JP2000332913A - Method for controlling incoming call of data terminal device and data terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To download data necessary to a data terminal device by allowing a transmission source to make a call out to the data terminal device. SOLUTION: The incoming call control part 106 of a data terminal device 101 analyzes the telephone number of a caller received through a line exchange network, a communication line 108, a changeover switch 103 and a modem 104, holds the terminals b-c of the switch 103 in the closed state and receives data following the telephone number of the caller in the case the telephone number of the caller coincides with a telephone number registered previously with a storage device 107. When the telephone number of the caller is not registered, the terminals a-b of the switch 103 are closed, and a telephone set 102 is connected to the line exchange network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incoming call control method for a data terminal device for transmitting and receiving data via a circuit switching network, and a data terminal device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a data terminal device has been used as a device for transmitting and receiving various data such as update data and update software via a circuit switching network such as a public telephone network. (See, for example,
No. 7860, JP-A-2-13058, JP-A-10-322466, JP-A-10-56520, and JP-B-7-75379.

That is, in FIG. 6, a host computer or server 601 and a data terminal device 603 are connected via a circuit switching network 602. When transmitting various data from the host computer or the server 601 to the data terminal device 603, the data terminal device 603 generally receives a call from the host computer or the server 601 because a call is also used in the same circuit-switched network. It could not be determined if it was a data communication or a call, unless it received a call (off-hook) and received data. Therefore, when an incoming call is received, if it is a data communication, it may be received as it is, but if it is a telephone call, the data terminal device 603 makes no sense if it receives it.

[0004] Therefore, the data terminal device 603 is generally configured so as to originate a call only (dial from the data terminal device 603) and not permit an incoming call. Therefore,
Even when the host computer 601 wants to actively transmit various data such as business data and business applications of the data terminal device 603 to the data terminal device 603, or to transmit update data thereof, the data terminal device 603 is also required. , The required data can be downloaded only when the host computer or the server 601 receives the transmission from the data terminal device 603.

[0005]

As described above, since the data terminal device 603 is dedicated to outgoing calls and does not permit incoming calls, the host computer or server 601 actively sends various data to the data terminal device 603. If you want to download at any time,
There is a problem that data communication cannot be performed by making a telephone call to the data terminal device 603. It is an object of the present invention to enable a data transmission source to make a call to a data terminal device and perform necessary data communication. Another object of the present invention is to make it possible to receive a call to a specific data transmission source and perform necessary data communication. Another object of the present invention is to make it possible to perform necessary data communication from a data source at any time with a simple configuration by using a number display service.

[0006]

According to the present invention, there is provided an incoming call control method for a data terminal device for transmitting and receiving data via a circuit switching network, wherein a signal received by the data terminal device via the circuit switching network is provided. Identifies a call and data, and in the case of data, the data is received by the data terminal device. A signal received by the data terminal device via a circuit switching network such as a public telephone network identifies either a call or data. If the signal is data, the signal arrives at the data terminal device.

According to the present invention, in a method for controlling the termination of a data terminal device for transmitting and receiving data via a circuit switching network, a signal received by the data terminal device via the circuit switching network is transmitted from a source. A signal to which identification information for identification is added, and the data terminal device determines the identification information so that the signal is received by the data terminal device when the identification information is a source registered in advance. An incoming call control method for a data terminal, comprising: The signal received by the data terminal device via the circuit switching network is a signal to which identification information for identifying the source is added. The identification information is discriminated by the data terminal device and the identification information is registered in advance. If it is the source of the call, the data is received at the data terminal device. Here, the data terminal device receives the identification information by a first modem, determines the source, and if the identification information is that of a previously registered source, the data terminal device follows the identification information. The data may be received by a second modem. Further, a caller telephone number used in a number display service may be used as the identification information.

According to the present invention, in a data terminal device for transmitting and receiving data via a circuit switching network, the identification information of the transmission source received via the circuit switching network is determined, and the transmission source which has been previously permitted to receive a call is determined. In the case of the identification information indicating the following, the data following the identification information is received. The data terminal device determines the identification information of the transmission source received via a circuit switching network such as a public telephone network, and, in the case of the identification information indicating the transmission source permitted to receive the call in advance, the data following the identification information To receive.

