Patent Publication Number: US-2020304645-A1

Title: Mobile terminal, communication method, non-transitory computer-readable recording medium storing communication program, and intercom system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to and claims the benefit of Japanese Patent Application No. 2018-073985, filed on Apr. 6, 2018, Japanese Patent Application No. 2018-073991, filed on Apr. 6, 2018, Japanese Patent Application No. 2018-073998, filed on Apr. 6, 2018, and Japanese Patent Application No. 2018-079961, filed on Apr. 18, 2018, the disclosures of which including the specifications, drawings and abstracts are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a mobile terminal, an event information display method, a non-transitory computer-readable recording medium storing an event information display program, and an intercom system. 
     BACKGROUND ART 
     There has been a widely used intercom system capable of confirming a visitor to an entrance from an indoor parent device in a room via an entrance child device located in the vicinity of an entrance door. In recent years, there is a technique attracting much attention, in which a communication function is provided in an indoor parent device and confirmation of visitors is performed from a mobile terminal such as a smartphone that can be carried by a person. 
     For example, PTL 1 discloses an intercom system for connecting an entrance child device with a mobile terminal via a parent device in response to calling operation by a visitor via the entrance child device and thereafter responding to the visitor from the mobile terminal. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2011-135221 
     SUMMARY OF INVENTION 
     Technical Problem 
     Meanwhile, some of apartment buildings such as condominiums have their receptionist disposed in a lobby in the building. In such an apartment building, a visitor asks the receptionist to call a resident of a room the visitor wishes to visit. For example, the receptionist calls an indoor monitor located in the room from a telephone in the lobby to call the resident of the room and notifies the resident of the visitor. 
     The conventional system, however, has not been configured to receive an image of the visitor on a mobile terminal of the resident of the apartment building. 
     One non-limiting and exemplary embodiment of the present disclosure facilitates providing a mobile terminal and a communication method capable of receiving a call from a telephone disposed in a lobby of an apartment building and thereafter receiving an image of a visitor. 
     Solution to Problem 
     A mobile terminal according to one aspect of the present disclosure is a mobile terminal that communicates with a server that performs call control between an intercom disposed in a lobby of an apartment building and an indoor monitor, the server storing event information transmitted from the intercom, the indoor monitor, or a terminal apparatus which is connected to the server, the mobile terminal including: a receiver that receives the event information from the server; and a display section that displays the event information in chronological order from an upper side to a lower side of a display apparatus and that scroll-displays the event information. 
     An event information display method according to one aspect of the present disclosure is an event information display method for a mobile terminal that communicates with a server that performs call control between an intercom disposed in a lobby of an apartment building and an indoor monitor, the server storing event information transmitted from the intercom, the indoor monitor, or a terminal apparatus which is connected to the server, the event information display method including: receiving the event information from the server; and displaying the event information in chronological order from an upper side to a lower side of a display apparatus and scroll-displaying the event information. 
     A non-transitory computer-readable recording medium storing an event information display program according to one aspect of the present disclosure is an event information display program for a mobile terminal that communicates with a server that performs call control between a telephone disposed in a lobby of an apartment building and an indoor monitor, the server storing event information transmitted from the intercom, the indoor monitor, or a terminal apparatus connected to the server, the program causing a computer to execute processing including: receiving the event information from the server; and displaying the event information in chronological order from an upper side to a lower side of a display apparatus and scroll-displaying the event information. 
     An intercom system according to one aspect of the present disclosure includes: a telephone disposed in a lobby of an apartment building; an indoor monitor disposed in a room of the apartment building; a server that performs call control between the telephone and the indoor monitor; and a mobile terminal that communicates with the server, the server storing event information transmitted from the intercom, the indoor monitor, or a terminal apparatus connected to the server, in which the mobile terminal includes: a receiver that receives the event information from the server; and a display section that displays the event information in chronological order from an upper side to a lower side of a display apparatus and that scroll displays the event information. 
     These general and specific aspects may be implemented by using a system, a method, an integrated circuit, a computer program, or a recording medium, or by using any combination of systems, apparatuses, methods, integrated circuits, computer programs, or recording media. 
     According to one aspect of the present disclosure, a call from a telephone disposed in a lobby of an apartment building can be handled and an image of a visitor can be received. 
     Additional benefits and advantages of an embodiment of the present disclosure will be apparent from the Description and Drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the Description and 
     Drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of an intercom system according to Embodiment 1; 
         FIG. 2  is a diagram illustrating a block configuration example of a server; 
         FIG. 3  is a diagram illustrating a block configuration example of a telephone; 
         FIG. 4  is a diagram illustrating a block configuration example of a lobby intercom; 
         FIG. 5  is a diagram illustrating a block configuration example of an indoor monitor; 
         FIG. 6  is a diagram illustrating a block configuration example of a mobile terminal; 
         FIG. 7  is a diagram illustrating an example of an intercom system; 
         FIG. 8  is a diagram illustrating a block configuration example of a controller of a server; 
         FIG. 9  is a diagram illustrating a block configuration example of a controller of a mobile terminal; 
         FIG. 10  is a sequence diagram illustrating an operation example of an intercom system; 
         FIG. 11  is a diagram illustrating an example of an intercom system according to Embodiment 2; 
         FIG. 12  is a diagram illustrating a block configuration example of a controller of a server; 
         FIG. 13  is a sequence diagram illustrating an operation example of an intercom system; 
         FIG. 14  is a diagram illustrating a method of registering a mobile terminal to an intercom system according to Embodiment 3; 
         FIG. 15  is a diagram illustrating an input example of mobile terminal registration information to a mobile terminal; 
         FIG. 16  is a diagram illustrating a block configuration example of a controller of an indoor monitor; 
         FIG. 17  is a diagram illustrating a block configuration example of a controller of a server; 
         FIG. 18  is a diagram illustrating a block configuration example of a controller of a mobile terminal; 
         FIG. 19  is a sequence diagram illustrating an example of registration operation of a mobile terminal to an intercom system; 
         FIG. 20  is a sequence diagram illustrating an operation example of video setting of lobby intercom; 
         FIG. 21  is a diagram illustrating an operation example of history management of a mobile terminal; 
         FIG. 22  is a diagram illustrating a block configuration example of a controller of a mobile terminal; 
         FIG. 23  is a sequence diagram illustrating an operation example of history management of an intercom system; 
         FIG. 24  is a sequence diagram illustrating an operation example of history management of an intercom system; and 
         FIG. 25  is a sequence diagram illustrating an operation example of history management of an intercom system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. However, excessively detailed description will be omitted in some cases. For example, detailed descriptions of well-known matters and redundant explanation on substantially an identical configuration will be omitted in some cases. This is to avoid the unnecessary redundancy of the following description and to facilitate understanding by those skilled in the art. 
     Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the claimed subject matter by these drawings or descriptions. 
     Embodiment 1 
       FIG. 1  is a diagram illustrating a configuration example of an intercom system according to Embodiment 1. The intercom system is applied to apartment building  1 , such as condominiums and apartment houses, for example. Apartment building  1  includes control room  2 , lobby  3 , room  4 , and entrance  5  of room  4 , for example. 
     In control room  2 , server  11  is disposed. There are telephone  12 , lobby intercom  13 , and camera  14 , disposed in lobby  3 . In room  4 , indoor monitors  15   a  and  15   b  are disposed. Mobile terminal  16   a  is a mobile terminal possessed by a resident of room  4 . At entrance  5  of room  4 , entrance intercom  17  is disposed. 
     Server  11  is a session initiation protocol (SIP) server, for example. Server  11  performs call control between devices (excluding camera  14 ) disposed in lobby  3  and devices (including mobile terminal  16   a ) disposed in room  4 . 
     In apartment building  1 , there is a case where a receptionist is disposed in lobby  3 . In such apartment building  1 , a visitor asks the receptionist to call a resident of room  4  the visitor wishes to visit. For example, the receptionist uses telephone  12  to call indoor monitors  15   a  and  15   b  and mobile terminal  16   a  of room  4 , and calls the resident of room  4 . Telephone  12  is a SIP phone, for example. In consideration of general cases where the receptionist and the resident of room  4  talk to each other, telephone  12  is a handset-type telephone capable of suppressing leakage of voice of the resident to the outside, rather than a speaker phone-type telephone. 
     Lobby intercom  13  includes a call function and a camera, for example. In response to an input of identification information (for example, a room number or an extension number of room  4 ) for identifying room  4 , lobby intercom  13  is capable of calling indoor monitors  15   a  and  15   b  or mobile terminal  16   a  of room  4 , for example. Subsequently, lobby intercom  13  can talk with any of indoor monitors  15   a  and  15   b  or mobile terminal  16   a  that has received the call. Moreover, lobby intercom  13  uses its own camera to capture an image of a person standing in front of lobby intercom  13 , for example, and transmits a captured image (for example, a moving image) to any of indoor monitors  15   a  and  15   b,  or mobile terminal  16   a  of room  4 . 
     Camera  14  is, for example, a monitoring camera for capturing a state in lobby  3 . Camera  14  is an Internet Protocol (IP) camera without a voice call function, for example. In response to a request from any of indoor monitors  15   a  and  15   b  or mobile terminal  16   a,  camera  14  transmits the captured image to any of indoor monitors  15   a  and  15   b  or mobile terminal  16   a.    
     Indoor monitors  15   a  and  15   b  are capable of receiving a call from telephone  12  or lobby intercom  13  disposed in lobby  3  and capable of talking with telephone  12  or lobby intercom  13 . In addition, indoor monitors  15   a  and  15   b  are capable of receiving a call from entrance intercom  17  disposed in entrance  5  and capable of talking with entrance intercom  17 . 
