KR20170047992A - Method for forwarding call and communication device therefor - Google Patents

Abstract

A method for switching a busy call between a NON-USIM terminal and a first terminal through a call path via a USIM terminal, the method comprising the steps of: Receiving a call connection request from the second terminal to the NON-USIM terminal, switching the call connected between the NON-USIM terminal and the first terminal to a wait call by the network API gateway (NAG) USIM terminal and the USIM terminal by setting a first call path between the NON-USIM terminal and the second terminal by the NAG, and setting a second call path between the USIM terminal and the second terminal by the NAG, Lt; RTI ID = 0.0 > 2 < / RTI > terminals.

Description

[0001] METHOD FOR FORWARDING CALL AND COMMUNICATION DEVICE THEREFOR [0002]

The present invention relates to a method for switching a busy call and a communication terminal for the same, and more particularly, to a method for switching a call between a NON-USIM terminal supporting a smart call forwarding service in a call forwarding service of a one number multi- And a communication terminal for switching a call in the call between the counterpart terminal and the counterpart terminal,

As is well known, a communication terminal (or portable terminal) such as a smart phone has a call transfer function as an additional service function. The call transfer (call transfer) Means a function for switching an ongoing call to a third subscriber, i.e., another communication terminal.

Accordingly, the users of the communication terminal can be provided with a service to switch (call forward) the call currently in communication with the counterpart terminal to the third party (third communication terminal) at any time by using the call transfer function have.

Also, there is a call forwarding service as another additional service function in the communication terminal. In this call forwarding service, an incoming call to the USIM terminal is switched to a NON-USIM terminal to which the communication chip (for example, USIM) Function.

Accordingly, a user of the USIM terminal can receive a service for making a call with a counterpart terminal through the NON-USIM terminal by converting the call received to the USIM terminal into a NON-USIM terminal previously designated by the USIM terminal.

Meanwhile, when a call is received from another terminal through a NON-USIM terminal during a call with a counterpart terminal, the other terminal is switched to a wait call, and a service is provided for making a call connection between the NON-USIM terminal and another terminal It is possible to satisfy various service desires of the terminal users more effectively, but at present, there is no suggestion of such a service model.

Korean Patent Publication No. 10-2010-0019760 (published on Feb. 19, 2010)

The present invention is characterized in that when a new call is received from the counterpart terminal B while the NON-USIM terminal is in a call with the counterpart terminal A using the call path via the USIM terminal, the call between the NON- And a call termination method for a call transfer service capable of establishing a call connection between the NON-USIM terminal and the counterpart terminal B, and a communication terminal for the same.

The problems to be solved by the present invention are not limited to those mentioned above, and another problem to be solved by the present invention can be clearly understood by those skilled in the art from the following description will be.

A method for switching a call during a call according to an aspect of the present invention includes the steps of receiving a call from a second terminal while a call is connected between the NON-USIM terminal and the first terminal through a call path via a USIM terminal, USIM terminal; switching a call connected between the NON-USIM terminal and the first terminal to an idle call by a network API gateway (NAG); receiving, by the NAG, USIM terminal establishes a first call path between the NON-USIM terminal and the USIM terminal and establishes a second call path between the USIM terminal and the second terminal, thereby establishing a call connection between the NON-USIM terminal and the second terminal The method comprising the steps of:

The present invention provides, in another aspect, a communication terminal for switching a call connected between a NON-USIM terminal and a first terminal to a stand-by call, wherein the NON-USIM terminal and the first USIM terminal and the second terminal when a call connection request from the second terminal to the NON-USIM terminal is received while a call is connected between the terminals, The switching unit switches a call connected between the NON-USIM terminal and the first terminal to an idle call, and transmits a first call between the NON-USIM terminal and the USIM terminal and a second call between the USIM terminal and the second terminal, USIM terminal and the second terminal by establishing a call connection to the NON-USIM terminal.

When a new call is received from a counterpart terminal B while the NON-USIM terminal is in a call with the counterpart terminal A using the call path via the USIM terminal, the call is switched to the wait call and the NON -Using the call connection between the USIM terminal and the counterpart terminal B, it is possible to effectively satisfy various service needs of the terminal users related to the call waiting call transfer service for the NON-USIM terminal.

