board 109. When the emergency call is connected, the “line reservation function” that maintains the line up to the reception stand 109 even if the telephone call at the subscriber telephone terminal 105 is cut off, or the emergency call reporter who cuts off the call at the subscriber telephone terminal 105 side. "Recall function" that can call up again is prepared.

  Among these, in the “line reservation function”, the telephone line is connected to the subscriber exchange 108 and the relay exchange 107 even if the call is an emergency call, even if the disconnection signal is received from the subscriber telephone terminal 105 on the calling side. This is a function that reserves a telephone line without opening it and only opens the telephone line by a disconnection signal from the reception stand 109 side.

A function that allows the subscriber telephone terminal 105 that has disconnected the call to be called by instructing the subscriber exchange 105 to recall the telephone line that has been reserved without being released is called “ "Recall function". At this time, since the telephone line is reserved by the “line reservation function”, it has a configuration in which a reliable “recall” can be performed by pressing a recall start button (not shown) provided on the reception stand 109 side (non-patent References 1 and 2).
Functions provided in the existing fixed network: http: // www. zdnet. co. jp / roadband / 0304/15 / lp11. html Study Group (Ministry of Internal Affairs and Communications) Report on Important Communications in the Telecommunications Business Chapter 6 (3) Ensuring emergency calls on IP phones http: // www. soumu. go. jp / s-news / 2003/030411 html

  However, the emergency call line connection in the conventional IP telephone system exists only as a logical resource called a session on the IP network, and the session resource is established and released by the IP telephone terminal. In the server system of the telephone system, the line / session resource management cannot be performed directly, and only an instruction is sent to the IP telephone terminal. Therefore, it has been difficult to provide various functions such as a “line reservation function” and a “recall function” for emergency calls in the existing subscriber telephone network.

  In view of such a problem, the present invention enables call back processing by an instruction from a relay server at the time of disconnection from a caller terminal, and can secure a line (session) resource of an IP telephone terminal on the relay server side. An object of the present invention is to provide an IP telephone call back system and method, program, and recording medium that can prevent a caller from disconnecting as a "line reservation function" or "recall function" necessary for reporting. It is said.

  According to the first aspect of the present invention, when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the calling side of the IP telephone network, the public telephone line network is provided. A call back system in an IP phone for calling back from the connected IP phone signal conversion server side, wherein the caller sends a disconnection signal sent by the caller when the callee number is a preset phone number Line holding means for holding the connection line of the public line network without transmitting to the called side, and call back means for sending back a call back signal to the calling side based on the disconnection signal.

  According to a second aspect of the present invention, in the first aspect, the call-back means sends back the call-back signal and sends a notification sound for notifying the callee that the call is being returned.

  According to a third aspect of the present invention, in the second aspect, the notification sound is at least one of a voice announcement and a chime sound.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the call-back means selects a preset telephone number based on the telephone number at the time of transmission together with the call-back signal. And send it to the callee as the caller's phone number.

  According to a fifth aspect of the present invention, when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected on the outgoing side of the IP telephone network, the public telephone line is provided. A call back method in an IP phone for calling back from the IP phone signal conversion server connected to a network, wherein the caller sends a disconnect signal when the called number is a preset phone number Holding the connection line by means of line holding means for holding the connection line of the public line network without transmitting to the called side, and for returning a call back signal to the calling side based on the disconnection signal And a step of sending back the call back signal by the call back means.

  According to a sixth aspect of the present invention, in the fifth aspect, the call-back means sends back a call-back signal and sends a notification sound for notifying the callee that the call is being returned.

  According to a seventh aspect of the present invention, in the sixth aspect, the notification sound is at least one of a voice announcement and a chime sound.

  The invention according to claim 8 is the invention according to any one of claims 5 to 7, wherein the call-back means selects a telephone number set in advance based on the call-back telephone number together with the call-back signal. And send it to the callee as the caller's phone number.

  According to a ninth aspect of the present invention, when a call made from an IP telephone network to a public telephone line network via an IP telephone signal conversion server is disconnected on the outgoing side of the IP telephone network, the public telephone line is provided. A call back program in an IP phone for calling back from the IP phone signal conversion server connected to the network, and the disconnect signal sent by the caller when the callee number is a preset phone number Holding the connection line by means of line holding means for holding the connection line of the public line network without transmitting to the called side, and for returning a call back signal to the calling side based on the disconnection signal And a step of returning the call back signal by the call back means.

  According to a tenth aspect of the present invention, in the ninth aspect, the call-back means sends back the call-back signal and sends a notification sound for notifying the callee that the call is being returned.