     Each of indoor monitors  15   a  and  15   b  has a display. The displays of indoor monitors  15   a  and  15   b  display images captured by lobby intercom  13 , images captured by camera  14 , or images captured by entrance intercom  17 . 
     For example, when indoor monitors  15   a  and  15   b  are talking with telephone  12 , images captured by camera  14  are displayed on the displays of indoor monitors  15   a  and  15   b.    
     Furthermore, when indoor monitors  15   a  and  15   b  are talking with lobby intercom  13 , images captured by the camera of lobby intercom  13  are displayed on the displays of indoor monitors  15   a  and  15   b.  The displays of indoor monitors  15   a  and  15   b  display images captured by the camera of entrance intercom  17  when indoor monitors  15   a  and  15   b  are talking with entrance intercom  17 . 
     Mobile terminal  16   a  is a mobile terminal possessed by the resident of room  4 . Mobile terminal  16   a  is a smartphone, for example. Mobile terminal  16   a  is capable of receiving a call from telephone  12 , lobby intercom  13 , or entrance intercom  17  and capable of talking with telephone  12 , lobby intercom  13 , or entrance intercom  17 , via a network including a cellular phone network and the Internet. In other words, mobile terminal  16   a  is capable of talking with telephone  12 , lobby intercom  13 , or entrance intercom  17  even when mobile terminal  16   a  is outside room  4  in addition to inside room  4 . 
     Mobile terminal  16   a  includes a display. The display of mobile terminal  16   a  displays an image captured by lobby intercom  13 , an image captured by camera  14 , or an image captured by entrance intercom  17 . 
     For example, when mobile terminal  16   a  and telephone  12  are talking with each other, an image captured by camera  14  is displayed on the display of mobile terminal  16   a.  Furthermore, when mobile terminal  16   a  and lobby intercom  13  are talking with each other, an image captured by the camera of lobby intercom  13  is displayed on the display of mobile terminal  16   a.  Furthermore, when mobile terminal  16   a  and entrance intercom  17  are talking with each other, an image captured by the camera of entrance intercom  17  is displayed on the display of mobile terminal  16   a.    
     Note that while  FIG. 1  illustrates two indoor monitors  15   a  and  15   b,  the number of monitors may be one, or three or more. 
       FIG. 2  is a diagram illustrating a block configuration example of server  11 . As illustrated in  FIG. 2 , server  11  has controller  21 , storage section  22 , and communicator  23 . 
     Controller  21  performs overall control of server  11 . Controller  21  may be constituted by a central processing unit (CPU), for example. 
     Storage section  22  stores a program used for operation of controller  21 . Storage section  22  stores data used by controller  21  to perform calculation processing and to control each of sections connected to controller  21 . Storage section  22  may be configured with a storage apparatus such as a random access memory (RAM), a read only memory (ROM), a flash memory, and a hard disk drive (HDD). 
     Communicator  23  communicates with telephone  12 , lobby intercom  13 , indoor monitors  15   a  and  15   b,  and entrance intercom  17  via a network such as a local area network (LAN) installed in apartment building  1 . Furthermore, communicator  23  communicates with mobile terminal  16   a  via a network including a cellular phone network and the Internet. 
       FIG. 3  is a diagram illustrating a block configuration example of telephone  12 . As illustrated in  FIG. 3 , telephone  12  includes controller  31 , storage section  32 , communicator  33 , voice processor  34 , and operator  35 . 
     Controller  31  performs overall control of telephone  12 . Controller  31  may be constituted by a CPU, for example. 
     Storage section  32  stores a program used for operation of controller  31 . Storage section  32  stores data used by controller  31  to perform calculation processing and to control each of sections connected to controller  31 . Storage section  32  may be configured with a storage apparatus such as a RAM, a ROM, a flash memory, and an HDD. 
     Communicator  33  communicates with server  11  via a network such as a LAN installed in apartment building  1 . 
     Voice processor  34  converts analog voice data output from a microphone (not illustrated) built in a handset of telephone  12  into digital voice data, for example, and outputs the converted data to controller  31 . Voice processor  34  converts the digital voice data output from controller  31 , into analog voice data, for example, and outputs the converted data to a speaker (not illustrated) built in the handset of telephone  12 . 
     Operator  35  receives operation of the receptionist of lobby  3 , for example. Operator  35  outputs information corresponding to the received operation to controller  31 . Operator  35  is a push button for receiving an input of a telephone number, for example. 
       FIG. 4  is a diagram illustrating a block configuration example of lobby intercom  13 . 
     As illustrated in  FIG. 4 , lobby intercom  13  includes controller  41 , storage section  42 , communicator  43 , voice processor  44 , operator  45 , and image processor  46 . 
     Controller  41  performs overall control of lobby intercom  13 . Controller  41  may be constituted by a CPU, for example. 
     Storage section  42  stores a program used for operation of controller  41 . Storage section  42  stores data used by controller  41  to perform calculation processing and to control each of sections connected to controller  41 . Storage section  42  may be configured with a storage apparatus such as a RAM, a ROM, a flash memory, and an HDD. 
     Communicator  43  communicates with server  11  and mobile terminal  16   a  via a network such as LAN installed in apartment building  1 . 
     Voice processor  44  converts analog voice data output from a microphone (not illustrated) built in lobby intercom  13  into digital voice data, for example, and outputs the converted data to controller  41 . Furthermore, voice processor  44  converts the digital voice data output from controller  41 , for example, into analog voice data and outputs the converted data to a speaker (not illustrated) built in lobby intercom  13 . 
     Operator  45  receives operation of a visitor, for example. Operator  45  outputs information corresponding to the received operation to controller  41 . Operator  45  is a push button for receiving an input of a telephone number, for example. 
     Image processor  46  converts analog video image data captured by an image sensor (not illustrated) included in lobby intercom  13  into a digital signal, for example, and outputs the converted signal to controller  41 . Image processor  46  may perform predetermined image processing such as image quality adjustment, noise cancellation, image compression processing, or the like on the analog video image signal or the digital video image data. 
       FIG. 5  is a diagram illustrating a block configuration example of indoor monitor  15   a.  As illustrated in  FIG. 5 , indoor monitor  15   a  has controller  51 , storage section  52 , communicator  53 , voice processor  54 , image processor  55 , display  56 , and operator  57 . Note that indoor monitor  15   b  also has the block configuration illustrated in  FIG. 5 , and thus, description thereof will be omitted. 
     Controller  51  performs overall control of indoor monitor  15   a.  Controller  51  may be constituted by a CPU, for example. 
     Storage section  52  stores a program used for operation of controller  51 . Storage section  52  stores data used by controller  51  to perform calculation processing and to control each of sections connected to controller  51 . Storage section  52  may be configured with a storage apparatus such as a RAM, a ROM, a flash memory, and an HDD. 
     Communicator  53  communicates with server  11  via a network such as LAN installed in apartment building  1 . Furthermore, communicator  53  communicates with camera  14  via a network such as a LAN installed in apartment building  1 . Furthermore, the communicator  53  communicates with entrance intercom  17  via a network such as a LAN installed in apartment building  1 . 
     Voice processor  54  converts analog voice data output from a microphone (not illustrated) built in indoor monitor  15   a  into digital voice data, for example, and outputs the converted data to controller  51 . Voice processor  54  converts the digital voice data output from controller  51 , into analog voice data, for example, and outputs the converted data to a speaker (not illustrated) built in indoor monitor  15   a.    
     Image processor  55  converts analog video image data captured by an image sensor (not illustrated) included in indoor monitor  15   a  into a digital signal, for example, and outputs the converted signal to controller  51 . Image processor  55  may perform predetermined image processing such as image quality adjustment, noise cancellation, and image compression processing on the analog video image signal or the digital video image data. 
     Display  56  displays a video image on the basis of the digital video image data output from controller  51 . Display  56  is a liquid crystal display, for example. 
     Operator  57  receives operation of a resident of room  4 , for example. Operator  57  outputs information corresponding to the received operation to controller  51 . Operator  57  is touch screen superimposed on display  56 , for example. Operator  57  may be a push button. 
       FIG. 6  is a diagram illustrating a block configuration example of mobile terminal  16   a.  As illustrated in  FIG. 6 , mobile terminal  16   a  includes controller  61 , storage section  62 , communicator  63 , voice processor  64 , image processor  65 , display  66 , and operator  67 . 
     Controller  61  performs overall control of mobile terminal  16   a.  Controller  61  may be constituted by a CPU, for example. 
     Storage section  62  stores a program used for operation of controller  61 . Storage section  62  stores data used by controller  61  to perform calculation processing and to control each of sections connected to controller  61 . Storage section  62  may be configured with a storage apparatus such as a RAM, a ROM, a flash memory, and an HDD. 
     Communicator  63  communicates with server  11  disposed in control room  2  of apartment building  1  via a network including a cellular phone network and the Internet, for example. Furthermore, the communicator  63  communicates with camera  14  disposed in lobby  3  via a network including a cellular phone network and the Internet, for example. 
     Voice processor  64  converts analog voice data output from a microphone (not illustrated) built in mobile terminal  16   a  into digital voice data, for example, and outputs the converted data to controller  61 . Voice processor  64  converts the digital voice data output from controller  61  into analog voice data, for example, and outputs the converted data to a speaker (not illustrated) built in mobile terminal  16   a.    
     Image processor  65  converts analog video image data captured by an image sensor (not illustrated) included in mobile terminal  16   a  into a digital signal, for example, and outputs the converted signal to controller  61 . Image processor  65  may perform predetermined image processing such as image quality adjustment, noise cancellation, and image compression processing on the analog video image signal or the digital video image data. 