FIG. 1 is a configuration diagram of a call processing network system suitable for realizing a busy call switching method for a call transfer service according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a main procedure for converting a call between a NON-USIM terminal and a counterpart terminal into an idle call according to the present invention.

First, the advantages and features of the present invention, and how to accomplish them, will be clarified with reference to the embodiments to be described in detail with reference to the accompanying drawings. While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. It is to be understood that the following terms are defined in consideration of the functions of the present invention, and may be changed according to intentions or customs of a user, an operator, and the like. Therefore, the definition should be based on the technical idea described throughout this specification.

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

FIG. 1 is a block diagram of a call processing network system suitable for realizing a busy call switching method of a call forwarding service according to an embodiment of the present invention, and includes two IP terminals 102 and 104, a communication terminal 106, (Network API Gateway) 108, the push server 110, the CSCF 112, the HSS 114, the TAS 116, the communication network 118, the counterpart terminal A 120 and the counterpart terminal B 122 .

Here, the TAS 116, the CSCF 112 and the HSS 114, which are blocked by a solid line and denoted by the reference A, may mean an IMS (IP Multimedia Subsystem) network, which may be an intelligent network or an intelligent network node Can be defined. Also, the counterpart terminal A can be defined as a first terminal, and the counterpart terminal B can be defined as a second terminal.

1, the IP terminal 102 includes a tablet terminal having a push function, that is, a tablet terminal without a communication chip (for example, a Universal Subscriber Identification Module (USIM) or a SIM (Subscriber Identification Module) (Or NON-SIM) terminal. The IP terminal 102 can be provided with a standby call transfer service of the smart call forwarding service provided according to the present invention without a communication chip. The smart forwarding application 1022 can be loaded (loaded). Here, the smart call forwarding application 1022 has a self-call function and can provide function control for an address book, a dialing menu, a microphone, a speaker, and the like.

The smart call forwarding application 1022 that can be selectively loaded (loaded / unloaded) into the IP terminal 102 may be implemented as a software application or a detachable hardware, And can be defined as the name of the incoming / outgoing call switching unit.

In addition, the smart call forwarding application 1022 installed in the IP terminal 102 is selectively activated (executed) only while a call for executing the smart call forwarding transition is provided, (A state in which the NAG and the notification channel (or the HTTP channel) are not maintained) in a situation in which a call route is not provided.

Here, keeping the smart call forwarding application 1022 in the standby mode when there is no call for smart call forwarding is not necessary, in order to prevent the channel resources from being wasted unnecessarily.

In other words, the smart call forwarding application 1022 installed in the IP terminal 102 can be defined as a call application for a call. For this purpose, various menu UIs (user interface) such as dialing, address book interface, microphone control, And the like can be provided.

The IP terminal 104 may be, for example, a terminal (NON-USIM terminal) that does not have a PC, an IP-TV, a communication chip (e.g., USIM or SIM) The IP terminal 104 is provided with a smart incoming call capable of performing the same or similar function as that of the IP terminal 102 in order to receive the call waiting call transfer service of the smart call forwarding provided according to the present invention, The conversion application 1042 can be mounted.

At this time, since the IP terminal 104 is a terminal that can not use the push function, a notification channel with the NAG 108 must be generated and maintained. To this end, the smart call diversion application 1042 mounted on the IP terminal is driven ), It can generate and maintain a notification channel with the NAG 108 by generating (calling) a notification API message including information such as a user ID, a device ID, an authentication token, etc. and transmitting the notification API message to the NAG 108. In other words, the IP terminal 104 may refer to a terminal that has already been generated and maintained before the call switch of the notification channel with the NAG 108.

Here, the smart call forwarding application 1042 installed in the IP terminal 104 may be set to be automatically executed when the power of the IP terminal 104 is turned on or when an operating system (operating program) is started (booted).

Next, the communication terminal 106 may be an HD voice terminal mounted with a communication chip (or a communication card), and may be defined as a USIM (or SIM) terminal. A module 1062 for HD voice communication (HDV) communication is mounted on the communication terminal 106 and an IP terminal (e.g., tablet, PC, IP-TV, etc.) (APP) 1064, that is, a smart call forwarding application 1064, which provides a call route required to provide a call transfer during a call.

