JP2005094225A - Communication terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication terminal device capable of solving a problem of erroneously using a public telephone line network without knowing that the connection is automatically switched to the IP network even when connected to the public telephone line network. .
A communication terminal device includes connection switching means for switching connection between an IP network and a public telephone line network, off-hook means for capturing a communication network by off-cooking, and dial tone detection means for detecting a dial tone. The off-hook means captures the public telephone line network by off-hooking, the public telephone line network transmits a dial tone by capturing the public line network by the off-hook means, and the connection switching means includes: When the dial tone detecting means detects the dial tone, the connection is switched from the public telephone network to the IP network.
[Selection] Figure 6

Description

  The present invention relates to a communication terminal device such as an IP phone, an IP phone adapter, and an IP video phone, and in particular, even when connected to a public telephone line network, the connection is automatically switched to the IP network network, so The present invention relates to a communication terminal device that can solve the problem of using the public telephone line by mistake.

Currently, IP phones are spreading at an explosive rate. There is an IP telephone adapter as a device for connecting to an IP network using a general telephone that has been used by connecting to a general subscriber line network. An IP telephone adapter has a function of connecting to an IP network and a general subscriber telephone network. There are various methods for determining which network to connect to, and the method is determined by the specifications of the IP telephone adapter. Usually, it is cheaper to communicate by connecting to an IP network. Therefore, when making a call, it is set to connect to the IP network unless a special operation is performed. For this reason, it is normal to be connected to the IP network even in a standby state.
The prior art includes: JP 2002-158799 (In order to determine the type of a telephone line connected to a telephone line connection port, first, SW is turned on to detect the presence or absence of a dial tone, and if a dial tone is detected, an analog telephone line is established. If it is not detected, the SW is turned off and the SW is turned on, the TE layer activation sequence is executed, and if synchronization can be established by this TE layer activation sequence, it can be determined that the ISDN line is used. If it cannot be established, it is determined that the line is not connected, and if it is determined that it is an analog telephone line, only SW is turned on, and if it is determined that it is an ISDN line, only SW is turned on. JP, 2002-158847, A (System controller that holds sound data of sound generated in G3 facsimile communication in a real-time network facsimile apparatus connected to an IP network, and outputs the sound data after D / A conversion. When an image data packet is communicated via an IP network with a voice codec and speaker, the sound data held in the system control unit is transferred to the voice codec according to the IP communication sequence, and the sound of the G3 facsimile communication is sent. Generated by a speaker).
JP 2002-158799 A JP 2002-158847 A

On the other hand, when receiving a call from a general public line, it is necessary to switch the connection from the IP network to the general public line. As a problem in this case, it is necessary to return the connection to the IP network again at which point.
In other words, when a call signal arrives from the general public network, the handset is usually off-hook, the call starts in response to the incoming call, and the connection is returned to the IP network when the call ends on-hook. However, if the other party answers the call while not responding to the call signal, the call signal stops. In this case, it is a problem as to when to return the connection to the IP network.
Conventionally, the connection is switched to the IP network after a certain period of time has elapsed since the call signal simply stopped (a longer time setting is required to ensure that the call signal has completely stopped). .
However, if the user makes a phone call before switching, the connection remains as a general public line, so he intends to make a call via the IP network, but is actually calling via the general public line. A bug actually occurred.
The present invention is for solving such problems, and even when connected to a public telephone line network, the connection is automatically switched to the IP network, so that the public telephone line is mistakenly noticed without being noticed. It is an object of the present invention to provide a communication terminal device that can solve a problem of using a network.