  In addition, according to an eleventh aspect of the present invention, in the tenth aspect, the notification sound is at least one of a voice announcement and a chime sound.

  According to a twelfth aspect of the present invention, in any one of the ninth to eleventh aspects, the call-back means selects a preset telephone number based on the call-back telephone number together with the call-back signal. And send it to the callee as the caller's phone number.

  The invention according to claim 13 can be executed by being installed in a server arranged on the IP network according to any one of claims 9 to 12.

  Further, the present invention as set forth in claim 14 is directed to the public telephone line when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the calling side of the IP telephone network. A recording medium for recording a call back program in an IP telephone for calling back from the IP telephone signal conversion server connected to the network, wherein the call origination number is a telephone number set in advance. Holding the connection line by means of line holding means for holding the connection line of the public line network without transmitting the disconnection signal transmitted by the side to the called side, and calling to the calling side based on the disconnection signal Recording a call back program in an IP phone, comprising: returning the call back signal by a call back means for sending back a return signal.

  According to a fifteenth aspect of the present invention, in the fourteenth aspect, the call-back means sends back the call-back signal and sends a notification sound for notifying the callee that the call is being returned. A call back program in an IP phone is recorded.

  According to a sixteenth aspect of the present invention, in the fifteenth aspect, the notification sound is at least one of a voice announcement and a chime sound. To do.

  According to a seventeenth aspect of the present invention, in any one of the fourteenth to sixteenth aspects, the call-back means selects a preset telephone number based on the call-back telephone number together with the call-back signal. A call back program in an IP telephone is recorded, which is transmitted to a call back destination as a caller telephone number.

  The present invention according to claim 18 is the program for calling back an IP telephone according to any one of claims 14 to 17, wherein the program is installed and executable on a server arranged on the IP network. Record.

  According to the present invention, it is possible to perform a call back process based on an instruction from the relay server when disconnecting from the originating terminal, and the line (session) resource of the IP telephone terminal can be secured on the relay server side. It is possible to provide a call back system and method, a program, and a recording medium in an IP phone that can prevent a call from being disconnected from a caller as a “line reservation function” or “recall function”.

  FIG. 1 is a block diagram for explaining an IP telephone system according to an embodiment of a call back system and method, program, and recording medium in an IP telephone. In the embodiment of the automatic recall system in the IP telephone system of the present invention, the PSTN-GW (PSTN-GW) connecting the IP network 4 to which the IP telephone terminal (calling side) 2 is connected and the existing public telephone network (PSTN) 5 is connected. A connection device 1 is connected to an IP telephone terminal (transmitting side) 2 via an IP network 4 and a public telephone terminal (receiving side) 3 via an existing public telephone network (PSTN) 5. The PSTN-GW (connection device) 1 mediates call connection processing with the IP telephone terminal (calling side) 2 and the existing public telephone (calling side) 3.

  Next, FIG. 2 shows a sequence chart for explaining a call back control sequence by the IP telephone system according to the embodiment of the call back system and method, program and recording medium of the IP telephone of the present invention. Yes. The overall operation of the present embodiment will be described in detail with reference to this sequence chart.

  First, the IP telephone terminal 2 transmits a “call” signal to the PSTN-GW 1 in order to make a call (step 1: S1).

  Next, the PSTN-GW 1 compares the destination telephone number included in the “outgoing” signal with an automatic call target telephone number stored in a recording device (not shown) in the PSTN-GW 1, and performs an automatic call target. After determining that the call is to the telephone number and recording in the call management storage device (not shown) that this call is in the automatic call back instruction state, an “call” signal is sent to the existing public telephone 3. Work (Step 2: S2).

  The existing public telephone 3 that has received the “outgoing” signal returns a response signal to the IP telephone terminal 2 via the PSTN-GW 1 (step 3: S3), and the IP telephone terminal 2 and the existing public telephone 3 make a call. It is ready to be executed (step 4: S4).

  In a state where a call is in progress, a “disconnect” signal is transmitted to the PSTN-GW 1 in order to disconnect from the IP telephone terminal 2 (step 5: S5).

  At this time, the PSTN-GW 1 notifies the existing public telephone 3 that the call is being returned by playing a recalling sound without disconnecting the existing public telephone 3 (step 6: S6).

  The PSTN-GW 1 that has received the “disconnect” signal from the IP telephone terminal 2 determines from the information in the call management storage device that the corresponding call is in the automatic call instruction state, and does not interwork the “disconnect” signal. Then, a new call (call back) is immediately made to the IP telephone terminal 2 (step 7: S7).