Here, the smart call forwarding application 1064 that can be selectively loaded (loaded / unloaded) into the communication terminal 106 may be implemented as a software application or a detachable hardware form, , A calling switching unit, and a calling / receiving switching unit. Further, the communication chip mounted on the communication terminal 106 may mean, for example, a USIM card or a SIM card defined as a subscriber identity module.

At this time, the smart forwarding application 1064 installed in the communication terminal 106 selectively activates (executes) the IP terminal only during a call for a call forwarding service or during a call, (NAG and notify channel (or HTTP channel) is not maintained) in a case where the terminal does not provide a route for the call forwarding service or a standby call transfer during the call. Keeping the smart call forwarding application 1064 in the standby mode when there is no route to the IP terminal for a call forwarding service or for a standby call during a call is unnecessary waste of channel resources In order to prevent that.

The smart call forwarding application 1064 can generate a notification channel to the NAG 108 through a message exchange with the NAG 108 by activating when the push message is received from the push server 110. [ At this time, termination of activation of the smart call forwarding application 1064 (that is, switching to the standby mode) can be realized by a notification from the NAG 108 (call connection cancellation notification).

Accordingly, the smart call forwarding application 1064 installed in the communication terminal 106 may be defined as a management application for management rather than a call application for a call. For this purpose, a simple menu UI (user interface) A menu UI for setting (selecting) whether or not the activation of the service (the availability state of the smart call forwarding) or the inactivation of the smart call forwarding (the disabled state of the smart call forwarding) And a menu UI for turning on / off a function of switching a call signal of a counterpart terminal, which is in a call state, to a wait call when a call is received from the counterpart terminal.

On the other hand, the NAG (Network API Gateway) 108 makes the NON-USIM terminal (for example, the IP terminal 102) via the USIM terminal (e.g., the communication terminal 106) When a new call is requested (incoming call of a new call) from another counterpart terminal (for example, a counterpart terminal B) in a state of being in communication with the counterpart terminal A, for example, A function of generating a Telco Call Notification message and transmitting it to the smart call diversion application 1064 mounted on the communication terminal 106, which is a USIM terminal, .

At this time, the term 'telco' may refer to a call (outgoing call) generated from a private communication network (eg, SKT communication network) rather than a third party communication network. A telco call reception notification message is a message for providing a function of receiving a call reception of a telco from a USIM terminal (i.e., the communication terminal 106). To this end, the USIM terminal is connected to the NAG 108 in advance with a notification channel .

Here, the user ID may be an ID assigned to the user of the communication terminal 106, and the device ID may be assigned to the communication terminal 106 and each IP terminal (e.g., tablet, PC, IP-TV, etc.) May refer to one or more terminal IDs.

When the NAG 108 receives a relay call origination API message corresponding to the telco call reception notification message from the smart call forwarding application 1064, the NAG 108 generates a relay call incoming notification message, To the smart call forwarding application 1022 of the smart call forwarding application 102, for example. Here, the relay call origination API message may provide a function of originating a relay call from a NON-USIM terminal (IP terminal) to a USIM terminal or a function of a USIM terminal transmitting a relay call to a NON-USIM terminal (IP terminal) .

The NAG 108 also receives a telco call control transfer API message from the smart call forwarding application 1022 of the IP terminal 102 in response to the acceptance response of the new call, And delivering a Notification message to the smart call forwarding application 1064 of the communication terminal 106, for example.

Here, the telco call control transfer API message may include, for example, a user ID, a device ID, an authentication token, a relay call session ID, a telco call control information (hold) The control delivery notification message may include, for example, a service name, a relay call session ID, a telco call control information, and the like. The telco call control transfer API message includes a NON- And a function of requesting control of the telco call to the USIM terminal through the call, and the function of receiving the status of the telco call from the USIM terminal through the NL-USIM terminal via the relay call can be provided can do.

When the relay call acceptance API message is received from the smart call forwarding application 1022 of the IP terminal 102 at the time when the new call is accepted, the NAG 108 transmits a corresponding relay call acceptance notification message To the smart call forwarding application 1064 of the communication terminal 106, and so on. Here, the relay call admission API message may provide a function of accepting reception of a relay call at the USIM terminal and the NON-USIM terminal, and the relay call acceptance announcement message may be accepted when the relay call is accepted at the USIM terminal and the NON- It is possible to provide the function of receiving the message that the message has been received.