In order to achieve the above-mentioned object, the invention according to claim 1 detects connection tone switching means for switching the connection between the IP network and the public telephone line network, off-hook means for capturing the communication network by off-cooking, and dial tone detection. In the communication terminal device comprising a dial tone detection means, the off-hook means captures the public telephone line network by off-hooking, and the public telephone line network dials by capturing the public line network by the off-hook means. A tone is transmitted, and the connection switching means switches the connection from the public telephone line network to the IP network when the dial tone detection means detects the dial tone.
According to a second aspect of the present invention, there is provided connection switching means for switching connection between an IP network and a public telephone line network, off-hook means for capturing a communication network by off-cooking, and dial tone detection means for detecting a dial tone. In the communication terminal apparatus, the connection switching means is connected to the IP network in a standby state, and when a call signal from the public telephone line network is detected, the IP network network to the public telephone line network. When the connection is switched and the off-hook means goes off-hook immediately after the call signal stops without responding to the call signal, the off-hook means captures the public telephone line network. The dial tone is transmitted by capturing the public line network by means, and the connection switching Stage, the if the dial tone detecting means detects the dial tone, characterized in that switching the connection from the public switched telephone network to the IP network.
According to a third aspect of the present invention, the communication terminal apparatus according to the first or second aspect further comprises dial tone transmission means for transmitting a dial tone, and the connection switching means is connected from the public telephone line network to the IP network. When the connection is switched, the dial tone sending means sends a dial tone.
According to a fourth aspect of the present invention, in the communication terminal apparatus according to the third aspect, the dial tone transmission means transmits a signal different from a dial tone transmitted by the public telephone line network.
According to a fifth aspect of the present invention, the communication terminal device according to any one of the first to fourth aspects further comprises dial number detecting means for detecting a dial number transmitted by the own device, wherein the dial tone detecting means is the dial tone. When the dial number detecting means detects a dial number sent to the public line network by the own device, the connection switching means continues the connection to the public telephone line network. Features.

According to a sixth aspect of the present invention, in the communication terminal device according to the fifth aspect, when the dial number detecting means detects a dial number that is not a dial number transmitted from the own device to the public line network, The connection switching means switches the connection from the public telephone line network to the IP network.
Further, in the communication terminal device according to any one of claims 1 to 6, the connection switching means is configured so that when the dial tone detecting means detects the dial tone, the connection switching means is connected to the public telephone line network. While switching the connection to the IP network, the dial number detecting means switches the connection from the IP network to the public telephone line when the dial number detecting unit detects a dial number transmitted to the public line. It is characterized by.
Further, in the communication terminal device according to any one of claims 1 to 7, the invention according to claim 8 transmits a warning sound when the dial tone detecting means detects a dial tone from the public telephone line network. Or a warning means for displaying warning information.
The invention according to claim 9 is characterized in that the communication terminal device according to any one of claims 1 to 8 is an IP telephone.
The invention according to claim 10 is characterized in that the communication terminal device according to any one of claims 1 to 8 is an IP telephone adapter.

According to the first and second aspects of the present invention, since the connection is automatically switched to the IP network even if it is connected to the public telephone line network, there is a problem that the public telephone line network is mistakenly used without being noticed. Solvable.
According to the third and fourth aspects of the present invention, since the dial tone different from the dial tone transmitted by the exchange of the public telephone line network is transmitted, the user can be surely connected to the IP network.
According to the invention of claim 5, when the telephone number needs to be connected to the public telephone line network, automatic switching to the IP network can be prevented.
According to the sixth aspect of the present invention, when connection to the public telephone line network is not necessary, connection to the IP network can be quickly switched.
According to the invention of claim 7, even when the connection to the IP network is switched, the connection is automatically switched to the public telephone line network, so that the user does not have to be aware of the network to which the user is connected.
According to the invention of claim 8, unintended use of the public telephone line network can be prevented by the warning sound.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an IP telephone as a communication terminal apparatus embodying the present invention.
As shown in FIG. 1, in this IP phone, a CPU (Central Processing Unit) 1 controls the entire apparatus, and its execution program is stored in a ROM (Read Only Memory) 3. The execution program is read from the ROM 3, and the instructions contained in the execution program are sequentially interpreted to control the entire apparatus. A RAM (Random Access Memory) 5 forms a work area necessary for the control, and stores storage parameters, various parameters necessary for the control, management information, and the like.
The operation input / display unit 7 includes a display for displaying various operation keys, operation guidance, and the like, and is for an operator to operate the apparatus. The handset 9 is a so-called receiver that performs a voice call, and includes a speaker that outputs voice, a microphone that inputs voice, and the like. The call circuit 11 sends a voice signal input from a microphone or the like to the NCU unit 15 or the IP unit 17 through the connection switching unit 13, and conversely input from the NCU unit 15 or the IP unit 17 and passes through the connection switching unit 13. An audio signal is output to a speaker of the handset 9 or the like. In addition, the call circuit 11 generally includes a circuit that adjusts the volume by amplifying or attenuating the audio signal or improving the sound quality by changing the frequency characteristics of the audio signal. It is. In general, so-called side-tone control for controlling the sound wraparound from the transmitter to the receiver is also performed in this portion.
The IP unit 17 is used when connecting to an IP network. The IP unit 17 converts the analog audio signal sent from the call circuit 11 into digital data, and further encodes and compresses it if necessary. Next, the audio signal data is embedded in the IP packet for transmission, and sequentially sent out to the line connection I / F 19. Also, the audio signal data is taken out from the receiving IP packet input from the line connection I / F 19, is decoded and decompressed if necessary, and further converts the digital audio signal data into an analog audio signal. Send it out.
The IP unit 17 also assembles control IP packets for performing call control, sequentially sends them out to the line connection I / F 19 and disassembles the received control IP packets input from the line connection I / F 19. Such sending and receiving of the control IP packet may be configured by another means independent of the IP unit 17. The operation control of the IP unit 17 is performed by the CPU 1.