     Display  66  displays a video image on the basis of the digital video image data output from controller  61 . Display  66  is a liquid crystal display, for example. 
     Operator  67  receives operation of an owner of mobile terminal  16   a,  for example. Operator  67  outputs information corresponding to the received operation to controller  61 . Operator  67  is touch screen superimposed on display  66 , for example. Operator  67  may be a push button. 
     The intercom system of  FIG. 1  arranges telephone  12  and lobby intercom  13  in lobby  3 . However, depending on the type of apartment building  1 , telephone  12  alone might be disposed in lobby  3  with no lobby intercom  13  disposed in lobby  3 , in some cases. Hereinafter, as Embodiment 1, a case where telephone  12  alone is disposed in lobby  3  with no lobby intercom  13  disposed in lobby  3  will be described. 
       FIG. 7  is a diagram illustrating an example of an intercom system. In  FIG. 7 , the same reference numerals are attached to the same components as those in  FIG. 1 .  FIG. 7  illustrates receptionist A 1  of apartment building  1 , visitor A 2  visiting the resident of room  4 , and resident A 3  of room  4  who is out of the room. Resident A 3  is assumed to be out carrying mobile terminal  16   a.    
     In the intercom system of  FIG. 7 , lobby intercom  13  equipped with a camera is not disposed in lobby  3 . Therefore, in the intercom system of  FIG. 7 , camera  14  disposed in lobby  3  is used to capture visitor A 2 . 
     Visitor A 2  tells receptionist A 1  about one&#39;s visit to resident A 3  of room  4 . Receptionist A 1  uses telephone  12  to makes a phone call to room  4 . Calling by telephone  12  is performed for indoor monitors  15   a  and  15   b  disposed in room  4  and mobile terminal  16   a  possessed by resident A 3  of room  4  via server  11 . As will be described below, calling of mobile terminal  16   a  by server  11  is performed by using push notification via a push server. 
     Here is an assumed exemplary case where resident A 3  who is out uses mobile terminal  16   a  to respond to the call from telephone  12  to indoor monitors  15   a  and  15   b  and mobile terminal  16   a.    
     Mobile terminal  16   a  accesses server  11  in response to the response operation of resident A 3 . Server  11  performs call control between mobile terminal  16   a  and telephone  12  on the basis of SIP, and establishes a session between mobile terminal  16   a  and telephone  12 . This enables talking between telephone  12  and mobile terminal  16   a.    
     Furthermore, mobile terminal  16   a  accesses camera  14  without interposing server  11  in response to the response operation of resident A 3 . Mobile terminal  16   a  establishes a session with camera  14  on the basis of Real Time Streaming Protocol (RTSP). This session enables mobile terminal  16   a  to receive from camera  14  the image captured by camera  14  and display the received image on the display. 
     That is, telephone  12  and mobile terminal  16   a  establish a session on the basis of the SIP, and talk to each other. In addition, telephone  12  and camera  14  establish a session on the basis of the RTSP, and perform transmission and reception of an image. This enables mobile terminal  16   a  to perform video calling using telephone  12  and camera  14 . 
       FIG. 8  is a diagram illustrating a block configuration example of controller  21  of server  11 . As illustrated in  FIG. 8 , controller  21  of server  11  has a call controller  21   a  and a push notifier  21   b.    
     The call controller  21   a  performs call control between telephone  12  and mobile terminal  16   a  on the basis of the SIP. Moreover, call controller  21   a  performs call control between telephone  12  and indoor monitors  15   a  and  15   b  on the basis of the SIP. 
     In a case where there is a call (INVITE) addressed to indoor monitors  15   a  and  15   b  and mobile terminal  16   a  from telephone  12 , the push notifier  21   b  makes a push notification to mobile terminal  16   a.  The push notification is made via the push server. 
       FIG. 9  is a diagram illustrating a block configuration example of controller  61  of mobile terminal  16   a.  As illustrated in  FIG. 9 , controller  61  of mobile terminal  16   a  includes push notification receiver  616   a,  telephone connector  61   b,  and camera connector  61   c.    
     The push notification receiver  61   a  receives the push notification transmitted from server  11 . After receiving the push notification, the push notification receiver  61   a  displays, on a display, information (for example, an icon) indicating that a push notification has been received, for example. Alternatively, push notification receiver  61   a  notifies the owner of mobile terminal  16   a  that the push notification has been received by voice. 
     Telephone connector  61   b  establishes a session with telephone  12  that has called mobile terminal  16   a  in accordance with the operation of the owner that has recognized the push notification. For example, when the push notification icon displayed on the display is tapped by the owner, the telephone connector  61   b  establishes a session with telephone  12 . Telephone connector  61   b  establishes a session with telephone  12  on the basis of the SIP via server  11 . 
     The camera connector  61   c  accesses camera  14  in accordance with the operation of the owner who has recognized the push notification, and receives the image captured by camera  14 . For example, when the icon of the push notification displayed on the display is tapped by the owner, camera connector  61   c  establishes a session with camera  14  and receives the image captured by camera  14 . The camera connector  61   c  receives an image from camera  14  on the basis of the RTSP. 
       FIG. 10  is a sequence diagram illustrating an operation example of the intercom system. Here, it is assumed that the receptionist in lobby  3  makes a call to the extension number of room  4  using telephone  12  in response to the request of the visitor to the resident of room  4 . When a call is made to the extension number of room  4  using telephone  12 , indoor monitors  15   a  and  15   b  and mobile terminal  16   a  are called. In other words, the extension number can also be a common identifier for calling indoor monitors  15   a  and  15   b  and mobile terminal  16   a.    
     In response to the input operation of the extension number of room  4  by the receptionist, telephone  12  transmits INVITE containing the extension number of room  4  to server  11  (step S 1 ). 
     In response to reception of INVITE transmitted in step S 1 , server  11  transmits INVITE to indoor monitors  15   a  and  15   b  (step S 2 ). Note that  FIG. 10  omits illustration of indoor monitor  15   b.    
     In response to the reception of INVITE transmitted in step S 1 , server  11  transmits a push notification (PUSH notification) to mobile terminal  16   a  (step S 3 ). 
     Indoor monitors  15   a  and  15   b  transmit  100  Trying and  180  Ringing to server  11  (step S 4 ) in response to reception of INVITE transmitted in step S 2 . 
     In response to the reception of  100  Trying and  180  Ringing transmitted in step S 4 , server  11  transmits  100  Trying and  180  Ringing to telephone  12  (step S 5 ). 
     In response to the reception of INVITE transmitted in step S 2 , indoor monitors  15   a  and  15   b  call the residents of room  4  (step S 6 ). For example, indoor monitors  15   a  and  15   b  call the resident by displaying icons on the display or voice. 
     In response to the reception of the push notification transmitted in step S 3 , mobile terminal  16   a  calls the owner of mobile terminal  16   a  (step S 7 ). For example, mobile terminal  16   a  calls the owner by icon display on the display, or by voice. 
     Hereinafter, it is assumed that mobile terminal  16   a  returned the earliest response to a call made from telephone  12  to indoor monitors  15   a  and  15   b  and mobile terminal  16   a.    
     Mobile terminal  16   a  receives operation corresponding to the call from telephone  12  by the push notification from the owner of mobile terminal  16   a  (step S 8 ). For example, a push notification icon displayed on the display is tapped on mobile terminal  16   a.    
     Note that, for security reasons, the external server (server  11 ) generally cannot access mobile terminal  16   a  such as a smartphone. Still, mobile terminal  16   a  can receive a push notification from the push server that provides the push service. Accordingly, the intercom system is configured to notify the call from telephone  12  to mobile terminal  16   a  by using the push notification and cause mobile terminal  16   a  to make access to server  11 . 
     After receiving operation (tap operation) responding to the call from telephone  12  in step S 8 , mobile terminal  16   a  transmits REGISTER to server  11  (step S 9 ). 
     In response to the reception of REGISTER transmitted in step S 9 , server  11  transmits  200  OK to mobile terminal  16   a  (step S 10 ). In response to reception of REGISTER transmitted in step S 9 , server  11  transmits INVITE to mobile terminal  16   a  (step S 11 ). 
     In response to the reception of INVITE transmitted in step S 11 , mobile terminal  16   a  transmits  200  OK to server  11  (step S 12 ). 
     In response to  200  OK received in step S 12 , server  11  transmits  200  OK to telephone  12  (step S 13 ). 
     Since mobile terminal  16   a  returned the earliest response, server  11  transmits CANCEL to indoor monitors  15   a  and  15   b  in response to the call from telephone  12  (step S 14 ). 
     After receiving  200  OK at step S 13 , telephone  12  starts a voice call with mobile terminal  16   a  (step S 15 ). That is, a session is established between telephone  12  and mobile terminal  16   a.  For example, telephone  12  and mobile terminal  16   a  perform voice call by using a Real time Transport Protocol (RTP). 
     After receiving operation (for example, tap operation) responding to the call from telephone  12  in step S 8 , mobile terminal  16   a  establishes a session with camera  14  on the basis of the RTSP as indicated by dotted line frame All in  FIG. 10 . Subsequently, mobile terminal  16   a  receives an image from camera  14 . 
     For example, mobile terminal  16   a  transmits OPTIONS to camera  14  to inquire about the types of functions possessed (step S 16 ). 
     Mobile terminal  16   a  transmits SETUP to camera  14  and performs predetermined function setting for camera  14  (step S 17 ). After transmitting SETUP in step S 17 , mobile terminal  16   a  transmits PLAY to camera  14  (step S 18 ). 