Further, the NAG 108 may set up (call setup) an RTP media path for a new call based on the API messages exchanged between the smart call forwarding application 1064 and the smart call forwarding application 1022 If the IP terminal 102 is in an NAT environment, it can form a call path via the NAG 108. In an environment where there is no NAT, the smart call forwarding application 1022 and the smart The call path between the call forwarding application 1064 and the call forwarding application 1064 can be connected by P2P.

When the push delivery request message including the push authentication token, the device ID, and the like is transmitted from the NAG 108, the push server 110 loads the smart call forwarding application and / or the communication terminal 106 installed in the IP terminal The smart-call forwarding application 1064 may generate a push message so that the smart-call forwarding application 1064 may be woken up and transmit the selected message to each smart call-forwarding application.

Next, a call session control function (CSCF) 112 in the IMS network A can be defined as a call session control node. The call session control function 112 performs call processing based on IMS, and performs a session initiation protocol (SIP) And basic functions for control.

The CSCF 112 also routes the re-INVITE message to the TAS 116 when it receives a re-INVITE message for waiting for an existing call from the NAG 108, For example, the SIP 200 OK message may be transmitted to the NAG 108 when it is received from the TAS 116. For this purpose, subscriber information stored in the HSS 114 may be used .

Here, the HSS (Home Subscriber Server) 114 may refer to a subscriber information management node including a database storing subscriber information based on IMS based on a communication network, and may include subscriber profile information, authentication, Related data and the like can be provided.

Next, the TAS (Telephony Application Server) 116 may refer to an application service node. For example, the TAS (Application Telephony Application Server) 116 may include an application service node such as smart call forwarding, caller display, Change of message fields for management and call processing, and the like.

Also, the TAS 116 transmits an internal DB (not shown) when a call request is attempted from another correspondent terminal (e.g., counterpart terminal B) while the NON-USIM terminal and the counterpart terminal (e.g., counterpart terminal A) It is checked whether the called party is the smart call forwarding subscriber and whether the call is currently in the busy state and the subscriber who is subscribed to the standby service during the call. If it is determined that the subscriber is a smart call forwarding subscriber and the call waiting subscriber is subscribed to the service And a function of processing a call incoming to the smart call diverting number for a new call request from another counterpart terminal.

For example, when the TAS 116 attempts to make a call from the counterpart terminal B, the TAS 116 changes the SMS number for the smart call forwarding application to the called number, generates a SIP INVITE message, and then transmits the CSCF 112 To the NAG 108, and the like.

Then, the TAS 116 provides a function of performing signaling for call waiting processing by transmitting a re-INVITE message to a counterpart terminal (for example, the counterpart terminal A) Thereby enabling the call path between the NAG 108 and the counterpart terminal, which is currently in the call in progress, to be in a hold state (standby state).

Next, when a call request is received from another counterpart terminal during a call between the NON-USIM terminal and the counterpart terminal according to the present embodiment having the above-described configuration, a series of processes Will be described.

FIG. 2 is a flowchart illustrating a main procedure for converting a call between a NON-USIM terminal and a counterpart terminal into an idle call according to the present invention.

First, in order to enhance convenience and understanding of the explanation, the IP terminal 102, which is a NON-USIM terminal, uses the telephone line provided through the smart call diversion application 1064 mounted on the communication terminal 106 as the USIM terminal When a new call (new call) is received from the counterpart terminal B 122 while the counterpart terminal A 120 is in the middle of a call, a call with the counterpart terminal A is switched to the idle mode, Is accepted.

Referring to FIG. 2, since a communication channel is established between the IP terminal 102 and the counterpart terminal A 120, the smart call diversion application 1022 and the USIM terminal 102, which are mounted in the IP terminal 102 as the NON- Each of the smart call forwarding applications 1064 installed in the communication terminal 106 is activated according to a push message provided from the push server 110 and is connected to the NAG 108 and the notification channel.

