JP2005318220A - Ip telephone coping with power failure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IP telephone, coping with power failures, in which an IP telephone function is switched to a PSTN telephone function on the occurrence of power failure during IP telephone service and the call is originated again. <P>SOLUTION: The IP telephone 1 having an IP telephone function and a PSTN telephone function which is to be connected, respectively, with an IP network and a PSTN network and dealing with power failure comprises an IP communication control section 11 performing IP communication, a PSTN communication control section 13 performing PSTN communication, a commercial power supply control function F14, a commercial power supply monitoring function F15, a connector for transmitting/receiving IP packet and PSTN analog data to/from a gateway unit; and a voice control circuit 12, having a voice select function F123 for connecting the PSTN communication control section 13 or the IP communication control section 11 selectively with a handset. When commercial power supply is unavailable, transition is made from IP communication to PSTN communication. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power outage-compatible IP telephone that constitutes an IP telephone system capable of making a call even during a power outage.

  In an IP telephone system connected to the Internet via a gateway, a telephone call cannot be made if a power failure occurs on the IP telephone.

  In order to solve such a problem, in a telephone having a LAN interface circuit and an analog interface circuit, when a status inquiry packet from a LAN private branch exchange is monitored for a predetermined time and a status monitoring packet is not received for a predetermined time, There has been proposed a LAN telephone that determines that a failure has occurred in a LAN and switches from a LAN interface to an analog interface (see, for example, Patent Document 1).

In the LAN telephone set described above, when it is determined that a failure has occurred in the LAN, the LAN interface is switched to the analog interface. However, no consideration is given to the case where the power supply of the telephone is cut off.
JP-A-10-272143

  The present invention relates to an IP telephone having an IP communication function for performing communication through an IP network and a PSTN communication function for performing communication through an analog network. When a power failure occurs during an IP call, the IP telephone function is An object of the present invention is to provide a power outage compatible IP telephone that can be switched to the telephone function and re-transmitted.

  In order to solve the above-mentioned problems, the present invention provides a power outage-compatible IP telephone that can cope with a power outage having an IP telephone function and a PSTN telephone function connected to the Internet (IP network) and a PSTN (analog) line. A power supply circuit that uses a power supply as a power supply, a power failure detection circuit that detects a power failure of a commercial power source, a connector that transmits and receives IP packets and analog data for PSTN to and from a LAN, a PSTN communication control circuit that performs PSTN communication, An IP communication control circuit that performs IP communication and a voice selection circuit that selects and connects a PSTN communication control circuit or an IP communication control circuit to the handset, and when there is no commercial power supply, shifts from IP communication to PSTN communication It is characterized by that.

  The present invention is characterized in that, in the power failure response IP telephone set, when it is detected that there is no commercial power supply, the power supply to the IP communication function is stopped and the power supply to the PSTN communication function unit is performed by the power from the PSTN line. And

  The present invention is characterized in that when a power failure occurs during an IP call in the power outage compatible IP telephone, the IP communication is switched to the PSTN communication, and the PSTN communication is re-transmitted to the other party who has been making the IP call.

  According to the present invention, when a power outage occurs during an IP call in the power outage compatible IP telephone set, it is determined whether there is a PSTN telephone number corresponding to the IP address of the other party with whom the IP call was made, and then PSTN communication is retransmitted. It is characterized by that.

  The present invention determines whether or not the PSTN communication is made after the PSTN communication is transmitted after the recovery from the power failure when the power failure that occurred during the IP call is an instantaneous power failure. In some cases, the IP communication is automatically retransmitted by returning from the PSTN communication to the IP communication.

  According to the present invention, when a power failure occurs during an IP call and the power failure returns after the power failure occurs during an IP call, the PSTN communication function is stopped and the IP communication function is enabled. Features.

  By providing the above configuration, the present invention can disconnect the IP call when a power failure occurs during the IP call, and can continue the call by re-sending the PSTN call to the other party that was in the IP call.

  The configuration of the power failure response IP telephone system according to the present invention will be described with reference to FIG. In the IP telephone system, the power failure compatible IP telephones 1a-1 and 1a-2 accommodated in the gateway apparatus 3a and the power failure compatible IP telephone 1b accommodated in the gateway apparatus 3b are connected to the Internet (IP network) and a PSTN (Public Switched Telephone). (Network: public telecommunications network: analog circuit network) 5. The line network 5 and the gateway device 3 are connected by an ADSL compatible PSTN line 51. The gateway device 3 and the power outage compatible IP telephone 1 are connected by an Ethernet (registered trademark) 53.