  The PSTN-GW 1 that has received the “response” signal from the IP telephone terminal 2 (step 8: S8) stops the recalling sound so that a call can be made between the IP telephone terminal 2 and the existing public telephone 3. Then, the IP telephone terminal 2 and the existing public telephone 3 are connected.

  When ending the call, the existing public telephone 3 transmits a “disconnect” signal to the PSTN-GW 1 (step 9: S9).

  Upon receiving the “disconnect” signal from the existing public telephone 3, the PSTN-GW 1 cancels the automatic call back instruction state, opens the existing public telephone 3, and interworkes the “disconnect” signal with the IP telephone terminal 2.

  Upon receiving the “disconnect” signal, the IP telephone terminal 2 releases the call and terminates (step 10: S10).

  Next, referring to FIG. 3, the automatic call of the present invention is used as an alternative to the line reservation / recall function provided in the existing public telephone network when an emergency call (eg, police 110, fire department 119) is made from an IP phone. A system that uses the return function to perform a recall in response to a disconnection from the caller will be described in detail.

  FIG. 3 shows a sequence chart for explaining a call back control sequence by the IP telephone system according to the embodiment of the call back system and method, program and recording medium in the IP telephone of the present invention. As shown in FIG. 3, a telephone terminal 2 and an IP telephone adapter (VoIP-TA) 6 that terminates a SIP signal that is a call processing signal of the IP telephone system are connected by a telephone cable, and further an IP telephone adapter (VoIP-TA). 6 is connected to an IP network, logically connected to an IP telephone signal conversion server (PSTN-GW: synonymous with connection device) 1 by a SIP signal, and voice information is converted into an RTP signal according to the SIP signal procedure. Connection to an IP telephone media converter (PSTN-MGW) is possible.

  The IP telephone signal conversion server 1 internally interworkes SIP signals and ISUP signals, and is connected to a gateway exchange (IGS) in an existing subscriber telephone network via an SS7 network. The IP telephone signal conversion server 1 also controls the IP telephone media converter (PSTN-MGW) via the IP network.

  The gateway exchange (IGS) is connected to the subscriber exchange through the existing telephone network.

  In the existing subscriber telephone network, it is clear that there are several relay exchanges between the gateway exchange (IGS) and the subscriber exchange (LS). In the sequence, the relay exchange only performs the relay, and the description is omitted.

  The IP telephone media converter (PSTN-MGW) is connected to the gateway exchange (IGS) through a line for transmitting voice. The subscriber exchange (LS) is connected to a reception desk that accepts emergency calls.

  The telephone terminal 2 lifts the handset (off-hook) and dials the emergency call number (110, 119, etc.). The IP telephone adapter (VoIP-TA) 6 makes an outgoing call (INVITE) to the IP telephone signal conversion server 1 in accordance with the instruction from the telephone terminal 2 (step 20: S20).

  The IP telephone signal conversion server 1 determines that the call is an emergency call from the destination number of the received INVITE signal (the police 110, the fire fighting 119, etc.), and sets an identification flag that is an emergency call for the corresponding call.

  The IP telephone signal conversion server 1 transmits a transmission signal to the gateway switch (IGS) of the existing subscriber telephone network.

  The outgoing signal transmits the outgoing signal received by the gateway exchange (IGS) through the existing training telephone network to the subscriber exchange (LS) to which the emergency call reception desk is connected, and the subscriber exchange (LS) is sent to the reception desk. On the other hand, a transmission signal is transmitted and the reception board is called (step 21: S21).

  The reception desk responds to the call and transmits a response signal to the subscriber exchange (LS). The subscriber exchange (LS) relays the existing public telephone 3 network and transmits the response signal to the gateway exchange (IGS). The gateway exchange (IGS) relays the response signal to the IP telephone signal conversion server 1 (step 22: S22).

  Upon receiving the response signal, the IP telephone signal conversion server 1 transmits a response (200 OK) signal to the IP telephone adapter (VoIP-TA) 6 (step 23: S23).

  As described above, the telephone terminal 2 establishes a call session which is a call resource, and makes an emergency call with the reception desk.

  Next, when the telephone terminal 2 is disconnected (the handset is placed: on-hook), the IP telephone adapter (VoIP-TA) 6 transmits a disconnection (BYE) signal to the IP telephone signal conversion server 1 (steps S24: S24). ).

  At this time, the IP telephone adapter (VoIP-TA) 6 releases the call session as a call resource.

