JP2020031450A - Communication system, communication method, and program - Google Patents

Abstract

To provide a technique capable of improving convenience when a mobile phone is used as an extension phone.SOLUTION: In a communication system having a terminal and a management device, the management device includes storage means for storing information in which external numbers and extension numbers of one or more terminals are associated with each other, and notifying means for acquiring the extension numbers from the information and notifying the terminal of the extension numbers when a notification of the extension number corresponding to an external number of the destination is requested from the terminal, and the terminal includes request means for requesting a notification of an extension number corresponding to an external number of the destination received from a user, and communication means for making a call using the extension number notified from the management device.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a communication system, a communication method, and a program.

  In general, companies have built their own extension systems having a plurality of telephones with extension numbers. In addition, in the extension system, a telephone call to an outside line number contracted for each base or organization can be answered by one of the telephones.

  Also, in recent years, mobile communication operators have provided extension services that allow a mobile phone to be used as a part of a telephone in an extension system in a company. By using the extension service, users in the company can easily reach other users regardless of their location by simply calling the extension number of another user. Thus, the operational efficiency can be improved.

JP 2013-229747 A

  In the above-described extension service, various functions related to extension calls are provided. As an example, a function to talk using an extension number between mobile phones subscribed to the extension service, a function to answer a held call addressed to an outside line number with a mobile phone subscribed to the extension service, etc. is there.

  Various functions provided by the extension service are basically controlled based on the calling number when calling from a mobile phone. For example, when making a call between mobile phones subscribed to this extension service, if the call is made with an extension number, it is treated as an extension call, and if the call is made with an external number, it is not an extension but a regular mobile phone Is treated as a call. Also, for example, when using the function of answering a held call received to an external line number with a mobile phone, a call is made from the mobile phone to a special number assigned in advance for each external line number, so that the external line number is addressed. Can be answered on a mobile phone.

  However, when a mobile phone is used as an extension phone, it is necessary for the user to know in advance various numbers (such as the extension number and special number of the other party) for using the functions provided by the extension service. there were. In addition, the user has to dial various numbers, for example, and it takes time to respond to a held call.

  The present invention has been made in view of the above, and an object of the present invention is to provide a technique capable of improving convenience when using a mobile phone as an extension phone.

  A communication system according to an embodiment of the present invention is a communication system having a terminal and a management device, wherein the management device stores information in which an external number and an extension number of one or more terminals are associated with each other. A storage unit, and a notifying unit that obtains an extension number from the information and notifies the terminal when the notification of the extension number corresponding to the extension number of the call destination is requested from the terminal, Has a requesting means for requesting notification of an extension number corresponding to an external number of a destination received from a user, and a communication means for making a call using the extension number notified from the management device.

  According to the embodiments of the present invention, there is provided a technology capable of improving convenience when a mobile phone is used as an extension phone.

FIG. 1 is a diagram illustrating a configuration example of a communication system according to a first embodiment. FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal and a management device according to the first embodiment. It is a figure showing an example of a telephone directory. FIG. 5 is a sequence diagram illustrating an operation example of the communication system according to the first embodiment. It is a figure showing the example of a display of a pick-up button. FIG. 13 is a sequence diagram illustrating an operation example of the communication system according to the second embodiment. FIG. 14 is a diagram illustrating an example of a functional configuration of a management device and a PBX according to a third embodiment. It is a figure showing an example of prefix information. FIG. 14 is a sequence diagram illustrating an operation example of a communication system according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments. Although the following embodiments are based on a communication system used in a company, the embodiments of the present invention can be applied to a communication system used in any organization regardless of the company. It is possible.

[First embodiment]
<System configuration>
FIG. 1 is a diagram illustrating a configuration example of a communication system according to the first embodiment. The communication system includes a terminal 10, a management device 20, a private branch exchange (PBX) 30, and a fixed telephone 40. In the example of FIG. 1, only one terminal 10 is illustrated, but for convenience, a plurality of terminals 10 may be provided. The terminal 10, the management device 20, and the PBX 30 are connected to a PLMN (Public Land Mobile Network) provided by a mobile communication operator.

  The PBX 30 and the fixed telephone 40 are intended to be exchanges and telephones used in an extension system (hereinafter simply referred to as “extension system”) independently constructed in a company. FIG. 1 shows one PBX 30 and one fixed telephone 40, but for convenience, a plurality may be provided. For example, in the communication system according to the first embodiment, the PBX 30 may be installed so that one PBX 30 covers all the bases and organizations, or the PBX 30 may be provided for each base or organization in a company. It may be installed.