Further, according to the present invention, in a data terminal device for transmitting and receiving data via a circuit switching network, a receiving means for receiving a signal via the circuit switching network, and a transmission source permitted to receive a call are represented. Storage means for pre-registering identification information; and determining whether or not the identification information of the transmission source received by the reception means matches the identification information registered in the storage means. There is provided a data terminal device, comprising: incoming control means for controlling the receiving means so as to receive data subsequent to information. The receiving means receives a signal such as a call or data via a circuit switching network. In the storage means, identification information indicating a source that is permitted to receive a call is registered in advance. The incoming call control means determines whether or not the identification information of the transmission source received by the reception means matches the identification information registered in the storage means. When the identification information matches, the data following the identification information of the transmission source is determined. The receiving means is controlled so as to receive the data. When the incoming call control means determines that the identification information of the transmission source received by the receiving means does not match the identification information registered in the storage means, the incoming call control means connects the circuit switching network to another communication device. Thus, the receiving means may be configured to be controlled.

Further, according to the present invention, in a data terminal apparatus for transmitting and receiving data via a circuit switching network, switching means for receiving a signal via the circuit switching network, and selecting the circuit network by the switching means. A modem and a communication device to be selectively switched and connected, storage means for preliminarily registering identification information indicating a transmission source permitted to receive a call, and identification information of a transmission source received by the switching means being registered in the storage means. Discriminating whether or not the information coincides with the identification information; controlling the switching means so as to receive the data following the identification information of the transmission source via the modem when the information coincides with the identification information; There is provided a data terminal device comprising: incoming control means for controlling the switching means so as to connect a signal from a network to the communication device. The switching means receives a signal via the circuit switching network. Phone or fax
And the like are connected so as to be selectively switched to the line network by the switching means.
In the storage means, identification information indicating a source that is permitted to receive a call is registered in advance. The incoming call control means determines whether or not the identification information of the transmission source received via the switching means matches the identification information registered in the storage means. And controlling the switching means so as to receive the data to be transmitted via the modem, and to connect a signal from the circuit switching network to the communication device when the data does not match.

Further, according to the present invention, in a data terminal apparatus for transmitting and receiving data via a circuit switching network, the circuit switching network includes a communication device, a first modem for receiving a telephone number, and a second modem for receiving data. Switching means for selectively switching connection to the modem, storage means for pre-registering identification information indicating a transmission source permitted to receive a call, and identification of a transmission source received by the first modem via the switching means. Discriminating whether the information matches the identification information registered in the storage means, and when the information matches, the switching means so that the data following the identification information of the transmission source is received by the second modem. A data terminal comprising: switching control means for controlling switching and switching control of the switching means so as to connect a signal from the circuit switching network to the communication equipment when they do not coincide with each other. Location is provided. The switching means selectively connects the circuit switching network to a communication device, a first modem for reading a telephone number, and a second modem for receiving data. In the return means, identification information indicating a source permitted to receive a call is registered in advance. The incoming call control means determines whether or not the source identification information read by the first modem via the switching means matches the identification information registered in the storage means. Switching means for controlling the switching means so that the data following the original identification information is received by the second modem, and the switching means so as to connect a signal from the circuit switching network to the communication equipment when the data does not match. Control. Here, a caller telephone number used in a number display service may be used as the identification information.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an incoming call control method and a data terminal device for a data terminal device according to an embodiment of the present invention will be described. It shall be configured. FIG. 5 shows a signal format used in each of the embodiments.
This is a signal format used when data and voice are transmitted by the data terminal device using the number display service of T). When the number display service is received, first, as shown in FIG. 5, a caller's telephone number 501 unique to the caller is transmitted, and then a ringing tone is generated on the receiving side. The data or voice 502 following the telephone number 501 is configured to be received by the receiving side.

As described above, when a call is made to the data terminal device using the number display service, before receiving the call, the data terminal device determines whether or not the caller has been registered in advance to perform data communication. If the call can be determined, normal incoming calls can be made. As a result of the determination, if the caller (for example, the host computer) is registered in advance so as to perform data communication, the call is received. Can be turned. In each of the embodiments described below, a caller telephone number in the number display service is analyzed by a data terminal device to determine whether or not the caller is a caller registered in advance so as to receive a call. Has been realized.