  With reference to FIG. 2, the functional configuration of the power failure response IP telephone according to the present invention will be described. The power failure compatible IP telephone 1 includes a PHY (Ethernet line control) function F111, an error control function F112, a MAC address control function F113, an IP packet control function F114, an IP packet buffer F115, and an IP communication control function F116. Voice packet control function F117, voice buffer F118, PSTN power supply circuit control function F131, PSTN line control function F132, AD / DA conversion function F133, PSTN communication control function F134, voice control function F121, AD / DA conversion function F122, voice selection function F123, commercial power supply control function F14, and commercial power supply monitoring function F15.

  The IP communication control unit 11 is configured by the PHYF 111 to the voice buffer F118, the voice control unit 12 is configured by the voice control function 121 to the voice selection function F123, and the PSTN communication control unit is configured by the PSTN power supply circuit control function F131 to the PSTN communication control function F134. 13 is configured.

  The PHYF 111 has a function of converting an electric signal from the Ethernet cable into a signal used in a circuit in the apparatus.

  The error control function F112 is a function for detecting a received packet error in the Ethernet signal converted by the PHYF 111 and generating transmission packet error information.

  The MAC address control function F113 is a function for adding and deleting the MAC address of the Ethernet packet.

  The IP packet control function F114 is a function for controlling transmission / reception information of IP packets.

  The IP packet buffer F115 is a function used for transmission / reception of IP packets. The voice has a plurality of buffers so that it can be transmitted and received at regular intervals. In the case of data, it has multiple large buffers so that large data will not overflow.

  The IP communication control function F116 is a function for performing communication control and communication information management such as IP packet dial information, call connection information, voice information, and timer management.

  The voice packet control function F117 is a function for converting and controlling the stored voice information and IP packets.

  The audio buffer F118 is a function for accumulating digitized audio information and a function for controlling the function.

  The PSTN power supply circuit control function F131 is a function for receiving power from the PSTN line and a function for controlling the function.

  The PSTN line control function F132 is a function for controlling line functions such as dialing, looping, and talking on the PSTN line.

  The AD / DA conversion function F133 is a function for digitizing the analog signal of the PSTN line, and is a function for converting the digital signal to analog.

  The PSTN communication control function F134 is a function that performs communication control necessary for communication using the PSTN line, and is a function that performs automatic retransmission control using IP packet communication records.

  The voice control function F121 is a function for controlling voice devices such as a voice input / output circuit, a speaker, a microphone, and a handset.

  The AD / DA conversion function F122 is a function that digitizes the analog signal from the voice control function F121, and is a function that converts the digital signal from the voice selection function F123 into analog.

  The audio selection function F123 is a function for selecting connection between the AD / DA conversion function F122 and the audio buffer F118 or the AD / DA conversion function F133.

  The commercial power supply control function F14 is a commercial power supply control function. When there is a commercial power supply, this function supplies power to all functional blocks other than the power supply monitoring circuit.

  The commercial power supply monitoring function F15 is a function that determines the presence or absence of a commercial power supply and controls the function block selection of the apparatus and the commercial power supply circuit or PSTN power supply circuit.

  The configuration of the voice selection function F123 will be described with reference to FIG. The voice selection function F123 includes a selector 123. The selector 123 can switch the route of the digital audio data with a selection function configured by a logic circuit. When a signal indicating that there is a commercial power supply is received from the commercial power supply monitoring function F15, a selection is made so that voice data communication can be performed between the voice buffer F118 and the AD / DA conversion function F122. When a signal indicating that there is no commercial power supply is received from the commercial power supply monitoring function F15, the AD / DA conversion function F133 and the AD / DA conversion function F122 are selected so that they can perform voice data communication with each other. That is, the voice selection function F123 switches between the AD / DA conversion function F133 and the voice buffer F118 in accordance with the commercial power status signal received from the commercial power monitoring function F15, and connects to the AD / DA conversion function F122 for mutual communication. .