     After receiving PLAY transmitted in step S 18 , camera  14  transmits a camera video image to mobile terminal  16   a  (step S 19 ). Camera  14  transmits a camera video image to mobile terminal  16   a,  for example, by using RTP. 
     In this manner, mobile terminal  16   a  that has received the call from telephone  12  establishes a session with telephone  12  by the SIP and establishes a session with camera  14  by the RTSP. This enables mobile terminal  16   a  to talk with telephone  12  and to receive the visitor&#39;s image from camera  14 . 
     As described above, push notification receiver  61   a  of mobile terminal  16   a  receives the push notification from server  11  that has received the extension number of room  4  from telephone  12 . In a case where telephone connector  61   b  has received operation corresponding to the push notification, the telephone connector  61   b  establishes a session with telephone  12  via server  11  in accordance with the SIP. In a case where camera connector  61   c  has received operation corresponding to the push notification, camera connector  61   c  establishes a session with camera  14  disposed in lobby  3  in accordance with the RTSP. This enables mobile terminal  16   a  to talk with telephone  12  disposed in lobby  3  of apartment building  1  and to receive an image of the visitor from camera  14 . That is, mobile terminal  16   a  can now make a video calling with telephone  12 . 
     Note that while camera  14  and telephone  12  have been described as separate apparatuses, camera  14  may be a camera provided at lobby intercom  13 , and telephone  12  may be a talking function included in lobby intercom  13 . In this case, mobile terminal  16   a  can establish a session and talk with lobby intercom  13  in accordance with SIP, and can also establish a session with lobby intercom  13  in accordance with RTSP and can receive an image of the visitor. That is, mobile terminal  16   a  can make a video calling with lobby intercom  13 . 
     Embodiment 2 
     In Embodiment 2, an intercom system for calling a plurality of mobile terminals from lobby intercom  13  will be described. Hereinafter, portions different from those in Embodiment 1 will be described. 
       FIG. 11  is a diagram illustrating an example of the intercom system according to Embodiment 2. In  FIG. 11 , the same reference numerals are given to the same components as those in  FIG. 1 . Note that  FIG. 11  illustrates mobile terminal  16   b  not illustrated in  FIG. 1 . Mobile terminal  16   b  is assumed to be possessed by the resident of room  4 . Mobile terminals  16   a  and  16   b  may be located outside room  4 . 
     Server  11  stores a representative extension number for simultaneously calling indoor monitors  15   a  and  15   b  together with mobile terminals  16   a  and  16   b  and an extension number for individually calling indoor monitors  15   a  and  15   b,  in association with each other. Server  11  also stores a representative extension number for simultaneously calling indoor monitors  15   a  and  15   b  together with mobile terminals  16   a  and  16   b  and an extension number for simultaneously calling mobile terminals  16   a  and  16   b,  in association with each other. 
     For example, as illustrated in Table TB  1  of  FIG. 11 , server  11  stores a representative extension number “ 1001 ” of room  4  and individual extension numbers “ 10011 ” and “ 10012 ” of indoor monitors  15   a  and  15   b,  in association with each other. Moreover, as illustrated in Table TB  1  of  FIG. 11 , server  11  stores a representative extension number “ 1001 ” of room  4  and a shared extension number “ 10013 ” of mobile terminals  16   a  and  16   b,  in association with each other. Additionally in Table TB  1 , terminal IDs “abc” and “xyz” for push notifications having been notified (granted) from the push server are stored in association with the shared extension number of mobile terminals  16   a  and  16   b.    
     Table TB  11  may be configured in storage section  22  illustrated in  FIG. 2 . Information contained in Table TB  11  is preliminarily stored in Storage section  22 . Moreover, while Table TB  11  of  FIG. 11  stores the representative extension number of room  4  and the extension number of each of apparatuses in association with each other, Table TB  11  also stores the representative extension number and the extension number of each of apparatuses in association with each other for other rooms as well. In addition, individual extension numbers (different extension numbers) may be assigned to mobile terminals  16   a  and  16   b.  Hereinafter, the terminal ID for push notification will be referred to as a push ID in some cases. 
     An operation example of the intercom system of  FIG. 11  will be described. In order to call a resident of room  4  from lobby  3  of apartment building  1 , representative extension number “ 1001 ” of room  4  is input on lobby intercom  13  as illustrated in balloon A 21  of FIG. 
       11 . Lobby intercom  13  transmits the input representative extension number “ 1001 ” to server  11 . 
     After receiving the representative extension number “ 1001 ”, server  11  refers to Table TB  1  and obtains the individual extension number corresponding to the representative extension number “ 1001 ”. For example, server  11  obtains the extension number “ 10011 ” of indoor monitor  15   a,  the extension number “ 10012 ” of indoor monitor  15   b,  and the extension number “ 10013 ” of mobile terminals  16   a  and  16   b.  Server  11  further obtains push IDs “abc” and “xyz” for mobile terminals  16   a  and  16   b,  respectively. 
     Server  11  generates an INVITE message with the obtained extension numbers “ 10011 ” and “ 10012 ”, and calls indoor monitors  15   a  and  15   b.  In addition, server  11  performs push notification with the obtained push IDs “abc” and “xyz”, and calls mobile terminals  16   a  and  16   b.    
     In this manner, indoor monitors  15   a  and  15   b  corresponding to the extension numbers “ 10011 ” and “ 10012 ” and mobile terminals  16   a  and  16   b  corresponding to the push IDs “abc” and “xyz” are called. Note that, among the called indoor monitors  15   a  and  15   b  and mobile terminals  16   a  and  16   b,  the apparatus that returned the earliest response can talk with lobby intercom  13 . 
     The intercom system illustrated in  FIG. 11  can individually call each of indoor monitors  15   a  and  15   b  and mobile terminals  16   a  and  16   b.  In order to individually call indoor monitors  15   a  and  15   b  and mobile terminals  16   a  and  16   b,  it is sufficient to input the extension numbers assigned to indoor monitors  15   a  and  15   b  and mobile terminals  16   a  and  16   b  to lobby intercom  13  (mobile terminals  16   a  and  16   b  have shared extension number and can be called simultaneously). 
     For example, to call mobile terminals  16   a  and  16   b,  it is sufficient to input “ 10013 ” on lobby intercom  13 . After receiving “ 10013 ” from lobby intercom  13 , server  11  refers to Table TB  1  and obtains the push IDs “abc” and “xyz”. Server  11  performs push notification with the obtained push IDs “abc” and “xyz”, and calls mobile terminals  16   a  and  16   b,  respectively. 
     Note that in a case where it is assumed that  2000  representative extension numbers can be registered in Table TB 1 , for example, the intercom system illustrated in  FIG. 11  can make representative calls to the  2000  rooms. In addition, in a case where it is assumed that two indoor monitors and four mobile terminals can be linked with one representative extension number (in a case where two indoor monitors and four mobile terminals can be registered to one representative extension number), the intercom system illustrated in  FIG. 11  can individually call  12000  apparatuses. 
       FIG. 12  is a diagram illustrating a block configuration example of controller  21  of server  11 . As illustrated in  FIG. 12 , controller  21  of server  11  includes extension number receiver  71   a  and call controller  71   b.    
     The extension number receiver  71   a  receives a representative extension number or an extension number transmitted from lobby intercom  13 . 
     In a case where the extension number receiver  71   a  has received the representative extension number, the call controller  71   b  transmits INVITE based on SIP to indoor monitors  15   a  and  15   b,  and transmits a push notification to each of mobile terminals  16   a  and  16   b.  The push notification is made via the push server. 
     For example, in a case where the extension number receiver  71   a  has received the representative extension number, the call controller  71   b  obtains extension numbers of indoor monitors  15   a  and  15   b  corresponding to the representative extension numbers stored in storage section  22  and push ID of mobile terminals  16   a  and  16   b.  Subsequently, the call controller  71   b  generates INVITE containing the obtained extension numbers of indoor monitors  15   a  and  15   b,  and transmits the generated INVITE to indoor monitors  15   a  and  15   b.  In addition, the call controller  71   b  transmits the obtained push ID to the push server, and makes a push notification to mobile terminals  16   a  and  16   b  via the push server. 
     After transmitting INVITE and the push notification, the call controller  71   b  establishes a session between the apparatus that returned the earliest response among the responses to the INVITE and the push notification, and lobby intercom  13 . 
     For example, it is assumed that mobile terminal  16   a  returned the response earliest among indoor monitors  15   a  and  15   b  that received INVITE and mobile terminals  16   a  and  16   b  that received the push notification. In this case, the call controller  71   b  establishes a session between mobile terminal  16   a  that returned the earliest response and lobby intercom  13 , on the basis of the SIP. 
     When extension number receiver  71   a  has received the extension number and the extension number is a number related to indoor monitors  15   a  and  15 , call controller  71   b  generates and transmits INVITE. When extension number receiver  71   a  has received the extension number and the extension number is a number related to mobile terminals  16   a  and  16   b,  call controller  71   b  generates and transmits a push notification. 
       FIG. 13  is a sequence diagram illustrating an operation example of the intercom system. It is assumed that the visitor calls room  4  with the representative extension number “ 1001 ” by using lobby intercom  13 . In  FIG. 13 , it is assumed that there are four mobile terminals  16   a  to  16   d.  That is, it is assumed that two indoor monitors  15   a  and  15   b  and four mobile terminals  16   a  to  16   d  are linked with the representative extension number “ 1001 ”. 
     Lobby intercom  13  transmits the representative extension number “ 1001 ” received from the visitor to server  11  (step S 31 ). 