FIG. 1 is a block diagram of a data terminal device according to the first embodiment of the present invention. In FIG. 1, a data terminal device 101 includes a changeover switch 103 as a changeover means or a reception means, a modem 104, a central processing unit (CPU) 105, and a storage device 107 as a storage means.
It has. The common terminal b of the changeover switch 103 is connected to a line switching network such as a public telephone network via a communication line (telephone line) 108, and the terminal a is connected to the telephone 1 as a communication device.
02 and terminal c is connected to the modem 104. Note that the telephone 102 may be another communication device such as a facsimile.

The modem 104 has an incoming call control unit 106 as an incoming call control unit realized as one function of the CPU 105.
It is connected to the. The storage device 107 including a hard disk or a non-volatile memory or the like is preliminarily registered with a list of telephone numbers of transmission sources that allow incoming calls. It should be noted that since the data terminal device 101 does not make sense to receive a call, a communication device capable of transmitting data, such as a host computer, is selected as a source that accepts an incoming call.
The incoming call control unit 106 controls switching of the changeover switch 103 according to whether or not the caller telephone number of the caller input via the modem 104 is a telephone number stored in the storage device 107, as described later. Do. FIG.
3 is a flowchart for explaining the processing of FIG.

Hereinafter, the first embodiment will be described with reference to FIGS. 1 and 2. First, as an initial state, the changeover switch 103 has terminals bc closed while the power of the data terminal apparatus 101 is on, and a signal received from the circuit switching network via the communication line 108 is input to the modem 104. State. In the data terminal device 101 configured as described above, when a call is received from a host computer or a server (not shown) as a transmission source using the number display service, the modem 104 receives an incoming call. Read the first caller telephone number (501 in FIG. 5) of the received signal,
Next, the read caller telephone number is output to the incoming call control unit 106. Here, the caller telephone number is unique identification information indicating a caller.

Next, incoming call control section 106 determines whether or not the caller telephone number has been received (step S20 in FIG. 2).
1). In this case, since the caller's telephone number has been received, the incoming call control unit 106 reads out a list of telephone numbers permitted to receive calls registered in the storage device 107 in advance (see step S202 in FIG. 2), and It is determined whether or not the same telephone number as the number is registered (see step S203 in FIG. 2). As a result of the determination, if there is a corresponding telephone number, the data terminal device 101 itself receives an incoming call while keeping the terminals bc of the changeover switch 103 closed (see step S204 in FIG. 2).

On the other hand, if the telephone number is not registered in the list, it is determined that the telephone number is not the communication partner of the data terminal apparatus 101, and the changeover switch 103 is controlled to close the terminals ab (FIG. 2). In step S205), the telephone 102 or another communication device (not shown), such as a facsimile, connected to the outside is switched to the circuit switching network.

When the power of the data terminal apparatus 101 is off, the incoming call control section 106 cannot operate. Therefore, in this case, all incoming calls need to be connected to the external telephone 102 or the like. Therefore, as a default state when the power of the data terminal apparatus 101 is turned off, the changeover switch 103 is set in a state where the terminals ab are closed. On the other hand, when the data terminal device 101 is powered on, as described above, the changeover switch 103 is connected to the terminal b.
-C is controlled by the incoming call control unit 106 to close.

As described above, by registering in advance the telephone number of the host computer or the server, etc., on which the incoming call is permitted on the data terminal device 101 side in the storage device 107, the data transmission from the registered host computer, the server, etc. From a device having a function to a data terminal device 10
If it is desired to actively download various data such as update data and application files at an arbitrary time with respect to the data terminal device 1 from the host computer or the like,
01, and necessary data can be transmitted.

Therefore, various data such as a program file can be sent to the data terminal device 101 via the circuit switching network at an arbitrary time according to the will of the administrator of the host computer or the like. Also, when downloading various data from a device having a data transmission function, such as a host computer, to the data terminal device, or in a system in which a large number of data terminal devices are connected to a host computer or a server via a circuit switching network, the host computer is used. Alternatively, when it is desired to download data terminals sequentially from the server while avoiding concentration of downloads from the server to each data terminal device, it is not possible to wait for a call from the data terminal device when it occurs. There is an effect that data transmission to the data terminal device can be controlled for convenience.