First, when the IP terminal 102 is connected to the third party terminal B 122 in a state where the IP terminal 102 is in communication with the counterpart terminal A 120 via the smart call forwarding application 1064 of the communication terminal 106, (IP terminal 102), the corresponding signaling is routed to the TAS 116 in the IMS network A (S202).

Next, the TAS 116 searches the internal DB to determine whether the called party is a smart call forwarding subscriber and is currently in a busy state and a subscriber who is subscribed to a standby service in the call. Through this confirmation, the smart forwarding subscriber The mobile terminal B 122 prepares the incoming call to the smart call diverting number for the new call request.

In this case, in the case of a general smart call forwarding call, both the parent number and the child number are attempted to be called. In this case, however, the call is handled only by the child number since the child terminal is in a conversation with the partner terminal A (120) with the current child number.

That is, the TAS 116 changes the mobile number for smart call forwarding to the called number, generates a SIP INVITE message, and transmits the SIP INVITE message to the NAG 108 via the CSCF 112 S204).

Next, the NAG 108 searches for the user ID and the device ID associated with the corresponding user number through inquiry of the internal DB, generates a Telco Call Notification message, To the smart call forwarding application 1064 installed in the mobile phone 106 (S206). At this time, the telco call reception notification message may include call related information included in the call connection request (INVITE).

In response, the smart call forwarding application 1064 transmits a relay call (Relay Call) in order to deliver an incoming call from the counterpart terminal B 122 to the NON-USIM terminal (i.e., the IP terminal 102) API message to the NAG 108 (S208). Here, the relay call origination API message may include, for example, a user ID, a device ID, telco information (calling number, called number, outgoing lettering, NON-USIM terminal information,

The NAG 108 transmits a Relay Call Notification message to the NON-USIM terminal corresponding to the device ID, that is, the smart call forwarding application 1022 of the IP terminal 102 (S210 ).

As a result, the IP terminal 102 displays on the UI an indication that a new call has arrived to the user, and provides a menu function to indicate whether or not to accept the new call. The user can accept the new call You can choose whether or not.

When the user selects a menu for accepting a new call in the above-described situation, a call processing procedure for starting the currently busy call to a standby state is started. To this end, the smart call forwarding application 1022 of the IP terminal 102 transmits, Call control API message to the NAG 108 (S212). The telco call control forwarding API message may include, for example, "hold" request information requesting to perform a call waiting function have.

In response to this, the NAG 108 generates a telco control delivery notification message corresponding to the received telco call control delivery API and transfers it to the smart call forwarding application 1064 of the communication terminal 106 (S214) . Here, the " hold "request information is included in the telco call control delivery notification message.

Next, the smart call forwarding application 1064 transmits a telco call hold API message corresponding to the received telco call control delivery notification message, that is, a call in progress between the user of the IP terminal 102 and the user of the counterpart terminal A 120 (I.e., a standby request message) to the NAG 108 (S216).

Then, the NAG 108 generates a re-INVITE message (including SDP (Session Description Protocol) information) for waiting for an existing call between the IP terminal 102 and the counterpart terminal A 120 CSCF 112 to the TAS 116 (S218).

In response to this, the TAS 116 performs signaling for call waiting processing by transmitting a re-INVITE message to the counterpart terminal A 120, and as a result, the counterpart terminal A 120 and the NAG The call path between the base station 108 and the base station 108 is switched to a hold state (standby state) (S222).

On the other hand, when the user of the IP terminal 102 accepts a new call (incoming call from the counterpart terminal B), the smart call forwarding application 1022 of the IP terminal 102 transmits a telco call control Following the transfer API message, a Relay Call Accept API message for accepting the new call is called and transferred to the NAG 108 (S224).

The NAG 108 generates a relay call admission notification message corresponding to the relay call admission API message and transmits the message to the smart call forwarding application 1064 of the communication terminal 106 (S226) Let it know that it is a response situation.

Then, the smart call forwarding application 1064 of the communication terminal 106 calls the telco acceptance API message and transfers it to the NAG 108 (S228). Here, the telco call admission API message may provide a function of accepting a call of a telco at the USIM terminal.