     Server  11  refers to Table TB  1  and obtains the extension number and the push ID linked with the representative extension number “ 1001 ” received in step S 31 . Server  11  transmits INVITE containing the obtained extension number to indoor monitors  15   a  and  15   b  (step S 32 ), transmits the obtained push ID to the push server, and transmits a push notification to mobile terminals  16   a  to  16   d  (steps S 33  and S 34 ). 
     In response to the reception of INVITE transmitted in step S 32 , indoor monitors  15   a  and  15   b  transmit  180  Ringing to server  11  (step S 35 ). 
     In response to reception of  180  Ringing transmitted in step S 35 , server  11  transmits  180  Ringing to lobby intercom  13  (step S 36 ). 
     In response to the reception of INVITE transmitted in step S 32 , indoor monitors  15   a  and  15   b  call the resident of room  4  (step S 37 ). For example, indoor monitors  15   a  and  15   b  call the resident by displaying icons on the display or voice. 
     In response to the reception of the push notification transmitted in steps S 33  and S 34 , mobile terminals  16   a  to  16   d  call the owner of mobile terminals  16   a  to  16   d.  For example, mobile terminals  16   a  to  16   d  call the owner by icon display or voice on the display (steps S 38  and S 39 ). 
     Hereinafter, it is assumed that mobile terminal  16   a  has responded earliest to the calls made from lobby intercom  13  to indoor monitors  15   a  and  15   b  and mobile terminals  16   a  to  16   d.    
     Mobile terminal  16   a  receives, from the owner of mobile terminal  16   a,  operation corresponding to the call from lobby intercom  13  by the push notification (step S 40 ). For example, a push notification icon displayed on the display is tapped on mobile terminal  16   a.    
     After receiving operation (tap operation) corresponding to the call from lobby intercom  13  in step S 40 , mobile terminal  16   a  transmits REGISTER to server  11  (step S 41 ). 
     In response to the reception of REGISTER transmitted in step S 41 , server  11  transmits  200  OK to mobile terminal  16   a  (step S 42 ). In response to reception of REGISTER transmitted in step S 41 , server  11  transmits INVITE to mobile terminal  16   a  (step S 43 ). 
     In response to reception of the INVITE transmitted in step S 43 , mobile terminal  16   a  transmits  200  OK to server  11  (step S 44 ). 
     In response to reception of  200  OK transmitted in step S 44 , server  11  transmits  200  OK to lobby intercom  13  (step S 45 ). 
     Server  11  does not transmit INVITE to indoor monitors  15   a  or  15   b  that did not return the earliest response, and transmits CANCEL instead (step S 46 ). The timing of transmitting CANCEL is not limited to step S 46 . The timing may be at any step on and after step S 41 . 
     It is assumed that mobile terminal  16   a  responded to the call from lobby intercom  13  in step S 40 , and thereafter mobile terminals  16   b  to  16   d  responded to the call from lobby intercom  13  (step S 47 ). For example, a push notification icon displayed on the display is tapped on mobile terminals  16   b  to  16   d.    
     After receiving operation (tap operation) corresponding to the call from lobby intercom  13  in step S 47 , mobile terminals  16   b  to  16   d  transmit REGISTER to server  11  (step S 48 ). 
     In response to the reception of REGISTER transmitted in step S 48 , server  11  transmits  200  OK to mobile terminals  16   b  to  16   d  (step S 49 ). 
     Server  11  does not transmit INVITE to mobile terminals  16   b  to  16   d  that did not return the earliest response (server  11  has transmitted INVITE, in step S 43 , to mobile terminal  16   a  that has made the earliest response). In a case where mobile terminals  16   b  to  16   d  have not received INVITE from server  11  even after the lapse of a predetermined time (for example, X seconds) after transmission of REGISTER to server  11  in step S 48 , mobile terminals  16   b  to  16   d  would display an error on the display. For example, mobile terminals  16   b  to  16   d  display on the display that another mobile terminal has responded earlier to a call from lobby intercom  13 . 
     After receiving  200  OK at step S 45 , lobby intercom  13  starts voice call with mobile terminal  16   a  (step S 50 ). That is, a session is established between lobby intercom  13  and mobile terminal  16   a.  Lobby intercom  13  and mobile terminal  16   a  perform voice call by using the Real time Transport Protocol (RTP), for example. 
     In this manner, after receiving the representative extension number from lobby intercom  13 , server  11  refers to Table TB  1 , obtains the extension numbers of indoor monitors  15   a  and  15   b  corresponding to the representative extension number, and transmits INVITE. Moreover, server  11  refers to Table TB  1 , obtains the push IDs of mobile terminals  16   a  to  16   d  corresponding to the representative extension number, and transmits a push notification. With this configuration, server  11  can call indoor monitors  15   a  and  15   b  and can call the plurality of mobile terminals  16   a  and  16   d.    
     As described above, indoor monitors  15   a  and  15   b  and mobile terminals  16   a  and  16   b  are given a shared identifier (representative extension number). Extension number receiver  71   a  of server  11  receives the representative extension number from lobby intercom  13 . In response to the reception of the representative extension number, call controller  71   b  transmits INVITE based on the SIP to indoor monitors  15   a  and  15   b,  and also transmits a push notification to each of mobile terminals  16   a  and  16   b.  Subsequently, call controller  71   b  establishes a session between the apparatus that returned the earliest response among the responses to the INVITE and the push notification, and lobby intercom  13 . This processing enables lobby intercom  13  disposed in lobby  3  of apartment building  1  to call indoor monitors  15   a  and  15   b  of room  4  and the plurality of mobile terminals  16   a  and  16   b.  Subsequently, lobby intercom  13  can talk with the apparatus that returned the earliest response. 
     Embodiment 3 
     In Embodiment 3, registration of mobile terminals to an intercom system will be described. The mobile terminal of the dweller of apartment building  1  has not been registered to the intercom system. Therefore, the mobile terminal of the dweller of apartment building  1  would not be called from telephone  12  or lobby intercom  13 . In order to allow the dweller&#39;s mobile terminal to be called from telephone  12  and lobby intercom  13 , mobile terminals need to be registered to the intercom system. Moreover, even in a case where a resident of apartment building  1  wishes to incorporate a new mobile terminal into the intercom system, the resident registers the mobile terminal to the intercom system. Embodiment 3 enables registration of the mobile terminal to the intercom system easily with ensured security. Hereinafter, portions different from Embodiments 1 and 2 will be described. 
       FIG. 14  is a diagram illustrating a method of registering a mobile terminal to an intercom system according to Embodiment 3. In  FIG. 14 , the same reference numerals are given to the same components as those in  FIG. 1 . With reference to  FIG. 14 , an example of registering mobile terminal  16   a  of a resident of room  4  to the intercom system will be described. 
     As illustrated in balloon A 31  in  FIG. 14 , SIP information and RTSP information are preliminarily stored (registered) in server  11 . For example, the SIP information and the RTSP information are stored in server  11  at installation of server  11  in control room  2 . 
     In order to register mobile terminal  16   a  to the intercom system, the resident of room  4  who owns mobile terminal  16   a  presses a setting button displayed on a display of indoor monitor  15   a,  for example. When the setting button is pressed, indoor monitor  15   a  requests server  11  to transmit SIP information. 
     Note that the SIP information includes extension number, SIP password, IP address of server  11 , and port number, given to mobile terminal  16   a.  The SIP information can also be information needed for registration of mobile terminal  16   a  to the intercom system. 
     Hereinafter, the SIP information will be referred to as mobile terminal registration information in some cases. 
     In response to the SIP information transmission request from indoor monitor  15   a,  server  11  transmits the mobile terminal registration information to indoor monitor  15   a  as illustrated in balloon A 32  in  FIG. 14 . Server  11  transmits mobile terminal registration information to indoor monitor  15   a  by Hypertext Transfer Protocol Secure (HTTPS). 
     Indoor monitor  15   a  receives the mobile terminal registration information transmitted from server  11 , and displays the received mobile terminal registration information on the display as illustrated in balloon A 33  in  FIG. 14 . As described above, the mobile terminal registration information (SIP information) includes the extension number, the SIP password, the IP address of server  11 , and the port number, given to mobile terminal  16   a.  Therefore, these pieces of information are displayed on the display of indoor monitor  15   a.    
     The resident of room  4  activates an application for intercom system registration stored in mobile terminal  16   a.  Note that mobile terminal  16   a  can download the registration application from a predetermined server. 
     The resident of room  4  inputs the mobile terminal registration information displayed on the display of indoor monitor  15   a  to mobile terminal  16   a  in accordance with an instruction of the activated registration application. For example, as illustrated in balloon A 34  of  FIG. 14 , the resident of room  4  inputs the extension number, the SIP password, the IP address of server  11 , and the port number displayed on the display of indoor monitor  15   a,  to mobile terminal  16   a.  Inputting the mobile terminal registration information enables mobile terminal  16   a  to communicate with server  11 . 
     Mobile terminal  16   a  (registration application of mobile terminal  16   a ) transmits the input mobile terminal registration information to the push server and send a request to give a push ID as illustrated in balloon A 35  in  FIG. 14 . Subsequently, mobile terminal  16   a  receives (obtains) the push ID from the push server, as indicated by balloon A 36  in  FIG. 14 . 
     After acquisition of the push ID, mobile terminal  16   a  transmits the obtained push ID to server  11  as illustrated in balloon A 37  in  FIG. 14 . Mobile terminal  16   a  transmits the push ID to server  11  by using HTTPS, for example. 