Further, by registering the telephone numbers of all the devices capable of transmitting data connected to the system in the storage device 107, it is possible to analyze only the caller telephone number and determine whether the received signal is a call. It can be determined whether the data is data. Furthermore, when the signal received by the data terminal device 101 is a telephone call, it is possible to receive a call at the telephone 102. Further, by using the caller telephone number of the number display service as the identification information indicating the caller, it is not necessary to use special identification information, and the configuration can be simplified.

FIG. 3 is a block diagram of a data terminal device according to a second embodiment of the present invention, which is an example extended to a general data terminal device. The second embodiment differs from the first embodiment mainly in that a changeover switch 304, a data communication modem 306 for data communication, and a data communication control unit 309 are added. In general, since the calling party telephone number 501 and the subsequent data or voice 502 shown in FIG. 5 use different modulation schemes, different modems are required. Therefore, in the second embodiment, the caller telephone number received by the incoming call control unit 308 via the modem 305 for reading the caller telephone number is determined, and after the call is received, the data communication modem 306 is switched by the changeover switch 304. , The data is received.

That is, the data terminal device 301 is provided with the changeover switch 30 as the first changeover means constituting the changeover means.
3. a changeover switch 304 as a second changeover means constituting a changeover means, a modem 305 for reading a caller telephone number as a first modem, a data communication modem 306 for data communication as a second modem, Processing unit (CPU)
307 and a storage device 310 as storage means. Note that the changeover switch 303 and the changeover switch 304 also constitute receiving means. A common terminal e of the changeover switch 303 is connected to a circuit switching network via a communication line (telephone line) 311, a terminal d is connected to an external telephone 302 as a communication device, and a terminal f is a common terminal of the changeover switch 304. h. Note that the telephone 302
Another communication device such as a facsimile may be used.

The terminal g of the changeover switch 304 is connected to the modem 30
5 is connected to an incoming call control unit 308 as an incoming call control unit realized as one function of the CPU 307, and a terminal i is connected to the CPU 207 via the data communication modem 306.
Is connected to a data communication control unit 309 as data communication control means realized as one of the functions. In the storage device 310 constituted by a hard disk, a non-volatile memory, or the like, a list of the telephone numbers of the caller who is permitted to receive a call is registered in advance. The incoming call control unit 308 controls switching of the changeover switches 303 and 304 according to whether or not the caller's telephone number input via the modem 305 is a telephone number registered in the storage device 310. FIG.
9 is a flowchart for explaining processing of the incoming call control unit 308.

The second embodiment will be described below with reference to FIGS. 3 and 4. First, as an initial state, while the power of the data terminal apparatus 301 is on, the terminals ef of the changeover switch 303 are turned on. Are closed, and a state is received in which a signal received via the circuit switching network is input to the switch 304. The changeover switch 304 is kept in a state where the terminals hg are closed. In the data terminal device 301 configured as described above, when a call is received from a host computer or a server (not shown) serving as a transmission source using the number display service, the modem 305 receives an incoming call. The caller telephone number (501 in FIG. 5) at the head of the received signal is read, and the read caller telephone number is output to the incoming call control unit 308. Here, the caller telephone number is unique identification information indicating a caller.

The incoming call control unit 308 determines whether or not the caller telephone number has been received (see step S401 in FIG. 4). At this time, since the incoming call control unit 308 has received the caller's telephone number, it reads out a list of telephone numbers for which incoming calls are registered in the storage device 310 in advance (see step S402 in FIG. 4). It is determined whether the same telephone number as the telephone number is registered (see step S403 in FIG. 4). If it is determined that the telephone number is registered in the list, the terminal ef of the switch 303 is kept closed and the terminal hi of the switch 304 is switched to switch the modem. Control is performed so as to close (see step S404 in FIG. 4). As a result, the data subsequent to the caller telephone number is transmitted to the data communication modem 30 through the changeover switches 303 and 304.
6 and is demodulated here and the data communication control unit 30
9, the data communication control unit 309 performs various data processing.

On the other hand, if it is determined that the telephone number does not exist in the list, it is determined that the telephone number is not its own communication partner, and the terminals de of the changeover switch 303 are closed (see step S405 in FIG. 4). ), Another communication device (not shown) such as a telephone 302 or a facsimile which is branch-connected to the outside is switched to a circuit switching network and connected. Note that, similarly to the first embodiment, when the power of the data terminal device 301 is off, the incoming call control unit 308 cannot operate, so that all incoming calls need to be transferred to the external telephone 302 or the like. is there. Therefore, the changeover switch 303 is set as a default state when the power of the data terminal device 301 is turned off.
The terminals de are kept closed.