  In the first embodiment, a mobile communication operator providing a PLMN provides an extension service (hereinafter, simply referred to as "extension service") in which a mobile phone can be used as a part of a telephone in an extension system. It is assumed that That is, it is assumed that the PLMN shown in FIG. 1 has an extension service providing device (switch, server, etc.) for providing an extension service.

  The terminal 10 has a function of making a call via the PLMN. The terminal 10 is, for example, a mobile phone, a tablet terminal, a smartphone, or the like. However, any terminal having a function of making a call via the PLMN (for example, a PC having a built-in or external communication unit ( Personal Computer). It is assumed that the terminal 10 can use the extension service (the extension service has been contracted) and the terminal 10 is assigned a unique extension number.

  The management device 20 has a function of providing various numbers for using a function provided by the extension service in response to a request from the terminal 10. The management device 20 can communicate with the terminal 10 mutually. The management device 20 may communicate with the terminal 10 via the PLMN, or may communicate with the terminal 10 via another network such as a wireless LAN instead of the PLMN. . The management device 20 may be, for example, a general computer such as a PC or a server.

  The PBX 30 is an exchange used in the extension system, and has various functions for realizing an extension call performed between the fixed telephones 40 connected to the PBX 30. The PBX 30 is connected to a PSTN (Public Switched Telephone Network), and has a function of transmitting and receiving an external line using an external line number assigned according to a contract with a fixed communication operator that provides the PSTN. are doing. Further, the PBX 30 is connected to an extension service providing device of the PLMN, and has a function of realizing an extension call between the terminal 10 and the fixed telephone 40, a function of realizing an outgoing call from the terminal 10 via the PBX 30 and the like. are doing. The PBX 30 may be a PBX uniquely installed by a company, a PBX lent by a mobile communication operator as part of an extension service, or a virtual PBX on a cloud. It may be.

  The fixed telephone 40 is a telephone used in the extension system. The fixed telephone 40 is not limited to a fixed telephone, but may be a wirelessly movable telephone. The fixed telephone 40 is assigned an extension number unique to the fixed telephone 40. The extension number unique to the fixed telephone 40 and the extension number unique to the terminal 10 described above are assigned so as not to overlap with each other. It is possible to make an extension call without paying particular attention to whether the user is using the fixed telephone 40 or the terminal 10.

<Functional configuration>
FIG. 2 is a diagram illustrating an example of a functional configuration of the terminal and the management device according to the first embodiment.

(Terminal)
As illustrated in FIG. 2A, the terminal 10 includes a communication unit 101, a UI (User Interface) unit 102, and a request unit 103. These units can be realized by a process in which one or more programs installed in the terminal 10 are executed by the CPU of the terminal 10.

  The communication unit 101 has various functions (such as a calling function and an incoming call function) for wirelessly connecting to the PLMN to perform voice communication or packet communication.

  The UI unit 102 displays various icons and information on the screen of the terminal 10 using a touch panel, a screen, operation buttons, and the like included in the terminal 10 and receives various instructions from the user.

  The request unit 103 has a function of requesting (inquiring about) various numbers for using the function provided by the extension service from the management device 20. The request unit 103 also instructs the communication unit 101 to make a call using the various numbers notified from the management device 20.

(Management device)
As illustrated in FIG. 2B, the management device 20 includes a notification unit 201 and a storage unit 202. These units can be realized by a process in which one or more programs installed in the management device 20 cause the CPU of the management device 20 to execute. The notification unit 201 and the storage unit 202 may be realized using different computers, or the computers may be distributed in smaller units. That is, the management device 20 may be realized using one or a plurality of computers. Further, the one or more computers may be virtual servers using virtualization technology, or may be virtual servers implemented on a cloud.

  When receiving a request (inquiry) from the terminal 10, the notification unit 201 refers to the telephone directory stored in the storage unit 202 and stores various numbers for using the functions provided by the extension service. 10 has the function of notifying.

  The storage unit 202 stores a telephone directory. The storage unit 202 can be realized using a storage device (memory, HDD, or the like) included in the management device 20, a storage device that can be connected to the management device 20 via a network, or the like.