  In the IP telephone signal relay server 1, it is identified from the received disconnection (BYE) signal that the call with the identification flag being an emergency call is disconnected, and the disconnection signal is received as it is. Without interworking, it is reserved that the connection in step 2 connected to the gateway exchange (IGS) side is not disconnected, and support for sending a recall notification sound to the IP telephone media converter (PSTN-MGW) And a recall notification sound is provided to the reception (step 25: S25).

  Subsequently, the IP telephone signal conversion server 1 sends an outgoing (INVITE) signal to call the IP telephone adapter (VoIP-TA) 6 (step 26: S26). The outgoing (INVITE) signal at this time is selected and determined from a preset number based on the telephone number at the time of outgoing call received in step 20: S20 as the caller telephone number.

  The IP telephone adapter (VoIP-TA) 6 that has received the outgoing (INVITE) signal places the telephone terminal 2 in a ringing state and notifies the user.

  When the telephone terminal 2 responds to the call back (raises the handset; goes off-hook), the IP telephone adapter (VoIP-TA) 6 transmits a response (200 OK) signal to the IP telephone signal conversion server 1 (step 27: S27).

  Upon receiving the response (200 OK) signal, the IP telephone signal conversion server 1 transmits a call path reconnection instruction to the IP telephone media converter (PSTN-MGW) to re-establish a call between the telephone terminal 2 and the reception board. .

  Thereafter, when disconnection from the reception desk is performed, a disconnection signal is sent from the existing subscriber telephone network to the IP telephone signal conversion server 1 (step 28: S28). A disconnect (BYE) signal is transmitted to the telephone adapter (VoIP-TA) 6 (step 29: S29), and a line release instruction is sent to the IP telephone media converter (PSTN-MGW).

  The IP telephone adapter (VoIP-TA) 6 that has received the disconnection (BYE) signal in step 10 transmits the end-of-call state to the telephone terminal 2 (sends a BT sound, etc.), and responds to the BYE (200 OK) signal. To return to the initial state.

  As described above, when an emergency call is made from a terminal on the IP telephone system side in a system in which the IP telephone system and an existing public telephone network are connected using the present invention, the telephone terminal 2 side is disconnected. In such a case, a system that can be called back immediately and automatically can be constructed, and it is expected to be applied as a substitute for line reservation and recall that is performed by an emergency call on an existing subscriber telephone network.

  According to the embodiment of the present invention described above, in an IP telephone system connected to an existing public telephone network (PSTN), a specific destination (the existing public telephone 3 of the existing public telephone 3) whose incoming call number is set in advance at the time of outgoing call. Telephone number 2), even if the telephone terminal 2 (calling side) disconnects the call in progress, the telephone terminal 2 (in the connection device between the IP telephone call control signal and the existing public telephone network) The telephone terminal 2 (calling side) is triggered by the disconnection signal while the connection line of the existing public telephone 3 is held without transmitting the cutting signal transmitted from the calling side) to the existing public telephone network side (calling side). By immediately sending back the call signal to the telephone terminal 2, it is possible to provide an automatic call back function that is called back immediately when the telephone terminal 2 (calling side) performs a disconnection operation.

  At this time, in the connection device with the existing public telephone network, the existing call is held as it is, and it is notified by a voice announcement or the like that the call is being returned. After that, when the telephone terminal 2 (calling side) called back responds, the voice announcement is stopped, and the connection with the existing call is performed.

In other words, according to the embodiment of the present invention, it is possible to realize a function of determining whether a call is a call target (Call) based on a destination number (by comparing with information stored in a connection device such as PSTN-GW1). ,
In addition, the connection device with the existing network detects disconnection from the calling side (IP phone side), sends a special sound to the existing public telephone 3, and calls back to the calling side (IP phone side). A function that keeps playing the sound source until there is a response or until it is disconnected from the existing network side can be realized,
Further, when calling back, the caller number of the call back to the caller (IP phone side) is set from the above-mentioned callee number according to the rules set in advance in the connection device etc. (to 110) In the case of an incoming call, a function that can be shown as an outgoing call from 110) can be realized.

FIG. 1 shows a configuration diagram for explaining an IP telephone system according to embodiments of a call back system and method, program, and recording medium for an IP telephone according to the present invention. 3 shows a sequence chart for explaining a control sequence of call back by the IP telephone system according to the embodiment of the call back system and method, program, and recording medium of the IP telephone of the present invention. 3 shows a sequence chart for explaining a control sequence of call back by the IP telephone system according to the embodiment of the call back system and method, program, and recording medium of the IP telephone of the present invention. The block diagram for demonstrating the existing subscriber telephone network by a prior art is shown. The explanatory view for explaining the emergency call in the subscriber telephone network by the prior art is shown.