On the other hand, when the power is turned on to the data terminal device 301, the changeover switch 303 is connected to the terminals ef.
Is controlled by the incoming call control unit 308 to close.
Similarly, the changeover switch 304 is maintained in a state where the terminals gh are connected. In the second embodiment,
In addition to the effect similar to that of the first embodiment, the use of both the telephone number reading modem 305 and the data communication modem 306 has the effect of having versatility.

As described above, the incoming call control method for a data terminal according to each of the above embodiments is the incoming call control method for a data terminal device that transmits and receives data via a telephone line and a circuit switching network. Data terminal device 1 via
01, 301 identifies the call or data, and if the signal is data, the data terminal 10
1, 301.

In the method for controlling the termination of a data terminal device for transmitting and receiving data via a circuit network, signals received by the data terminal devices 101 and 301 via the circuit switching network can transmit data from a host computer or the like. Is a signal to which identification information for identifying a unique transmission source is added. When the identification information is determined by the data terminal devices 101 and 301 and the identification information is that of a pre-registered transmission source, the data The terminal is set to receive a call. Here, the data terminal device receives the identification information by the first modem (modem 305), determines the transmission source, and if the identification information is of a pre-registered transmission source, the data terminal device performs the identification. The data following the information is
Received by a modem (data communication modem). Further, as an example of the identification information, a caller telephone number is used, but other identification information may be used.

The data terminal device 101 or 301 according to each of the above embodiments is a data terminal device that transmits and receives data via a circuit switching network, and transmits the identification information of the transmission source received via the circuit switching network. It is characterized in that, in the case of identification information indicating a source that has been permitted to receive a call in advance, data subsequent to the identification information is received.

In a data terminal apparatus for transmitting and receiving data via a circuit switching network, receiving means (switches 103 and 30) for receiving a signal via the circuit switching network.
3, 304) and storage means (storage devices 107, 310) for registering in advance identification information indicating a source permitted to receive a call.
And determining whether or not the identification information of the transmission source received by the reception unit matches the identification information registered in the storage unit, and when the identification information matches, receives data subsequent to the identification information of the transmission source. And the incoming call control means (incoming call control units 106 and 308) for controlling the receiving means. When the incoming call control means determines that the identification information of the transmission source received by the receiving means does not match the identification information registered in the storage means, the incoming call control means connects the circuit switching network to another communication device. The receiving means is controlled as described above.

In a data terminal apparatus for transmitting and receiving data via a circuit switching network, switching means (switches 103 and 30) for receiving a signal via the circuit switching network.
3) and the modems 104 and 305 and the communication device 10 selectively switched and connected to the line network by the switching means.
Storage means (storage devices 107, 310) for registering in advance 2, 302 and identification information indicating a source that is permitted to receive a call
And determining whether or not the identification information of the transmission source received through the switching unit matches the identification information registered in the storage unit. When the identification information matches, the data following the identification information of the transmission source is determined. Incoming control means for controlling the switching means so as to receive the signal via the modem, and controlling the switching means so as to connect a signal from the circuit switching network to the communication equipment when the signals do not match. It is characterized by:

Further, in a data terminal device for transmitting and receiving data via a circuit switching network, a communication device 302 and a first modem (modem 30) for reading a telephone number are connected to the circuit switching network.
5) and switching means (selection switches 303 and 304) for selectively switching and connecting to a second modem for receiving data (modem 306 for data communication), and identification information indicating a transmission source permitted to receive a call are registered in advance. Storage means (storage device 31)
0) and whether or not the identification information of the transmission source received by the first modem via the switching means matches the identification information registered in the storage means. And controlling the switching means so that the data following the identification information is received by the second modem, and the switching means is connected to connect the signal from the circuit switching network to the communication equipment when the data does not match. And an incoming call control unit (incoming control unit 308) for controlling. Here, the caller's telephone number is used as an example of the identification information, but other identification information may be used.