The NCU unit 15 is used when connecting to a public telephone line network. The NCU unit 15 includes an off-hook unit 15a for passing a direct current to capture a line due to an off-hook operation of the handset 9, a dial tone detection unit 15b for detecting a ringing signal from an exchange, an analog voice signal, and a primary side ( It is composed of a transformer portion 15c that electrically insulates the circuit side) from the circuit side. The NCU unit 15 sends an analog voice signal sent from the call circuit 11 to the line connection I / F 19 and sends an analog voice signal inputted from the line connection I / F 19 to the call circuit 11. The dial tone detection unit 15b can be composed of an analog operational amplifier (for signal amplification), a comparator (binarization and digitization), and a frequency counter (measures the frequency of the signal).
The connection switching unit 13 performs an operation of switching the connection so that the NCU unit 15 is selected when the public telephone line network is used and the IP unit 17 is selected when the IP network is used. Specifically, the connection switching unit 13 can be configured by a switch element such as a mechanical relay or a semiconductor relay, or a software switch that is switched by software. Further, the connection switching unit 13 may be arranged between the NCU unit 15 or the IP unit 17 and the line connection I / F 19 in addition to the arrangement shown in FIG.
The line connection I / F 19 sends a transmission IP packet input from the IP unit 17 to the IP network, and sends a reception packet input from the IP network to the IP unit 17. The line connection I / F 19 sends an analog voice signal input from the NCU unit 15 to the public telephone line network, and sends an analog voice signal input from the public telephone line network to the NCU unit 15. When a public telephone line network supplied by NTT or the like is used as a connection line, an XDSL modem that mutually converts a digital signal and an analog signal is included in the VoIP means. If the connection line is a LAN or the like, the line connection I / F 19 is a LAN I / F (Ethernet (registered trademark), token ring, FTTH, etc.). Moreover, you may provide both.
As shown in FIG. 1, the CPU 1, the ROM 3, the RAM 5, the operation input / display unit 7, the IP unit 17, and the call circuit 11 are connected to each other by an internal bus 21. Also. A dial tone transmission unit 23 and a dial number detection unit 25 are connected to the connection switching unit 13.

FIG. 2 is a schematic block diagram of an IP telephone adapter embodying the present invention.
The IP telephone adapter shown in FIG. 2 has the same configuration except that the telephone connection I / F 27 is provided instead of the telephone circuit 11, the handset 9, and the transformer unit 15c in the IP telephone shown in FIG. . The telephone connection I / F 27 is an analog I / F for connecting to a general telephone, and inputs / outputs an analog audio signal.
FIG. 3 is a schematic block diagram of an IP videophone embodying the present invention.
The IP videophone shown in FIG. 3 has a configuration in which an image processing circuit 29, an image display unit 31, and a camera 33 are added to the IP phone shown in FIG. The camera 33 converts the subject into image data one after another. The image data is subjected to image processing for transmission data by the image processing circuit 29. The image-processed data is encoded and compressed by the IP unit 17, and the image signal data is embedded in a transmission IP packet and sequentially sent to the line connection I / F 19. Further, the image signal data is extracted from the IP packet for reception input from the line connection I / F 19, decoded and decompressed, and sent to the image processing circuit 29. The image processing circuit 29 performs image processing in accordance with the image display unit 31 and sends image data to the image display unit 31. The image display unit 31 obtains a moving image by continuously displaying the image data. I can do it.
Note that the sequence, operation, and the like when making a call by connecting to a public telephone line network are generally well known, and thus description thereof is omitted here.