  The flow of the power failure monitoring operation performed by the commercial power supply monitoring function F15 will be described with reference to FIG. When commercial power supply monitoring is started (S1), the commercial power supply monitoring function F15 is used to check whether power is supplied from the commercial power supply (S2). When commercial power is supplied, the commercial power supply circuit is activated by the commercial power control function F14 to supply power to the entire telephone (S3). Next, the PSTN power supply circuit control function F131 is stopped to stop the power of the PSTN function (S4). Next, the PHYF 111 to the voice buffer F118 and the voice control circuit unit F12 are activated to activate the IP telephone circuit (S5). In this state, it can be used as an IP phone (S6). In step S2, when there is no commercial power supply (for example, during a power failure), the commercial power supply control function F14 is first stopped (S7), and then the PSTN power supply circuit control function F131 is activated to start the PSTN line control functions Fl32 to PSTN. Power is supplied to the communication control function F134 and the voice control circuit unit F12 (S8), the power supply to the PHYF 111 to the voice buffer F118 is stopped, the IP communication function is stopped, and the power consumption of the telephone is suppressed (S9). In this state, it can be used as a PSTN telephone (S10).

  The circuit configuration of the gateway device 3 will be described with reference to FIG. The gateway device 3 includes a line connection connector 31, a splitter 32, a hybrid circuit 331, an ADSL signal conversion circuit 332, a LAN interface 34, a pulse transformer 341, a PHY (Ethernet control circuit) 342, an MPU 35, A ROM 36, a RAM 37, and a power supply circuit 38 are included.

  A line connection connector (for example, RJ11) 31 is a PSTN line and ADSL line connection connector. An ISDN line may be used instead of the PSTN line.

  The splitter 32 is a circuit that separates the PSTN signal and the ADSL signal.

  The hybrid circuit 331 is a 2-wire 4-wire signal conversion circuit.

  The ADSL signal conversion circuit 332 is a circuit that converts a digital signal from the MPU 35 into an ADSL communication signal, and a circuit that converts a signal from the ADSL into a digital signal.

  The LAN interface (for example, RJ45) 34 is a connector that uses the pin 1, pin 2, pin 3, and pin 6 lines for LAN lines, and the rest for PSTN lines. The PSTN line may be an ISDN line.

  The pulse transformer 341 is a circuit that insulates the DC component of the signal.

  A PHY (Ethernet control circuit) 342 is a circuit that controls an Ethernet line.

  The MPU 35 is a circuit that controls the entire gateway device 3.

  The ROM 36 is an electrically rewritable nonvolatile memory, and stores a program for controlling the entire circuit.

  The RAM 37 is a rewritable memory and is used for storing data during work.

  The power supply circuit 38 is a circuit that supplies a DC voltage of the circuit of the gateway device 3 and converts commercial power (AC voltage) to DC.

  The mode of line accommodation in the gateway device will be described with reference to FIG. The PSTN line and ADSL line connection connector 31 has pins 3 and 4 accommodating the PSTN lines L 1 and L 2 and connected to the splitter 32. The splitter 32 includes a high-pass filter 321 and a low-pass filter 322, and high-frequency components are connected to the hybrid circuit 331, and audio band signals and power are connected to pins 5 and 7 of the LAN interface 34. In the LAN interface 34, RX +, RX−, TEX +, and TX− are accommodated in the pin 1, pin 2, pin 3, and pin 6, respectively, are connected to the pulse transformer 341, and L1 and L2 are accommodated in the pin 5 and pin 7. . Since the PSTN signal is directly connected to the LAN, the gateway device 3 does not have to monitor the power failure.

  The hardware configuration of the power failure response IP telephone 1 will be described with reference to FIG. The power failure compatible IP telephone 1 includes a connector 181, a pulse transformer 182, a PHY 111, a PSTN line control circuit 132, a power failure detection circuit 15, an MPU 16, a ROM 171, a RAM 172, a composite CODEC 121, and a handset (HS) 191. A microphone (MIC) 192, a speaker (SPK) 193, a display (LCD) 194, a key (KEY) 195, and a power supply circuit 14.

  The connector (RJ45) 181 is a connector that is connected to the LAN interface 34 of the gateway device 3 and is separated by an Ethernet line and a PSTN line. The PSTN line may be an ISDN line.

  The pulse transformer 182 is a circuit that insulates the DC component of the signal.

  The PHY 111 is a circuit that controls the Ethernet line.

  The PSTN line control circuit 132 is a circuit that controls the PSTN line.

  The power failure detection circuit 15 is a circuit that monitors a commercial power source and detects a power failure state.

  The MPU 16 is a circuit that controls the entire IP telephone for power failure.

  The ROM 171 is an electrically rewritable non-volatile memory that stores a control program for the entire telephone and also stores an IP address and PSTN telephone information.