  FIG. 3 is a diagram illustrating an example of a telephone directory. As shown in FIG. 3, the telephone directory stored in the storage unit 202 stores a telephone directory for each individual and a telephone directory for each organization. “Name” indicates an individual name or an organization name. “Type” indicates whether each record in the telephone directory is a personal telephone directory or an organization telephone directory.

  The “pickup special number” is a special number that is assigned in advance for each outside line number by a mobile communication operator providing an extension service and is used when picking up (answering a held call) a held call (an incoming call on hold). . In other words, the pick-up special number is not a number managed by a company constructing the extension system (it is uniquely determined), but a number managed by the extension service provided by the mobile communication operator. Note that the special number means a special number different from a normal telephone number (for example, a telephone number starting from 0).

  The example in FIG. 3 shows that the user can respond to a held call on the outside line number (0451111111) of the organization X by dialing the special number (2001) from the terminal 10. Similarly, by dialing the special number (2002) from the terminal 10, the user can respond to the held call to the outside line number (0452222222) of the organization Y.

  The “outside line number” is a telephone number assigned according to a contract with a mobile communication operator or a fixed communication operator. In the example of FIG. 3, the external numbers of the individuals A to C are telephone numbers assigned in a contract with the mobile communication operator, and the external numbers of the organizations X to Z are the telephone numbers assigned in the contract with the fixed communication operator. Number. “Extension number” is an extension number used in the extension system. In the example of FIG. 3, the extension numbers of the individuals A to C are extension numbers assigned by the mobile communication operator, and the extension numbers of the organizations X to Z are extension numbers assigned by setting the PBX 30.

  “Affiliation” indicates which organization each individual belongs to. In the example of FIG. 3, it is shown that the individuals A to C belong to the organization X, the individuals D and E belong to the organization Y, and the individuals F and G belong to the organization Z. . The "affiliation" of each individual in the telephone directory is changed as appropriate in accordance with personnel changes and the like. For example, when the individual A is changed from the organization X to the organization Y due to a personnel change or the like, the telephone directory is updated so that the individual A belongs to the organization Y instead of the organization X.

<Operation example of communication system>
FIG. 4 is a sequence diagram illustrating an operation example of the communication system according to the first embodiment. FIG. 4 shows a case where a customer who wishes to transfer to the individual A belonging to the organization X receives a telephone call from the fixed telephone of the organization X. Assume a situation where you answer the phone. In the following description, it is assumed that the records shown in FIG. 3 are stored in the telephone directory.

  In step S101, the PBX 30 accepts a call addressed to the organization X (a call whose destination is 0451111111).

  In step S102, the PBX 30 calls the fixed telephone 40 of the organization X.

  In step S103, the user who has received the incoming call presses the hold button of the fixed telephone 40.

  In step S104, fixed telephone 40 transmits a hold instruction signal to PBX 30.

  In step S105, the PBX 30 places the call accepted in step S101 on hold.

  In step S106, the user who has received the call notifies the individual A that the customer has called the fixed telephone 40 of the organization X and is on hold.

  In step S107, the individual A presses a pickup button displayed on the screen of the terminal 10 to answer the call on hold. The UI unit 107 of the terminal 10 recognizes that the pickup button has been pressed.

  Here, a display example of the pickup button displayed on the screen of the terminal 10 will be described with reference to FIG. The example in FIG. 5A shows an example in which a pickup button is displayed in a menu displayed after the application for controlling the extension service is activated, and the example in FIG. On the top screen of FIG. 1, an example is shown in which a pickup button (pickup icon) is displayed separately from an icon for activating an application for controlling an extension service. In the example of FIG. 5B, a pickup button (pickup icon) is displayed on the top screen, so that the user can respond to the held call more quickly than in the example of FIG. 5A. Returning to FIG. 4, the description will be continued.

  In step S108, the request unit 103 of the terminal 10 transmits a pickup special number request signal to the management device 20. The special number request signal for pickup includes the extension number (61001) of the terminal 10 itself.

  In step S109, the notification unit 201 of the management device 20 acquires the pickup special number (2001) by searching the telephone directory using the extension number (61001) included in the pickup special number request signal. More specifically, the notification unit 201 identifies the user (individual A) corresponding to the extension number by searching the telephone directory using the extension number (61001) received in the processing procedure of step S108 as a key. . Next, the notification unit 201 specifies the organization (organization X) to which the specified user (individual A) belongs, and acquires the pickup special number (2001) corresponding to the specified organization.