Therefore, conventionally, when a data transmission source such as a host computer wants to actively download data or application files at an arbitrary time, it has not been possible to make a telephone call to the data terminal device for communication. If the telephone number of a device having a data transmission function such as a host computer is registered in advance in the incoming call permitted telephone number list, the data terminal device can be transmitted to the data terminal device at an arbitrary time according to the intention of the data transmission side administrator of the host computer or the like. Various data can be sent. This makes it difficult to know when the data terminal device will be downloaded in a hurry to download various types of data such as update data and update programs, or to connect to the data terminal device one after another because many data terminal devices are connected. There is an effect that the data terminal device can be controlled at the convenience of the host computer management department without waiting for a call from the terminal.

[0037]

According to the present invention, it is possible to make a call from a data transmission source to a data terminal device and download necessary data such as update data and an update program to the data terminal device. In addition, by using the caller telephone number of the number display service, it is not necessary to add special identification information, so that it is possible to realize a simple configuration at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of a data terminal device according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining processing of the data terminal device according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a data terminal device according to a second embodiment of the present invention.

FIG. 4 is a flowchart for explaining processing of a data terminal device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a signal format used in the embodiment of the present invention.

FIG. 6 is a configuration diagram of a general data communication system.

[Explanation of symbols]

101, 301, 603 Data terminal device 102, 302 Telephone as communication device 601 Host computer 602 Circuit switching network 103, 303, 304 Switching switch 104 as switching means , 305... Modems 105, 307... CPUs 106, 308... Incoming call control sections 107, 310... Storage devices 306, data communication modems 309. Data communication control unit as data communication control means

Claims (9)

[Claims] 1. An incoming call control method for a data terminal device for transmitting and receiving data via a circuit switching network, wherein a signal received by the data terminal device via the circuit switching network is identification information for identifying a transmission source. Is added, and when the identification information is determined by the data terminal device and the identification information is from a source registered in advance, the signal is received by the data terminal device. An incoming call control method for a data terminal. 2. The data terminal device receives the identification information by a first modem, determines a transmission source, and, if the identification information is of a transmission source registered in advance, adds the identification information to the identification information. 2. The method according to claim 1, wherein the subsequent data is received by a second modem. 3. The method according to claim 1, wherein the identification information is a caller telephone number. 4. A data terminal device for transmitting and receiving data via a circuit switching network, comprising: determining identification information of a transmission source received via the circuit switching network; Wherein the data terminal device receives data following the identification information. 5. A data terminal device for transmitting and receiving data via a circuit switching network, wherein a receiving means for receiving a signal via said circuit switching network and identification information indicating a source of which the incoming call is permitted is registered in advance. Storage means for determining whether or not the identification information of the transmission source received by the reception means matches the identification information registered in the storage means, and when the identification information matches, the data following the identification information of the transmission source is determined. A data terminal device, comprising: incoming control means for controlling the receiving means so as to receive the data. 6. The incoming call control means, when judging that the identification information of the transmission source received by the receiving means does not match the identification information registered in the storage means, switches the circuit switching network to another communication device. 6. The data terminal device according to claim 5, wherein said receiving means is controlled so as to be connected. 7. A data terminal device for transmitting and receiving data via a circuit switching network, comprising: switching means for receiving a signal via said circuit switching network; and selectively switching connection to said circuit network by said switching means. A modem and a communication device, storage means for pre-registering identification information indicating a transmission source permitted to receive a call, and identification information of the transmission source received via the switching means coincides with the identification information registered in the storage means. The switching means is controlled to receive, via the modem, data subsequent to the identification information of the transmission source when they match, and a signal from the circuit switching network when the data does not match. A data terminal device comprising: incoming call control means for controlling the switching means so as to connect to the communication device. 8. A data terminal device for transmitting and receiving data via a circuit switching network, wherein the circuit switching network is selectively used as a communication device, a first modem for reading a telephone number and a second modem for receiving data. Switching means for switching connection, storage means for pre-registering identification information indicating a source permitted to receive a call, and identification information of a source received by the first modem via the switching means in the storage means It is determined whether or not the identification information matches the registered identification information. When the identification information matches, the switching control is performed on the switching means so that the data following the identification information of the transmission source is received by the second modem. A data terminal device, comprising: an incoming call control unit that controls the switching unit so that a signal from the circuit switching network is connected to the communication device when not in use. 9. The data terminal device according to claim 4, wherein the identification information is a caller telephone number.