  The RAM 172 is a rewritable memory.

  The composite CODEC 121 is a circuit that performs voice control of a handset 191, a microphone 192, a speaker 193, a ring tone, and the like.

  The handset 191 is a circuit that converts transmission / reception audio and electrical signals to each other.

  The microphone 192 is a circuit that captures audio around the telephone and is used hands-free.

  The speaker 193 outputs sound from the PSTN line, handset, and hands-free.

  The display 194 is a means for displaying various information, and is composed of an LCD (liquid crystal display), but may be composed of LEDs.

  A key 195 is a circuit that captures key press information.

  The power supply circuit 14 is a power supply circuit that converts AC power from a commercial power source into DC power and supplies it to the telephone. In the event of a power failure, power from the PSTN line is supplied into the telephone.

  The configuration of the power supply circuit 14 will be described with reference to FIG. The power supply circuit 14 includes a PSTN power supply circuit 141, a commercial power supply control circuit 142, diodes 143, 144, 145, and a capacitor 146. The power supply circuit 14 selectively controls the operations of the PSTN power supply circuit 141 and the commercial power supply control circuit 142 by the power supply control signal from the detection result of the power failure detection circuit 15.

  The PSTN power supply circuit 141 is a circuit that extracts power from the PSTN line.

  The commercial power supply control circuit 142 is a circuit that extracts power from the commercial power supply.

  The diode 143 is a circuit that supplies power necessary for the PSTN function, and also supplies it to the audio control circuit unit F12.

  The diode 144 is a power supply collision prevention circuit that prevents the power supply from the diode 143 and the diode 145 from colliding with each other. When there is a commercial power supply, the commercial power supply is used as a PSTN function power supply.

  The diode 145 is a power supply for the IP telephone function.

  The capacitor 146 is a smoothing capacitor.

  A call sequence in the power failure response IP telephone system having the above configuration will be described with reference to FIG. FIG. 9 shows an IP communication sequence (normal) using SIP. When there is a commercial power supply, the power failure response IP phone a makes an IP phone call (INVITE) to the power failure response IP phone b (S21). An INVITE reception is notified from the power failure response IP telephone b (100 Trying) (S22), and a call is indicated from the power failure response IP telephone b (180 Ringing) (S23). A response is shown from the power failure-response IP telephone b (200 OK) (S24)). A response confirmation (ACK) is notified from the power failure-response IP telephone set a that has received the response (S25). The power failure response IP phone a and the power failure response IP phone b are in a voice call state, and a voice call is performed between them (S26). When the call is finished, a disconnection (BYE) process is executed from the power failure compatible IP telephone a (S27). Disconnection is completed (200 OK) from the IP telephone b for power failure (S28). In this way, connection and disconnection of a voice call by IP communication are performed.

  With reference to FIG. 10, a PSTN communication sequence in the case where a power failure occurs during an IP call and a transition to a PSTN call is followed by disconnection in the power failure state will be described. Until the voice call, the sequence from step S21 to step S25 of the IP communication sequence using the SPI shown in FIG. 9 is applied. If a power failure occurs in any of the power failure compatible IP phones a, for example, a power failure response IP phone a, during a voice call by IP communication between the power failure response IP phone a and the power failure response IP phone b (S31), the power failure response IP phone a and the power failure response The IP call between the IP telephones b is interrupted and the line is disconnected (S32). The power failure response IP telephone a detects the power failure, stops the IP call function and enables the PSTN communication function to switch from the IP telephone to the PSTN telephone (S33), and dials the power failure response IP telephone b on the PSTN line by the PSTN function. Make a call (S34). The power failure response IP telephone b receives the incoming call and responds (S35). When the communication path is established, a voice call by PSTN communication is performed between the two (S36). When the call ends, for example, the power failure-response IP telephone a disconnects the PSTN line (S37). When the power failure compatible IP telephone b is disconnected, the call is terminated (S38). In this way, when a power failure occurs during a voice call by IP communication, it is possible to shift to PSTN communication.