  In step S110, the notification unit 201 of the management device 20 transmits a pickup special number response signal including the pickup special number (2001) to the terminal 10.

  In step S111, the request unit 103 of the terminal 10 instructs the communication unit 101 to make a call using the pickup special number (2001) notified from the management device 20. The communication unit 101 makes a call to the pickup special number (2001) specified by the request unit 103. Note that a control signal related to a call originated from the terminal 10 is transmitted to the PBX 30 via each device in the PLMN (base station, exchange, and extension service providing device provided in the PLMN). This means that the pickup special number is a special number assigned by the mobile communication operator, and that each device in the PLMN recognizes that a control signal relating to a call originated by the special number should be transferred to the PBX 30. This is because it can be done.

  In step S112, the PBX 30 releases the hold of the call received in step S101, and connects the line related to the call whose hold has been released to the extension service providing apparatus. The line is connected to the terminal 10 via each device in the PLMN, and a call is started between the terminal 10 and the customer's telephone.

  The operation example of the communication system according to the first embodiment has been described above. According to the first embodiment, the pickup special number for responding to the held call is notified from the management device 20 to the terminal 10. Therefore, when the user (individual A) answers the held call at the terminal 10, the user (person A) can answer the held call without dialing the special number for pickup. Further, when the user (individual A) answers the held call at the terminal 10, the user (individual A) can answer the held call without knowing the pickup special number. In addition, even if the organization to which the user belongs is changed due to a transfer, the user can answer a held call without knowing the pickup special number corresponding to the changed organization. Become.

[Second embodiment]
Next, a second embodiment will be described with reference to the drawings. Note that points that are not particularly mentioned may be the same as in the first embodiment.

<Operation example of communication system>
FIG. 6 is a sequence diagram illustrating an operation example of the communication system according to the second embodiment. In FIG. 6, the terminal 10 of the individual A is described as “terminal 10a”, and the terminal 10 of the individual C is described as “terminal 10c”. FIG. 6 assumes a situation in which person A makes a call from terminal A of person A to terminal 10c of person C. In addition, when making a call, the individual A dials the outside number of the terminal 10c without knowing the extension number of the terminal 10c of the individual C (or dials the outside number by mistake, knowing the extension number). Is assumed). In the following description, it is assumed that the records shown in FIG. 3 are stored in the telephone directory.

  In step S201, the UI unit 107 of the terminal 10a receives, from the individual A, selection (or input) of the external line number (090333333333) of the individual C and depression of the call button.

  In step S202, the request unit 103 of the terminal 10a transmits an extension number search request signal including the external number (090333333333) of the destination to the management device 20.

  In step S203, the notifying unit 201 of the management device 20 obtains the extension number (61003) corresponding to the external number by searching the telephone directory using the external number (090333333333) included in the extension number search request signal. I do.

  In step S204, the notification unit 201 of the management device 20 transmits an extension number search response signal including the extension number (61003) to the terminal 10. If the extension number corresponding to the external number does not exist in the telephone directory, the notification unit 201 of the management device 20 may transmit information indicating that the extension number corresponding to the external number does not exist to the terminal 10. Good.

  In step S205, the request unit 103 of the terminal 10 instructs the communication unit 101 to make a call using the extension number (61003). The communication unit 101 makes a call to the extension number (61003) specified by the request unit 103. The control signal related to the call originated from the terminal 10 is transmitted to the terminal 10c via each device (base station, exchange, and extension service providing device provided in the PLMN) in the PLMN. This is because the extension number of the terminal 10c is assigned by the mobile communication operator, and each device in the PLMN can recognize that the terminal to which the extension number is assigned is the terminal 10c.

  In step S112, a call is started between the terminal 10a and the terminal 10c.

  The example of the operation of the communication system according to the second embodiment has been described above. According to the second embodiment, the extension number of the terminal 10 is notified from the management device 20 to the terminal 10. Therefore, when calling from the terminal 10a to the terminal 10c, the user (individual A) can make an extension call to the terminal 10c without dialing the extension number of the terminal 10c. Further, the user (individual A) can make an extension call to the terminal 10c without knowing the extension number of the terminal 10c. Further, even if the user dials an outside line number by mistake, it is automatically converted to an extension number, so that it is possible to save, for example, a call charge.