Next, referring to FIGS. 4 and 5, a protocol used in an IP phone or the like will be described.
The call setting means sets a call using a standard call control protocol (SIP, H.323, MEGACO, etc.) defined by the standard, and enables communication or a call.
FIG. 4 is a diagram showing a SIP protocol stack used in an IP phone or the like.
As shown in FIG. 4, when SIP is used as a call / session control protocol, IP (Internet Protocol) is used in the network layer. In this case, UDP (User Datagram Protocol), TCP (Transmission Control Protocol), or SCTP (Stream Control Transmission Protocol) is used in the Transport Layer. In this case, SDP (Session Description Protocol) is used as a control information description protocol for describing the SIP message. In this case, RTP (Realtime Transport Protocol) is used as a moving image / audio transmission / reception protocol together with UDP (transport layer).
FIG. 5 is a protocol diagram of one of the SIP communication models used in IP phones and the like.
First, a request message called INVITE is sent from the calling side. INVITE is a session activation signal, and an attribute of the session that can be received by the caller is indicated by SDP. Specifically, the reception condition (codec, port number, etc.) on the calling side and the transmission condition are presented. The called party receives the INVITE and sends 180 Ringing to the calling party to notify that it is in the ringing state. The 180 Ringing may present the receiving condition (codec, port number, etc.) and the transmission condition on the called side, but is usually presented in the next 200 OK. Next, 200 OK is transmitted to the calling side in order to notify that the called side is ready to talk. The session attributes that can be received by the callee are indicated by SPD. This 200 OK presents the reception condition (codec, port number, etc.) and transmission condition on the called side.
Next, the calling side transmits ACK to the called side, thereby negotiating attributes that can be used for communication. In the present invention, this is defined as the connection phase for convenience. Next, transfer of media (sound, image, video, etc.) is started. In the present invention, this data transfer period is defined as a data transmission / reception phase for convenience. When terminating the communication, the stop side sends a BYE signal to request the end of the communication, and the side receiving it transmits a 200 OK signal as a response to terminate the communication. In the present invention, this phase is defined as a cutting phase for convenience.

FIG. 6 is an operation flowchart of the IP telephone shown in FIG. This operation control is mainly performed by the CPU 1.
In step 101 of FIG. 6, the connection switching unit 13 selects an IP network in a normal standby state. This is because the IP network is usually used more frequently because the telephone fee is lower when using the IP network when making a call.
Next, when a partner apparatus other than the IP telephone makes a call, a call signal arrives from the public telephone line network (step 103). At this time, when the calling signal detection unit detects the calling signal and notifies the CPU 1 or the connection switching unit 13 of the result, the connection switching unit 13 instructed by the CPU 1 connects to the public telephone line network from the IP network. Are switched (step 105).
Next, in this state, it is determined whether or not the user picks up the handset in response to the calling signal from the partner device (step 106). In this case, the user usually picks up the handset (step 106). 106 Yes) The off-hook portion 15a performs an off-hook operation. That is, the line is closed by flowing a direct current output from the line to the NCU unit 15. The circuit is closed by a mechanical relay or a semiconductor relay, and the direct current is passed through a transformer or a semiconductor circuit configured to pass a current. Whether the handset is lifted can be detected by providing a mechanical switch on the cradle side where the handset is placed. When the mechanical switch lifts the handset, it outputs an off-hook signal, and the CPU 1 detects this and closes the line. If the handset itself has an off-hook portion 15a, when the handset is lifted, the DC current circuit inside the handset flows the DC current from the line and directly closes the line. The off-hook unit 15a may also include a current detection unit that detects whether a direct current actually flows.
When a direct current flows and the line is closed, the call is answered and a call is started (step 107). When the call is finished, the user hooks the handset on, so that the off-hook unit 15a cuts off the direct current from the line and opens the line (step 109). The connection switching unit 13 detects this on-hook, that is, detects the interruption of the direct current, and switches the connection from the public telephone line network to the IP network.

  However, in some cases, the call signal may not be answered (No in step 106). In this case, the partner apparatus continues the call, but if this does not answer the call, the call is interrupted (step 111). As a result, the call signal to the called party (own device) is stopped. At this time, in order to switch the connection from the public telephone line network to the IP network, the connection switching unit 13 runs a timer for a certain period of time to measure the switching time (step 113). Then, while the ringing signal is stopped and the timer is running, it is determined whether the user has off-hooked the handset to make a call (step 115). If the handset is not off-hooked to make a call (No in step 115), after a certain period of time has elapsed, the connection is switched to the IP network, the device returns to the standby state, and then receives a call or call. The operation is ready (step 117).