  A communication sequence from the occurrence of a power failure during an IP call to a PSTN call to the end of the call after the power failure is restored will be described with reference to FIG. The voice call by IP communication (S41) to the voice call by PSTN communication (S46) are performed in the same manner as steps S31 to S36 in FIG. In step S46, when the power is restored in a state where a voice call by PSTN communication is being performed between the power outage compatible IP telephone a and the power outage compatible IP telephone b (S47), the power outage corresponding IP telephone a recovers. Even then, the PSTN communication is continued (S46). When the call is finished, the power failure-response IP phone a disconnects the PSTN communication (S48). The power failure corresponding IP telephone b disconnects the PSTN communication (S49). The power failure response IP phone a confirms that the PSTN call has ended (S50), and when the PSTN communication is ended, enables the IP phone function, and then becomes an IP phone (S51). In this way, after a power failure occurs during a call by IP communication and then a transition to a voice call by PSTN communication is made, when the power failure is restored, the IP phone can be automatically restored after the PSTN call ends.

  With reference to FIG. 12, a PSTN automatic outgoing call resumption sequence for automatically making a PSTN communication and restarting the call after a power failure occurs during an IP call will be described. 11 is performed in the same manner as in the example of FIG. 11 until a power failure-response IP telephone set a switches from an IP telephone to a PSTN telephone after a power failure occurs after a voice call by IP communication (S41). When the IP communication is disconnected, the power failure handling IP telephone b determines whether the other party is disconnected or self-disconnected, and disconnects the IP line if the other party is disconnected (S61). If the other party is disconnected, the PSTN automatic response is enabled. (S62). The power failure response IP telephone a checks whether or not there is a PSTN telephone number corresponding to the IP address with which the IP call has been made (S63). If there is, the call is automatically re-sent to the PSTN telephone number (S64). The power failure-response IP telephone set b that has received the call confirms whether IP communication has been received from the same party within a time that is a predetermined time after the incoming call (S65). If there is no incoming IP communication within a certain period of time or if the other party is different, the PSTN incoming state is entered (S69). In step S65, if there is an incoming IP communication from the power failure compatible IP telephone a, an automatic response is made to reconnect (S66). Voice communication using PSTN communication can be performed between the two (S67). If there is no PSTN telephone number corresponding to the IP address in step S63, the power failure handling IP telephone a enters a standby state (S68). In this way, even if a power failure occurs and the call is disconnected during a voice call based on IP communication, it can be automatically re-transmitted to PSTN communication.

  With reference to FIG. 13, a commercial power supply instantaneous interruption return sequence when a power failure (commercial power supply interruption) occurs during an IP call will be described. A power failure occurs from a voice call by IP communication (S41), the power failure handling IP phone a shifts from an IP phone to a PSTN phone (S43), and checks whether the power failure handling IP phone b is disconnected or not so that PSTN automatic response is possible. Up to the process (S62) is performed in the same manner as in FIG. After the power failure compatible IP telephone a is switched from the IP phone to the PSTN phone, the power is restored when the power failure is restored (S71). The power failure compatible IP telephone a checks whether a PSTN call has been made to the other party who has been making the IP telephone call (S72). If the power failure is restored before the call is made, the power failure response IP telephone a switches from the PSTN telephone to the IP telephone (S73). If the PSTN call is made, the dial call in step S64 in FIG. 12 is executed. Confirmation of power recovery or before transmission may be performed using a timer. The power failure compatible IP telephone a confirms that a power failure occurred during a call (S74). If the power is not cut off during a call, the power failure-response IP phone a enters a standby state (S79). If the call is disconnected during a call, automatic IP re-transmission is performed from the power failure-response IP telephone a to the communication partner before the power failure (S75). The power failure-response IP telephone set b that has received the IP re-transmission confirms whether it has received an incoming call from the same party within a predetermined time (S76). If not, the call is received (S80). When the call is re-sent from the same party, the power failure response IP telephone b automatically responds as an IP telephone (S77). Thereafter, a voice call by IP communication is performed between the two (S78).

  As described above, according to the present invention, even when a power failure occurs during an IP call, when the voice communication is resumed by switching to PSTN communication or when the power failure is an instantaneous interruption, If so, the voice call by IP communication can be resumed, and if the PSTN automatic call has been made, the voice call by PSTN communication can be resumed.