     Server  11  stores the push ID transmitted from mobile terminal  16   a  as indicated by balloon A 38  in  FIG. 14 . For example, as illustrated in Table TB  1  of  FIG. 11 , server  11  stores the push ID linked with the extension number. The extension number is a number assigned to mobile terminal  16   a  and displayed on indoor monitor  15   a.    
     After receiving the push ID from mobile terminal  16   a,  server  11  transmits the camera information (RTSP information) of camera  14  to mobile terminal  16   a  as indicated by balloon A 39  in  FIG. 14 . Server  11  transmits the camera information to mobile terminal  16   a  by using HTTPS, for example. 
     The camera information includes an RTSP ID, an RTSP password, an IP address of camera  14 , and a port number, as indicated by balloon A 40  in  FIG. 14 . Mobile terminal  16   a  can receive an image from camera  14  by receiving the camera information. The camera information can be referred to as registration information to be used by mobile terminal  16   a  to communicate with camera  14  and receive an image from camera  14 . 
       FIG. 15  is a diagram for illustrating an input example of mobile terminal registration information to mobile terminal  16   a.  In  FIG. 15 , the same reference numerals are given to the same components as those in  FIG. 14 . 
     As described with reference to  FIG. 14 , mobile terminal registration information is displayed on a display of indoor monitor  15   a.  For example, the display of indoor monitor  15   a  displays mobile terminal registration information in text as illustrated in screen A 51  in  FIG. 15 . In this case, the resident of room  4  manually inputs mobile terminal registration information displayed on screen A 51 , for example. 
     The mobile terminal registration information may be displayed on the display of indoor monitor  15   a  by using a camera-readable code. For example, on the display of indoor monitor  15   a,  mobile terminal registration information may be displayed with QR code (registered trademark of DENSO WAVE INCORPORATED) as illustrated on screen A 52  of  FIG. 15 . In this case, mobile terminal  16   a  can obtain mobile terminal registration information by capturing the QR code of the mobile terminal registration information with a camera included in the terminal. 
     As described with reference to  FIG. 14 , in the case of registering mobile terminal  16   a  to the intercom system, the resident of room  4  holding mobile terminal  16   a  presses a setting button displayed on the display of indoor monitor  15   a,  for example. When the setting button is pressed, screen A 53  is displayed on the display of indoor monitor  15   a,  for example. It is possible to register up to four mobile terminals on screen A 53 . Here, two mobile terminals have already been registered on screen A 53 . For example, smartphones of “Jeffrey” and “Brian” are already registered in the intercom system. 
     “ADD” illustrated on screen A 53  indicates that a mobile terminal can be registered to the intercom system. For example, in a case where a resident in room  4  wishes to register a new mobile terminal to the intercom system, “ADD” illustrated on screen A 53  is tapped. When “ADD” is tapped, indoor monitor  15   a  displays screen A 51  or screen A 52  on the display, for example. 
     “DEL” illustrated on screen A 53  indicates that the mobile terminal already registered in the intercom system can be deleted from the intercom system. For example, in a case where a resident in room  4  wishes to delete the mobile terminal registered in the intercom system from the intercom system, tap “DEL” illustrated on screen A 53 . When “DEL” is tapped, the push ID of the mobile terminal corresponding to “DEL” is deleted from server  11 . 
       FIG. 16  is a diagram illustrating a block configuration example of controller  51  of indoor monitor  15   a.  As illustrated in  FIG. 16 , controller  51  of indoor monitor  15   a  includes a connector  816   a,  a registration information acquirer  81   b,  and a registration information display section  81   c.    
     Connector  81   a  establishes a session with lobby intercom  13  disposed in lobby  3  via server  11 . Server  11  stores mobile terminal registration information (SIP information) for allowing mobile terminal  16   a  to talk with lobby intercom  13  (in other words, to be registered to the intercom system). 
     Registration information acquirer  81   b  obtains mobile terminal registration information (SIP information) from server  11  in accordance with the operation of the resident of room  4 . For example, in a case where a resident in room  4  wishes to register mobile terminal  16   a  to the intercom system, the resident presses a setting button displayed on the display of indoor monitor  15   a.  In response to depression of the setting button, registration information acquirer  81   b  makes an access to server  11  and request the server  11  to transmit mobile terminal registration information. 
     The registration information display section  81   c  displays, on the display, the mobile terminal registration information obtained by registration information acquirer  81   b.    
       FIG. 17  is a diagram illustrating a block configuration example of controller  21  of server  11 . As illustrated in  FIG. 17 , controller  21  of server  11  includes registration information transmitter  82   a,  push ID receiver  82   b,  push notifier  82   c,  and camera information transmitter  82   d.    
     The registration information transmitter  82   a  transmits the mobile terminal registration information to indoor monitor  15   a  in response to a transmission request of mobile terminal registration information from indoor monitor  15   a.  The mobile terminal registration information is stored in storage section  22  illustrated in  FIG. 2 , for example. 
     Note that indoor monitor  15   a  that has made a request to transmit the mobile terminal registration information displays the mobile terminal registration information transmitted from registration information transmitter  82   a,  on the display. Mobile terminal registration information displayed on the display is input to mobile terminal  16   a.  When the mobile terminal registration information is input, mobile terminal  16   a  transmits the input mobile terminal registration information to the push server, and obtains a push ID from the push server. Mobile terminal  16   a  transmits the obtained push ID to server  11 . 
     Push ID receiver  82   b  receives the push ID transmitted from mobile terminal  16   a.  Push ID receiver  82   b  stores the received push ID in storage section  22  linked with the extension number to be given to mobile terminal  16   a,  for example, as illustrated in Table TB  1  in  FIG. 11 . 
     In a case where mobile terminal  16   a  is called from lobby intercom  13 , push notifier  82   c  transmits the push ID corresponding to mobile terminal  16   a  to the push server. For example, the push notifier  82   c  obtains the push ID of mobile terminal  16   a  called by lobby intercom  13  (for example, called with the representative extension number “ 1001 ” of room  4 ) with reference to Table TB  1 , and transmits the push ID to the push server. With this processing, mobile terminal  16   a  is called from the push server with a push notification. Note that after receiving a response to the push notification (REGISTER in step S 9  of  FIG. 10  or step S 41  of  FIG. 13 , for example) from mobile terminal  16   a,  controller  21  performs call control and establishes a session between mobile terminal  16   a  and lobby intercom  13 . 
     In response to reception of the push ID by push ID receiver  82   b,  camera information transmitter  82   d  transmits to mobile terminal  16   a,  camera information (RTSP information) for allowing mobile terminal  16   a  to receive the image of camera  14  disposed in lobby  3 . Mobile terminal  16   a  having received the camera information can now access camera  14  disposed in lobby  3  by the received camera information and can receive the image captured by camera  14 . 
       FIG. 18  is a diagram illustrating a block configuration example of controller  61  of mobile terminal  16   a.  As illustrated in  FIG. 18 , controller  61  of mobile terminal  16   a  includes registration information receiver  83   a,  push ID acquirer  83   b,  push ID transmitter  83   c,  and connector  83   d.    
     The registration information receiver  83   a  receives mobile terminal registration information for enabling mobile terminal  16   a  to talk with lobby intercom  13 . Mobile terminal registration information is displayed on the display of indoor monitor  15   a.  Registration information receiver  83   a  receives (obtains) mobile terminal registration information by manual input by the owner of mobile terminal  16   a,  or receives mobile terminal registration information by the camera included in mobile terminal  16   a.    
     Push ID acquirer  83   b  transmits the mobile terminal registration information received by registration information receiver  83   a  to the push server, thereby requesting the push ID assignment and then, obtains the push ID. 
     The push ID transmitter  83   c  transmits the push ID obtained by push ID acquirer  83   b  to server  11 . The push ID transmitted to server  11  is stored in server  11  linked with the extension number assigned to mobile terminal  16   a  (extension number included in the mobile terminal registration information displayed on the display of indoor monitor  15   a ). 
     After receiving a push notification from the push server, and has received response operation to the received push notification, connector  83   d  transmits REGISTER to server  11 . After receiving INVITE for the REGISTER from server  11 , connector  83   d  establishes a session with server  11 . In a case where INVITE for REGISTER has not been received from server  11  even after a predetermined time has elapsed, connector  83   d  displays an error on the display (displaying that another apparatus has received a call from lobby intercom  13 , for example). 
       FIG. 19  is a sequence diagram illustrating an example of registration operation of mobile terminal  16   a  to the intercom system. It is assumed, for example, that the resident of room  4  presses (taps) a setting button displayed on the display of indoor monitor  15   a.  It is assumed, for example, that depression of the setting button displays screen A 53  on the display of indoor monitor  15   a.  It is assumed that the resident of room  4  has pressed “ADD” button on screen A 53 . 
     In response to depression of “ADD” button, indoor monitor  15   a  requests server  11  to give the mobile terminal registration information (step S 61 ). 
     Indoor monitor  15   a  receives  200  OK including the mobile terminal registration information from server  11  (step S 62 ). 
     Indoor monitor  15   a  displays the mobile terminal registration information received in step S 62 , on the display (step S 63 ). 
     Mobile terminal  16   a  receives input of mobile terminal registration information displayed on the display of indoor monitor  15   a  from the owner of mobile terminal  16   a  (step S 64 ). 
     After receiving the input of the mobile terminal registration information in step S 64 , mobile terminal  16   a  requests the push server to give a push ID (step S 65 ). In response to the push ID request, the push server assigns a push ID to mobile terminal  16   a  and transmits the assigned push ID to mobile terminal  16   a.    
     Mobile terminal  16   a  obtains the push ID from the push server (step S 66 ). Mobile terminal  16   a  transmits the obtained push ID to server  11  (step S 67 ). 