On the other hand, if the ringing signal is stopped and the user goes off-hook to make a call before the predetermined time elapses (Yes in step 115), the connection switching unit 13 still selects the public telephone line network. Therefore, the public telephone line is closed and captured (step 119). When the line is closed, a dial tone signal which is a signal notifying that the dial signal is ready to be received is sent from the exchange on the public telephone line network side. The dial tone detector 15a detects the dial tone signal and notifies the CPU 1 or the connection switching unit 13 of the detection result directly. As a result, the connection switching unit 13 instructed by the CPU 1 switches the connection from the public telephone line network to the IP network (step 121).
At this time, the dial tone transmission unit 23 generates and transmits a dial tone signal (second dial tone signal) indicating that the IP network side is ready to receive a dial number in the apparatus (step 123). The dial tone on the IP network side transmits a signal that can be distinguished from a dial tone (usually a continuous tone of 400 Hz) transmitted by the exchange of the public telephone line network. Therefore, since the user transmits a dial tone different from the dial tone transmitted by the exchange of the public telephone line network, the user can be surely connected to the IP network.
The dial tone transmission unit 23 includes a frequency generator and an amplifier. For example, a signal having a frequency near 400 Hz and having cadence, a signal having a frequency far from 400 Hz, music, voice, and the like are conceivable.

At this time, it is determined whether or not the dial number detection unit 25 detects the transmission of the dial number to the public telephone line network generated by the own apparatus (step 125), and the connection to the public telephone line network generated by the own apparatus is determined. When transmission of the dial number is detected (Yes in step 125), the connection switching unit 13 switches the connection from the IP network to the public telephone line network (step 127). The dial number detection unit 25 detects a dial pulse type or DTMF type dial number. Specifically, in the case of a dial pulse, on / off of a direct current is detected, and a DTMF signal is detected by a DTMF receiver.
When the dial number detection unit 25 detects a dial number that is not the dial number that the device itself sends to the public line network (No in step 125), the connection switching unit 13 To switch to the IP network (step 129).

Even if the dial tone detector 15b detects the dial tone of the exchange, the dial number detector 25 does not immediately switch the connection to the IP network, but the dial number detector 25 dials the public telephone line network generated by the own device. When the transmission of the number is detected (Yes in step 125), the connection to the public telephone line network may be continued without switching the connection to the IP network.
At this time, if the dial number generated by the own device is not a dial to the public telephone line network, the connection is switched to the IP network. Whether the dial number generated by the own device is a dial to the public telephone line network may be provided with dial number type judging means for judging by the dial number. In actuality, the dial number type judging means judges by comparing the dial number inputted by the CPU 1 with the number stored in the memory. For example, in the case of numbers starting with 1 such as 110 and 119, it is determined that the call is to the public telephone network. A dedicated number for connecting to the public telephone line network such as 0000 can be determined in advance.
Further, a warning means is provided for notifying the user that the public telephone network is being used when the dial tone detector 15b detects the dial tone of the exchange. For example, it is conceivable that a warning sound (sound is generated from a buzzer, a speaker, etc.), warning information is displayed on a display unit, or a warning is given by light from an LED, a lamp, or the like.

FIG. 7 is a diagram showing the structure of a SIP control packet in a specific embodiment of the present invention. As shown in FIG. 7, the SIP control packet includes an IP header, a UDP (TCP) header, and a SIP message.
FIG. 8 is a diagram showing the structure of a SIP data packet in a specific embodiment of the present invention. As shown in FIG. 8, the SIP data packet includes an IP header, a UDP header, an RTP header, and audio / image data.
FIG. 9 is a diagram illustrating the structure of a UDP datagram in a specific embodiment of the present invention. As shown in FIG. 9, the UDP datagram includes a transmission port number, a destination port number, a data length, a checksum, and data.
FIG. 10 is a diagram illustrating the structure of an IP datagram used in SIP according to a specific embodiment of the present invention. As shown in FIG. 10, the configuration of the IP packet includes version information, header length information, service type information, total length information, identifier (ID), flag information, fragment offset information, liveness, and so on. It consists of time (TTL) information, protocol type information, header checksum information, a source address, a destination address, options, padding, and a data area.