The figure explaining the outline | summary of a structure of the IP telephone system corresponding to a power failure concerning this invention. The figure explaining the outline | summary of the function structure of the power failure response IP telephone which comprises the power failure response IP telephone system concerning this invention. The figure explaining the structure of the audio | voice selection function of the IP telephone set corresponding to a power failure shown in FIG. The flowchart explaining the power failure monitoring operation | movement in a power failure response IP telephone. The figure explaining the outline | summary of the hardware constitutions of the gateway apparatus which comprises the power failure corresponding IP telephone system concerning this invention. The figure explaining the circuit | line accommodation aspect of the gateway apparatus shown in FIG. The figure explaining the outline | summary of the hardware constitutions of a power failure response IP telephone. The figure explaining the specific structure of the power supply circuit of the IP telephone set corresponding to a power failure shown in FIG. The figure explaining the IP communication sequence between the power failure response IP telephones in the power failure response IP telephone system concerning this invention. The sequence diagram explaining the transfer process to PSTN communication when a power failure occurs during an IP call between power failure compatible IP telephones. The sequence diagram explaining the process of a power failure recovery | restoration at the time of cut | disconnecting PSTN after transfering to PSTN communication when a power failure generate | occur | produces during the IP telephone call between IP telephones corresponding to a power failure. The sequence diagram explaining the transfer process to PSTN communication when a power failure occurs during an IP call between power failure compatible IP telephones. The sequence diagram explaining the transfer process to PSTN communication or the return process to IP communication when an instantaneous power failure occurs during an IP call between IP telephones corresponding to a power failure.

Explanation of symbols

1 IP phone for power failure 11 IP communication control unit 111 PHY
12 Voice control circuit part 121 Composite CODEC
123 selector 13 PSTN communication control unit 132 PSTN line control circuit 14 power supply circuit 141 PSTN power supply circuit 142 commercial power supply circuit 143 to 145 diode 146 capacitor 15 power failure detection circuit 16 MPU
171 ROM
172 RAM
181 LAN connector 182 pulse transformer 191 handset 192 microphone 193 speaker 194 display 195 key 3 gateway device 31 connector 32 splitter 321 high-pass filter 322 low-pass filter 331 hybrid circuit 332 ADSL signal conversion circuit 34 LAN interface 341 pulse transformer 342 PHY
35 MPU
36 ROM
37 RAM
38 Power supply circuit 5 IP / PSTN network 51 ADSL compatible PSTN line 53 Ethernet
F111 PHY function F112 Error control function F113 MAC address control function F114 IP packet control function F115 IP packet buffer F116 IP communication control function F117 Voice packet control function F118 Voice buffer F121 Voice control function F122 AD / DA conversion function F123 Voice selection function F131PSTN Power circuit control F132 PSTN line control function F133 AD / DA conversion function F134 PSTN communication control function F14 Commercial power control function F15 Commercial power monitoring function

Claims (6)

In a power outage-compatible IP telephone that can cope with a power outage having an IP telephone function and a PSTN telephone function connected to an IP network and a PSTN line,
A power supply circuit using a commercial power supply,
A power failure detection circuit for detecting a commercial power failure,
A connector for transmitting and receiving IP packets and PSTN analog data to and from the gateway device;
A PSTN communication control circuit for performing PSTN communication;
An IP communication control circuit for performing IP communication;
A voice selection circuit for selecting and connecting a PSTN communication control circuit or an IP communication control circuit to the handset;
An IP telephone set for power failure characterized by shifting from IP communication to PSTN communication when there is no commercial power supply.   2. The power failure response IP phone according to claim 1, wherein when the absence of commercial power is detected, the power supply to the IP communication function is stopped and the power supply to the PSTN communication function unit is performed by the power from the PSTN line. Power outage IP phone.   3. The power outage compatible IP telephone set according to claim 1 or 2, wherein when a power outage occurs during an IP call, the IP communication is switched to the PSTN communication, and the PSTN communication is retransmitted to the other party who has been making the IP call. Power outage IP phone.   4. If a power outage occurs during an IP call in the power outage-compatible IP telephone set forth in claim 3, it is determined whether there is a PSTN telephone number corresponding to the IP address of the other party with whom the IP call was made, and then PSTN communication is retransmitted. A power outage-compatible IP phone.   4. The power outage compatible IP telephone according to claim 3, wherein when a power outage that occurred during an IP call is an instantaneous power outage, it is determined whether or not PSTN communication has been transmitted after power failure recovery, and before PSTN communication transmission. An IP telephone set for power failure, characterized in that at some time, IP communication is automatically retransmitted by returning from PSTN communication to IP communication. 4. The power failure response IP phone according to claim 3, wherein when a power failure occurs during an IP call and the power failure is restored after the transition from IP communication to PSTN communication, the PSTN communication function is stopped and the IP communication function is enabled. Features a power outage IP phone.

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