     After receiving the push ID transmitted in step S 67 , server  11  transmits  200  OK to mobile terminal  16   a  (step S 68 ). 
     Server  11  stores the push ID transmitted in step S 67  on Table TB  1  (step S 69 ). 
     After receiving  200  OK transmitted in step S 68 , mobile terminal  16   a  requests server  11  to give camera information of camera  14  (step S 70 ). 
     Mobile terminal  16   a  receives  200  OK including the camera information from server  11  (step S 71 ). 
     Mobile terminal  16   a  stores the camera information received in step S 71  in the storage section (step S 72 ). 
     In this manner, the information for registering mobile terminal  16   a  to the intercom system is displayed on the display of indoor monitor  15   a  and input to mobile terminal  16   a.    
     With this processing, mobile terminal  16   a  can be easily and safely added to the intercom system. 
       FIG. 20  is a sequence diagram illustrating an operation example of video setting of lobby intercom  13 . It is assumed that lobby intercom  13  has received operation for calling mobile terminal  16   a.  For example, it is assumed that lobby intercom  13  receives the extension number of mobile terminal  16   a.    
     Lobby intercom  13  transmits an INVITE to server  11  in response to reception of the operation for calling mobile terminal  16   a  (step S 81 ). 
     In response to the reception of the INVITE transmitted in step S 81 , server  11  transmits INVITE to mobile terminal  16   a  (step S 82 ). 
     In response to reception of the INVITE transmitted in step S 82 , mobile terminal  16   a  transmits  100  Trying to server  11  (step S 83 ). 
     In response to reception of  100  Trying transmitted in step S 83 , server  11  transmits  100  Trying to lobby intercom  13  (step S 84 ). 
     In response to the reception of INVITE transmitted in step S 82 , mobile terminal  16   a  transmits  180  Ringing to server  11  (step S 85 ). 
     In response to reception of  180  Ringing transmitted in step S 85 , server  11  transmits  180  Ringing to lobby intercom  13  (step S 86 ). 
     Mobile terminal  16   a  transmits  200  OK to server  11  as a response to INVITE transmitted in step S 82  (step S 87 ). The  200  OK transmitted in step S 87  includes information indicating that  200  OK is a response from a mobile terminal (smartphone, for example). 
     In response to reception of  200  OK transmitted in step S 87 , server  11  transmits  200  OK to lobby intercom  13  (step S 88 ). The  200  OK transmitted in step S 88  includes information indicating that  200  OK is a response from a mobile terminal (smartphone, for example). 
     In response to the  200  OK received in step S 88 , lobby intercom  13  transmits an image to mobile terminal  16   a  (step S 89 ). At this time, on the basis of the information included in the  200  OK transmitted in step S 88  indicating that the  200  OK is a response from the mobile terminal, lobby intercom  13  selects video setting for mobile terminal  16   a  of lobby intercom  13  and transmits an image captured by camera  14 . 
     In this manner, lobby intercom  13  can transmit an image corresponding to the function of mobile terminal  16   a  that is to be called. 
     Note that while an operation example of video setting of lobby intercom  13  has been described with reference to  FIG. 20 , description can be similarly applied to entrance intercom  17 . 
     As described above, connector  81   a  of indoor monitor  15   a  establishes a session with lobby intercom  13  disposed in lobby  3  of apartment building  1  via server  11 . Server  11  stores mobile terminal registration information for enabling mobile terminal  16   a  to talk with lobby intercom  13 . Registration information acquirer  81   b  obtains mobile terminal registration information from server  11  in response to operation of the resident of room  4 . Registration information display section  81   c  displays mobile terminal registration information on the display. With this processing, it is possible to easily and safely add new mobile terminal  16   a  to the intercom system. 
     Furthermore, storage section  22  of server  11  stores mobile terminal registration information for enabling mobile terminal  16   a  to talk with lobby intercom  13 . In response to a request from indoor monitor  15   a,  registration information transmitter  82   a  transmits mobile terminal registration information stored in storage section  22  to indoor monitor  15   a.  With this processing, it is possible to easily and safely add new mobile terminal  16   a  to the intercom system. 
     In addition, indoor monitor  15   a  receives mobile terminal registration information for allowing mobile terminal  16   a  to talk with lobby intercom  13  from server  11  and displays the information on the display. Registration information receiver  83   a  of mobile terminal  16   a  receives the mobile terminal registration information displayed on the display of indoor monitor  15   a.  Push ID acquirer  83   b  transmits the mobile terminal registration information received by registration information receiver  83   a  to the push server, and thereby obtains the push ID. The push ID transmitter  83   c  transmits the push ID obtained by the push ID acquirer  83   b  to server  11 . With this processing, it is possible to easily and safely add new mobile terminal  16   a  to the intercom system. 
     Embodiment 4 
     In Embodiment 4, history management of information related to the intercom system on mobile terminals  16   a  and  16   b  will be described. Mobile terminals  16   a  and  16   b  scroll-display an incoming call history from the intercom system, images transmitted from the intercom system, or the like, in chronological order on the display. This enables the resident of room  4  to view past information related to the intercom system by using mobile terminals  16   a  and  16   b.  Hereinafter, portions different from Embodiments 1 to 3 will be described. 
       FIG. 21  is a diagram illustrating an operation example of history management of mobile terminal  16   a.  History management screen  91  in  FIG. 21  illustrates an example of a history management screen displayed on a display of mobile terminal  16   a.  History management screen  91  is displayed in response to the tapping on a history management application icon displayed on a standby screen of mobile terminal  16   a,  for example. 
     History management screen  91  displays still image  91   a  captured by lobby intercom  13 , for example. History management screen  91  further displays shooting date and time  91   b  at which lobby intercom  13  captured still image  91   a.  Still image  91   a  is an image file and can be enlarged and reduced by pinch-zoom-in operation and pinch-zoom-out operation, respectively. 
     History management screen  91  displays moving image  91   c  captured by lobby intercom  13 , for example. History management screen  91  further displays shooting date and time  91   d  at which lobby intercom  13  captured moving image  91   c.  The owner of mobile terminal  16   a  can use tap operation to perform operation such as playing, pausing, or returning to the top regarding moving image  91   c.    
     History management screen  91  displays alarm information  91   e  notified from indoor monitor  15   a,  for example. History management screen  91  further displays reception date/time  91   f  at which indoor monitor  15   a  received alarm information  91   e.    
     Note that indoor monitor  15   a  is connected to an apparatus such as a fire alarm or an emergency button apparatus, for example. When indoor monitor  15   a  receives an abnormality signal from these apparatuses, indoor monitor  15   a  transmits abnormality information to mobile terminal  16   a.  Mobile terminal  16   a  displays alarm information  91   e  on the basis of the information transmitted from indoor monitor  15   a.    
     History management screen  91  displays message  91   g  from a manager of apartment building  1 , for example. History management screen  91  further display reception date/time  91   h  of reception of message  91   g,  for example. Message  91   g  is an image file and can be enlarged and reduced by the same operation applied to still image  91   a.    
     Mobile terminal  16   a  displays the information (still image, moving image, alarm information, message, etc.) displayed on history management screen  91 , in chronological order. For example, in a case where mobile terminal  16   a  receives the latest information, mobile terminal  16   a  displays the information in addition to the bottom of history management screen  91 . In the example of  FIG. 21 , message  91   g  is the latest information. 
     Furthermore, mobile terminal  16   a  scroll-displays the information displayed on history management screen  91 . This display enables the owner of mobile terminal  16   a  to also view past information. For example, the owner of mobile terminal  16   a  can view past information by flicking down the display. 
       FIG. 22  is a diagram illustrating a block configuration example of controller  61  of mobile terminal  16   a.  Mobile terminal  16   a  includes push notification receiver  101   a,  information acquirer  101   b,  and display section  101   c.    
     The push notification receiver  101   a  receives a push notification from the push server. 
     Information acquirer  101   b  accesses server  11  in response to reception of the push notification by push notification receiver  1016   a,  and obtains information related to the history of intercom system from server  11 . The obtained information is stored in storage section  62 . Furthermore, information acquirer  101   b  receives moving images of lobby intercom  13 , camera  14 , or entrance intercom  17  captured during a call, and stores the moving images in storage section  62 . 
     Display section  101   c  displays information related to the history of the intercom system on a display. For example, display section  101   c  displays information related to the history of the intercom system on the display in scroll-display in chronological order. 
       FIG. 23  is a sequence diagram illustrating an operation example of history management of the intercom system. History management of a still image (photographic image) will be described with reference to  FIG. 23 . It is assumed that lobby intercom  13  has received an extension number of mobile terminal  16   a  from a visitor, for example. 
     In response to reception of the extension number of mobile terminal  16   a,  lobby intercom  13  images the visitor with camera  14  included in the lobby intercom  13  (step S 101 ). 
     Lobby intercom  13  transmits the photographic image captured in step S 101  to server  11  (step S 102 ). 
     In response to the reception of the image transmitted in step S 102 , server  11  transmits  200  OK to lobby intercom  13  (step S 103 ). 
     Server  11  stores the image transmitted in step S 102  (step S 104 ). 
     Lobby intercom  13  transmits INVITE to server  11  (step S 105 ). 
     In response to the reception of INVITE transmitted in step S 105 , server  11  transmits a push notification to mobile terminal  16   a  (step S 106 ). 
     In response to reception of the push notification transmitted in step S 106 , mobile terminal  16   a  attempts to obtain the image stored in server  11  (image transmission request) (step S 107 ). 