In response to this, the NAG 108 makes a call to the new call based on the API messages sent between the smart call forwarding application 1064 of the communication terminal 106 and the smart call forwarding application 1022 of the IP terminal 102 The IP terminal 102 establishes a call path through the NAG 108 when the IP terminal 102 is in an NAT environment and sets up a call path when the IP terminal 102 is in an environment where there is no NAT. And the communication terminal 106, that is, the smart call forwarding application 1022 and the smart call forwarding application 1064 via P2P.

That is, the NAG 108 generates a 200 OK response message for the initial call connection request (INVITE), and then transmits the 200 OK response message to the TAS 116 via the CSCF 112. Through this, the IP terminal 102 and the counterpart terminal B (122).

The TAS 116 sends a 200 OK message to the counterpart terminal B 122 in response to the call connection request to process the signaling for the new call setup.

As a result, a call setup and a media bearer are finally established between the correspondent terminal B 122 and the NAG 108. In the NAG 108, the media to be communicated with the communication terminal 106, Connect with the bearer.

That is, in the NAG 108, the NON-USIM terminal ?? NAG ?? USIM terminal - the first call to NAG and NAG ?? Sets up a second call path to be connected between the counterpart terminals B and then connects the first call path and the second call path to each other and connects the incoming call from the counterpart terminal B 102 to the corresponding IP terminal 102, At this time, the counterpart terminal A 120 maintains a call waiting state (standby state).

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. It is easy to see that this is possible. That is, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention but to limit the scope of the present invention.

Therefore, the scope of protection of the present invention should be construed in accordance with the following claims, and all technical ideas within the scope of equivalents should be interpreted as being included in the scope of the present invention.

According to the embodiment of the present invention, when a new call is received from a counterpart terminal B while the NON-USIM terminal is in communication with the counterpart terminal A using the call path via the USIM terminal, It is possible to provide a call transfer method and a communication terminal for the call transfer service.

The present invention including such a technical configuration is characterized in that when a new call is received from the counterpart terminal B while the NON-USIM terminal is in communication with the counterpart terminal A using the call path via the USIM terminal, USIM terminal and the counterpart terminal B by making a call connection between the NON-USIM terminal and the counterpart terminal B, it is possible to effectively satisfy various service needs of the terminal users related to the call waiting call transfer service for the NON-USIM terminal.

102 and 104: IP terminal
106: communication terminal
108: NAG
110: push server
112: CSCF
114: HSS
116: TAS
118: Network
120: Relative terminal A
122: Relative terminal B
1022, 1042, 1064: Smart forwarding app

Claims (4)

A method for switching between calls,
Receiving a call connection request from a second terminal to the NON-USIM terminal while a call is connected between the NON-USIM terminal and the first terminal through a call path via the USIM terminal;
Switching a call connected between the NON-USIM terminal and the first terminal to an idle call by a network API gateway (NAG)
Wherein the NAG establishes a first call path between the NON-USIM terminal and the USIM terminal and sets a second call path between the USIM terminal and the second terminal by the NAG, Connecting a call between terminals
The method comprising the steps of:
The method according to claim 1,
The step of switching to the waiting call comprises:
Notifying, by the NAG, the call connection request to the NON-USIM terminal via the USIM terminal;
Generating a standby request by the NAG to wait for a call connected between the NON-USIM terminal and the first terminal through communication with the USIM terminal;
Switching a call connected between the NON-USIM terminal and the first terminal to an idle call by performing signaling with an IMS (IP Multimedia Subsystem) network based on the generated wait request by the NAG;
The method comprising the steps of:
A communication terminal for switching a call connected between a NON-USIM terminal and a first terminal to a stand-by call,
USIM terminal when receiving a call connection request from the second terminal to the NON-USIM terminal while a call is connected between the NON-USIM terminal and the first terminal through the communication path via the communication terminal, And a call switching unit for making a call connected between the second terminal and the second terminal,
Wherein the call terminating unit is configured to switch a call connected between the NON-USIM terminal and the first terminal to an idle call and to make a call between the NON-USIM terminal and the USIM terminal and a call between the USIM terminal and the second terminal, USIM terminal and the second terminal by establishing a second call channel
Communication terminal.
The method of claim 3,
Wherein the call-
And providing an interface capable of turning on / off the function of switching the first terminal to the standby call
Communication terminal.

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