[Third embodiment]
Next, a third embodiment will be described with reference to the drawings. When the PBX 30 according to the third embodiment receives a destination telephone number including a prefix corresponding to each of various functions provided in the PBX 30 itself, the PBX 30 performs the prefix in the call processing related to the call via the PBX 30. Has a function of operating a function corresponding to. Note that points which are not particularly mentioned may be the same as the first embodiment or the second embodiment.

<Functional configuration>
FIG. 7 is a diagram illustrating an example of a functional configuration of a management device and a PBX according to the third embodiment.

(Management device)
As illustrated in FIG. 7A, the management device 20 includes a notification unit 301 and a storage unit 302.

  When receiving a request (inquiry) from the terminal 10, the notifying unit 301 refers to the prefix information stored in the storage unit 202, and uses the function provided by the PBX to operate (operate). It has a function of notifying the terminal 10 of the fix. The storage unit 302 stores prefix information in addition to the telephone directory.

  FIG. 8 shows an example of the prefix information. “Function name” indicates the name of a function included in the PBX 30. “Prefix” indicates a prefix corresponding to “function name”. In the example of FIG. 8, the function A is a source number conversion function, and the prefix corresponding to the function is “8”. The calling number conversion function is intended to convert the calling telephone number (external number or extension number) to the external number of the organization to which the user corresponding to the telephone number belongs in the PBX 30. ing. The source telephone number conversion function is an example, and the third embodiment is not limited to this, and can be applied to any function of the PBX.

(PBX)
As shown in FIG. 7B, the PBX 30 includes a function execution unit 401, a storage unit 402, and a PSTN communication unit 403. Each of these units can be realized by a process that causes the CPU of the PBX 30 to execute one or more programs installed in the PBX 30.

  The function execution unit 401 executes various functions of the PBX. The function execution unit 401 has a function of referring to a telephone directory stored in the storage unit 402 as necessary.

  The storage unit 402 stores a telephone directory. The storage unit 402 can be realized using a storage device (memory, HDD, or the like) included in the PBX 30, a storage device that can be connected to the PBX 30 via a network, or the like. The telephone directory stored in the storage unit 402 is the same as the telephone directory shown in FIG. Note that the PBX 30 may not hold the storage unit 402. In this case, the function execution unit 401 may inquire the management device 20 about the contents of the telephone directory as needed.

  The PSTN communication unit 403 has various functions (such as a calling function and an incoming call function) for making a voice call by connecting to the PSTN.

<Operation example of communication system>
FIG. 9 is a sequence diagram illustrating an operation example of the communication system according to the third embodiment. FIG. 9 assumes a situation in which a call is made to a customer from the terminal 10 of the individual A using the above-mentioned source number conversion function (function A). In the following description, it is assumed that the records shown in FIG. 3 are stored in the telephone directory stored in the storage unit 302 of the management device 20 and the storage unit 402 of the PBX 30.

  In step S301, the UI unit 107 of the terminal 10a selects (or inputs) the customer's outside line number (0457777777) from the individual A, gives an instruction to use the above-mentioned caller ID conversion function (function A), and issues a call. Accepts pressing of the call button.

  In step S302, the request unit 103 of the terminal 10a transmits a prefix inquiry signal to the management device 20. The prefix inquiry signal includes the outside line number (0457777777) of the customer who is the destination and information indicating the source number conversion function (function A). The information indicating the source number conversion function (function A) may be an identifier unique to each function, or the like, and is not limited thereto, and may be any information. For example, when the prefix inquiry signal includes the extension number of the terminal 10, it may mean that the prefix inquiry signal includes information indicating the source number conversion function (function A). .

  In step S303, the notifying unit 301 of the management device 20 retrieves the prefix information (8) by searching the prefix information using the information indicating the source number conversion function (function A). .

  In step S304, the notification unit 201 of the management device 20 adds a prefix to the destination external line number included in the prefix inquiry signal. Further, the notification unit 201 transmits to the terminal 10 a prefix inquiry response signal including the outside line number (8045777777) of the destination to which the prefix is added.

  In step S305, the request unit 103 of the terminal 10 instructs the communication unit 101 to make a call using the outside line number (80474577777) of the destination to which the prefix has been added. The communication unit 101 makes a call to the outside line number (8045777777) specified by the request unit 103. The communication unit 101 includes its own extension number (61001) as the caller's telephone number in the control signal for the call. A control signal related to a call originated from the terminal 10 is transmitted to the PBX 30 via each device in the PLMN (base station, exchange, and extension service providing device provided in the PLMN).