     In response to the image transmission request from mobile terminal  16   a  in step S 107 , server  11  transmits  200  OK including an image (step S 108 ). Mobile terminal  16   a  stores the image transmitted from server  11  in the storage section. 
     Mobile terminal  16   a  receives operation corresponding to the call from lobby intercom  13  using the push notification, from the owner of mobile terminal  16   a  (step S 109 ). For example, a push notification icon displayed on the display is tapped on mobile terminal  16   a.    
     After receiving operation (tap operation) corresponding to the call from lobby intercom  13  in step S 109 , mobile terminal  16   a  transmits REGISTER to server  11  (step S 110 ). 
     In response to the reception of REGISTER transmitted in step S 110 , server  11  transmits  200  OK to mobile terminal  16   a  (step S 111 ). In response to reception of REGISTER transmitted in step S 110 , server  11  transmits INVITE to mobile terminal  16   a  (step S 112 ). 
     In response to reception of the INVITE transmitted in step S 112 , mobile terminal  16   a  transmits  100  Trying to server  11  (step S 113 ). 
     In response to reception of  100  Trying transmitted in step S 113 , server  11  transmits  100  Trying to lobby intercom  13  (step S 114 ). 
     In response to the reception of INVITE transmitted in step S 112 , mobile terminal  16   a  transmits  180  Ringing to server  11  (step S 115 ). 
     In response to reception of  180  Ringing transmitted in step S 115 , server  11  transmits  180  Ringing to lobby intercom  13  (step S 116 ). 
     In response to reception of the INVITE transmitted in step S 112 , mobile terminal  16   a  transmits  200  OK to server  11  (step S 117 ). The  200  OK transmitted in step S 117  includes information indicating that  200  OK is a response from a mobile terminal (smartphone, for example). 
     In response to reception of  200  OK transmitted in step S 117 , server  11  transmits  200  OK to lobby intercom  13  (step S 118 ). The  200  OK transmitted in step S 118  includes information indicating that  200  OK is a response from a mobile terminal (smartphone, for example). 
     In response to the  200  OK received in step S 118 , lobby intercom  13  transmits an image (moving image) to mobile terminal  16   a  (step S 119 ). At this time, on the basis of the information included in the  200  OK transmitted in step S 118  indicating that the  200  OK is a response from the mobile terminal, lobby intercom  13  selects video setting for mobile terminal  16   a  and transmits an image captured by the camera. 
     Before the response to the push notification (step S 109 ), mobile terminal  16   a  requests an image (photographic image) from server  11  (step S 108 ). Subsequently, mobile terminal  16   a  stores the image in the storage section. When the history management application is activated, mobile terminal  16   a  displays the stored image as still image  91   a  illustrated in  FIG. 21 , for example. This enables the owner of mobile terminal  16   a  to confirm that there was an incoming call with an image by activating the history management application later even if it is difficult to respond to the incoming call from lobby intercom  13 . 
     In addition, mobile terminal  16   a  stores the moving image during the call transmitted in step S 119  in the storage section. When the history management application is activated, mobile terminal  16   a  displays the stored moving image as moving image  91   c  illustrated in  FIG. 21 , for example. 
     Note that while an operation example of video setting of lobby intercom  13  has been described with reference to  FIG. 20 , description can be similarly applied to camera  14  and entrance intercom  17 . 
       FIG. 24  is a sequence diagram illustrating an operation example of history management of the intercom system. With reference to  FIG. 24 , alarm history management will be described. Indoor monitor  15   a  is connected to an apparatus such as a fire alarm or an emergency button apparatus, for example. It is now assumed that indoor monitor  15   a  has received a signal indicating that a fire has occurred, from a fire alarm, for example. Alternatively, it is assumed that indoor monitor  15   a  has received a signal indicating that a button has been pressed, for example, from the emergency button apparatus. 
     Indoor monitor  15   a  notifies server  11  that a signal has been received from an apparatus such as a fire alarm or an emergency button apparatus (step S 131 ). Indoor monitor  15   a  may transmit the signal type information (for example, information indicating whether the signal is from a fire alarm or a signal from the emergency button apparatus) to server  11 . 
     In response to the notification of step S 131 , server  11  transmits  200  OK to indoor monitor  15   a  (step S 132 ). 
     In response to the notification of step S 131 , server  11  transmits a push notification to mobile terminal  16   a  (step S 133 ). After receiving the push notification, mobile terminal  16   a  notifies the owner, for example, by icon display on the display or by voice. 
     After reception of the activation operation of the history management application from the owner, mobile terminal  16   a  displays alarm information (step S 134 ). For example, mobile terminal  16   a  displays alarm information such as the alarm information  91   e  illustrated in  FIG. 21 . 
     In a case where mobile terminal  16   a  notifies the owner of the push notification with an image (icon), mobile terminal  16   a  may notify the owner of the alarm type. For example, in a case where mobile terminal  16   a  receives the push notification based on the fire alarm, mobile terminal  16   a  displays an image of the push notification related to the fire alarm. In addition, in a case where mobile terminal  16   a  has received a push notification based on the emergency button apparatus, mobile terminal  16   a  displays an image of the push notification related to the emergency button apparatus. This allows the owner to recognize that a fire has occurred or the emergency button is pressed with an icon indicating a push notification. 
       FIG. 25  is a sequence diagram illustrating an operation example of history management of the intercom system. History management of messages issued from an manager will be described with reference to  FIG. 25 . Server  11  is connected to a terminal apparatus used by a manager of apartment building  1  via a network such as a LAN installed in apartment building  1 . The terminal apparatus may be a personal computer, for example. Using the terminal apparatus, the manager creates a text message addressed to a resident of apartment building  1 , for example. 
     The terminal apparatus converts the text message created by the manager into an image file (step S S 141 ). 
     The terminal apparatus transmits the message converted into the image file in step S 141  to server  11  (step S 142 ). 
     In response to reception of the message transmitted in step S 142 , server  11  transmits  200  OK to the terminal apparatus (step S 143 ). 
     Server  11  stores the message transmitted in step S 142  in the storage section (step S 144 ). 
     In response to reception of  200  OK in step S 143 , the terminal apparatus transmits 
     INVITE to server  11  (step S 145 ). 
     In response to reception of the INVITE transmitted in step S 145 , server  11  sends a push notification to mobile terminal  16   a  (step S 146 ). 
     In response to the reception of the push notification transmitted in step S 146 , mobile terminal  16   a  attempts to obtain the image stored in server  11  (image transmission request) (step S 147 ). Mobile terminal  16   a  stores the image transmitted from server  11  in the storage section. 
     In response to the image transmission request from mobile terminal  16   a  in step S 147 , server  11  transmits  200  OK including the image of the message (step S 148 ). 
     For example, when the history management application is activated, mobile terminal  16   a  displays the message received in step S 148  on the display in chronological order (step S 149 ). 
     As described above, push notification receiver  101   a  of mobile terminal  16   a  receives a push notification from the push server. Information acquirer  101   b  accesses server  11  in response to reception of the push notification by push notification receiver  1016   a,  and obtains event information related to the history of intercom system from server  11 . Display section  101   c  displays event information related to the history of the intercom system on a display. Display section  101   c  displays event information related to the history of the intercom system on the display in scroll-display in chronological order. This enables the resident of room  4  to view event information related to the intercom system by using mobile terminal  16   a.    
     Each of functional blocks used in the description of the above embodiments is typically implemented as an LSI which is an integrated circuit. Each of functions may be individually formed into one chip, or part or the whole of the functions may be incorporated into one chip. Here, the chip is referred to as the LSI, however, it may be called IC, system LSI, super LSI, ultra LSI depending on the degree of integration. 
     In addition, the method of forming an integrated circuit is not limited to LSI, and it may be implemented by a dedicated circuit or a general-purpose processor. It is also allowable to utilize a Field Programmable Gate Array (FPGA) that is programmable after fabrication of the LSI or utilize a reconfigurable processor that is reconfigurable in connections and settings of circuit cells inside the LSI. 
     Furthermore, with the future advent of an integrated circuit technology that would replace the LSI brought by advances in semiconductor technologies or other derivative technologies, it would be of course possible to implement functional block integration using the new technology. Application of biotechnology, etc. may be conceivable. The above embodiments may be combined with each other. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is useful for an intercom system installed in an apartment building. 
     REFERENCE SIGNS LIST 
     
         
           1  Apartment building 
           2  Control room 
           3  Lobby 
           4  Room 
           5  Entrance 
           11  Server 
           12  Telephone 
           13  Lobby intercom 
           14  Camera 
           15   a,    15   b  Indoor monitor 
           16   a,    16   b  Mobile terminal 
           17  Entrance intercom 
           21 ,  31 ,  41 ,  51 ,  61  Controller 
           22 ,  32 ,  42 ,  52 ,  62  Storage section 
           23 ,  33 ,  43 ,  53 ,  63  Communicator 
           34 ,  44 ,  54 ,  64  Voice processor 
           35 ,  45 ,  57 ,  67  Operator 
           46 ,  55 ,  65  Image processor 
           56 ,  66  Display 
           216   a,    71   b  Call controller 
           21   b  Push notifier 
           616   a,    101   a  Push notification receiver 
           61   b  Telephone connector 
           61   c  Camera connector 
           71   a  Extension number receiver 
           816   a,    83   d  Connector 
           81   b  Registration information acquirer 
           81   c  Registration information display section 
           82   a  Registration information transmitter 
           82   b  Push ID receiver 
           82   c  Push notifier 
           82   d  Camera information transmitter 
           83   a  Registration information receiver 
           83   b  Push ID acquirer 
           83   c  Push ID transmitter 
           101   b  Information acquirer 
           101   c  Display section