Explanation of symbols

1 PSTN-GW (connection equipment)
2 IP phone terminal (calling side)
3 Existing public telephone (incoming side)
4 IP network 5 Existing public telephone network (PSTN)
6 IP phone adapter (VoIP-TA)
7 IP telephone media exchange (PSTN-MGW)
8 Kanmon Exchange (IGS)
9 Subscriber switch (LS)
10 reception desk

Claims (18)

From the IP telephone signal conversion server side connected to the public telephone line network when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the transmission side of the IP telephone network A call back system in an IP phone for calling back,
A line holding means for holding a connection line of the public line network without transmitting a disconnection signal sent by the calling side to the called side when the number on the called side is a preset telephone number;
Call-back means for sending back a call-back signal to the caller based on the disconnection signal;
A call back system for an IP phone, comprising: The recall means is
2. The call back system for an IP phone according to claim 1, wherein the call back signal is sent back and a notification sound for notifying the callee that the call is being returned is sent. The notification sound is
The IP telephone call back system according to claim 2, wherein at least one of a voice announcement and a chime sound is present. The recall means is
The telephone number set beforehand based on the telephone number at the time of transmission with the call-back signal is selected and transmitted to the call-back destination as a caller telephone number. Call back system for IP phones. From the IP telephone signal conversion server side connected to the public telephone line network when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the transmission side of the IP telephone network A call back method in an IP phone for calling back,
The line holding means for holding the connection line of the public line network without transmitting the disconnection signal sent by the calling side to the called side when the number on the called side is a preset telephone number. Holding the connection line; and
Sending back the call-back signal by call-back means for sending back a call-back signal to the caller based on the disconnection signal;
A call back method for an IP phone, comprising: The recall means is
6. The call back method for an IP telephone according to claim 5, wherein the call back signal is sent back and a notification sound for notifying the callee that the call is being returned is sent. The notification sound is
The IP telephone call back method according to claim 6, wherein at least one of a voice announcement and a chime sound is included. The recall means is
The telephone number set beforehand based on the telephone number at the time of transmission with the call back signal is selected and transmitted to the call back destination as a caller telephone number. Call back method for IP phone. From the IP telephone signal conversion server side connected to the public telephone line network when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the transmission side of the IP telephone network A call back program in an IP phone for calling back,
The line holding means for holding the connection line of the public line network without transmitting the disconnection signal sent by the calling side to the called side when the number on the called side is a preset telephone number. Holding the connection line; and
Sending back the call-back signal by call-back means for sending back a call-back signal to the caller based on the disconnection signal;
A call back program for an IP phone, comprising: The recall means is
The IP telephone call back program according to claim 9, wherein the call back signal is sent back and a notification sound for notifying the callee that the call is being returned is sent. The notification sound is
The IP telephone call back program according to claim 10, wherein at least one of a voice announcement and a chime sound is included. The recall means is
The telephone number set beforehand based on the telephone number at the time of transmission with the call-back signal is selected and transmitted to the call-back destination as a caller telephone number. Call back program for IP phone.   The IP telephone call back program according to any one of claims 9 to 12, wherein the program can be executed by being installed on a server arranged on the IP network. From the IP telephone signal conversion server side connected to the public telephone line network when a call made from the IP telephone network to the public telephone line network via the IP telephone signal conversion server is disconnected at the transmission side of the IP telephone network A recording medium recording a recall program in an IP phone for recalling,
The line holding means for holding the connection line of the public line network without transmitting the disconnection signal transmitted by the caller side to the callee side when the callee number is a preset telephone number. Holding the connection line; and
Sending back the call-back signal by call-back means for sending back a call-back signal to the caller based on the disconnection signal;
A recording medium recording a call back program in an IP phone. The recall means is
15. The recording medium for recording a call back program in an IP telephone according to claim 14, wherein the call back signal is sent back and a notification sound for notifying the callee that the call is being returned is sent. The notification sound is
16. The recording medium recording a call back program in an IP telephone according to claim 15, wherein the recording medium is at least one of a voice announcement and a chime sound. The recall means is
The telephone number set beforehand based on the telephone number at the time of transmission with the call-back signal is selected and transmitted to the call-back destination as a caller telephone number. A recording medium that records a call back program in an IP phone. 18. The recording medium recording a call back program in an IP telephone according to claim 14, wherein the recording medium is installed in a server arranged on the IP network and can be executed.

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