  In step S306, the function execution unit 401 of the PBX 30 checks whether a prefix is added to the destination line number included in the received control signal. In the example of FIG. 9, the function execution unit 401 of the PBX 30 confirms that “8” is added as a prefix, and recognizes that the above-described source number conversion function (function A) needs to be operated. Will be.

  In step S307, the function execution unit 401 of the PBX 30 operates the caller number conversion function (function A). Specifically, the function execution unit 401 specifies the user (individual A) having the extension number by searching the telephone directory using the extension number (61001) of the transmission source included in the received control signal as a key. I do. Next, the function execution unit 401 specifies the organization (organization X) to which the specified user (individual A) belongs, and acquires an outside line number (0451111111) corresponding to the specified organization.

  In step S308, the PSTN communication unit 403 of the PBX 30 sets the telephone number (0457777777) excluding the prefix “8” as the destination telephone number, and sets the outside line number of the organization X (0451111111) as the source telephone number. To make a call. As a result, the telephone number of the organization X is displayed on the customer's telephone as the caller instead of the external line number of the terminal A.

  The example of the operation of the communication system according to the third embodiment has been described above. According to the third embodiment, the prefix for operating various functions of the PBX 30 is notified from the management device 20 to the terminal 10. Therefore, when using the function of the PBX 30, the user (individual A) can operate the function of the PBX 30 without giving the prefix to the telephone number of the call destination and dialing. Further, the user (individual A) can operate the functions of the PBX 30 without knowing the prefix corresponding to each of the various functions of the PBX 30.

<Supplement to the embodiment>
The embodiments can be arbitrarily combined. That is, the first embodiment and the second embodiment may be combined, the first embodiment and the third embodiment may be combined, and the second embodiment may be combined. Embodiment and the third embodiment may be combined, or the first embodiment, the second embodiment, and the third embodiment may be combined.

  The terminal 10 may include each functional unit included in the management device 20. Thereby, the terminal 10 can realize the processing according to each embodiment without accessing the management device 20.

  As described above, the functional units included in the terminal 10, the management device 20, and the PBX 30 according to each embodiment use the hardware resources such as the CPU and the memory included in the terminal 10, the processing executed by each of the management device 20 and the PBX 30. Can be realized by executing a program corresponding to. Further, the program can be stored in a storage medium.

  In each embodiment, the organization is an example of a “group”. The extension number of the terminal 10 is an example of “information for specifying the group to which the terminal belongs”. The telephone directory or prefix information is an example of “information”.

10 Terminal 20 Management device 30 PBX
101 communication unit 102 UI unit 103 request unit 201, 301 notification unit 202, 302 storage unit 401 function execution unit 402 storage unit 403 PSTN communication unit

Claims (4)

A communication system having a terminal and a management device,
The management device,
Storage means for storing information in which an external number and an extension number of one or more terminals are associated with each other;
A notification unit that obtains an extension number from the information and notifies the terminal, when a notification of an extension number corresponding to an external number of the destination is requested from the terminal,
Has,
The terminal is
Request means for requesting a notification of an extension number corresponding to an outside line number of the destination received from the user;
Communication means for making a call using the extension number notified from the management device,
A communication system comprising: The terminal and the management device are communicably connected via a public mobile phone network,
The notifying means,
When a notification of an extension number corresponding to an extension number of a call destination is requested from the terminal via the public mobile phone network, an extension number is obtained from the information and the terminal is obtained via the public mobile phone network. Notify,
The request means,
Requesting a notification of an extension number corresponding to an outside line number of the destination received from the user via the public mobile phone network,
The communication means,
The communication system according to claim 1, wherein a call is made using an extension number notified from the management device via the public mobile phone network. A communication method executed by a communication system having a terminal and a management device,
A step in which the management device stores information in which an external number and an extension number of one or more terminals are associated with each other in a storage unit;
When the management device is requested from the terminal to notify the extension number corresponding to the extension number of the destination, a step of obtaining an extension number from the information and notifying the terminal,
The terminal, requesting notification of an extension number corresponding to the outside line number of the destination received from the user,
The terminal, making a call using the extension number notified from the management device,
A communication method comprising:   A program that causes a computer to function as one of the terminals and the management device according to claim 1.

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