As described above, the IP telephone is described as an example and SIP is used as an example of the standard protocol. There are H.323, HTTP, MEGACO, and the like, and the present invention can be implemented by other local protocols instead of the standard protocol.
In addition to the IP phone, the terminal device can be applied to an IP phone adapter (FIG. 2), an IP videophone (FIG. 3), an IP mobile phone, an IP mobile terminal device, an IP terminal device represented by an Internet fax, The present invention can also be applied to a standard protocol or a local protocol used in the terminal device.

1 is a schematic block diagram of an IP phone embodying the present invention. It is a schematic block diagram of the IP telephone adapter which implemented this invention. 1 is a schematic block diagram of an IP videophone embodying the present invention. It is a figure which shows the protocol stack of SIP used by IP telephone etc. FIG. It is one protocol figure of the communication model of SIP used by IP telephone etc. 3 is an operation flowchart of the IP telephone shown in FIG. It is a figure which shows the structure of the packet for SIP control in the specific Example of this invention. It is a figure which shows the structure of the packet for SIP data in the specific Example of this invention. It is a figure which shows the structure of the UDP datagram in the specific Example of this invention. It is a figure which shows the structure of the IP datagram used by SIP in the specific Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CPU, 3 ... ROM, 7 ... Display part, 9 ... Handset, 11 ... Call circuit, 13 ... Connection switching part, 15 ... NCU part, 15a ... Off hook part, 15b ... Dial tone detection part, 15c ... Transformer part, DESCRIPTION OF SYMBOLS 17 ... IP part, 21 ... Internal bus, 23 ... Dial tone transmission part, 25 ... Dial tone detection part, 25 ... Dial number detection part, 29 ... Image processing circuit, 31 ... Image display part, 33 ... Camera

Claims (10)

A communication terminal apparatus comprising connection switching means for switching connection between an IP network and a public telephone line network, off-hook means for capturing a communication network by off-cooking, and dial tone detection means for detecting a dial tone,
The off-hook means captures the public telephone line network by off-hooking, the public telephone line network transmits a dial tone by capturing the public line network by the off-hook means, and the connection switching means includes the dial A communication terminal apparatus for switching connection from the public telephone line network to the IP network when the tone detecting means detects the dial tone. A communication terminal apparatus comprising connection switching means for switching connection between an IP network and a public telephone line network, off-hook means for capturing a communication network by off-cooking, and dial tone detection means for detecting a dial tone,
The connection switching means is connected to the IP network in a standby state, and when detecting a call signal from the public telephone line network, the connection switching means switches the connection from the IP network network to the public telephone line network, and The means captures the public telephone line network when it goes off-hook immediately after the call signal stops without responding to the call signal, and the public telephone line network is connected to the public line network by the off-hook means. A dial tone is transmitted when the dial tone is captured, and the connection switching means switches the connection from the public telephone line network to the IP network when the dial tone detecting means detects the dial tone. Terminal device.   The communication terminal device further includes dial tone sending means for sending a dial tone, and when the connection switching means switches the connection from the public telephone network to the IP network, the dial tone sending means The communication terminal apparatus according to claim 1, wherein a tone is transmitted.   4. The communication terminal apparatus according to claim 3, wherein the dial tone transmission means transmits a signal different from a dial tone transmitted from the public telephone line network.   The communication terminal device further includes dial number detecting means for detecting a dial number transmitted by the own device, and when the dial tone detecting means detects the dial tone, the dial number detecting means 5. The communication terminal device according to claim 1, wherein, when a dial number to be transmitted to the line network is detected, the connection switching unit continues the connection to the public telephone line network.   When the dial number detecting means detects a dial number that is not a dial number sent from the device to the public line network, the connection switching means switches the connection from the public telephone line network to the IP network. The communication terminal device according to claim 5.   The connection switching means switches the connection from the public telephone line network to the IP network when the dial tone detection means detects the dial tone, while the dial number detection means determines that the own device is connected to the public line network. 7. The communication terminal device according to claim 1, wherein when a dial number to be transmitted to the network is detected, the connection is switched from the IP network to the public telephone network.   8. The apparatus according to claim 1, further comprising warning means for transmitting a warning sound or displaying warning information when the dial tone detecting means detects a dial tone from the public telephone line network. The communication terminal device according to claim 1.   The communication terminal apparatus according to claim 1, wherein the communication terminal apparatus is an IP phone.   The communication terminal apparatus according to claim 1, wherein the communication terminal apparatus is an IP telephone adapter.

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