Communication system having authenticating function

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a communication system in which a communication terminal that communicates with an external communication device is centrally managed by a computer that serves as a central control device, and communication that performs authentication communication between a responder and the communication terminal. Regarding the system.

【0002】

[Conventional technology]

Conventionally, a communication system using an IC card or a magnetic card as a response device has been used for lifting ski resorts, sorting luggage, and managing entry and exit. In such a communication system, the interrogator side that communicates with the responder controls the reader / writer that directly communicates with the responder and the reader / writer, analyzes the signal received from the responder, and analyzes the signal received from the responder. A communication terminal provided with a personal computer (hereinafter referred to as a PC) which is a control device for creating a signal to be transmitted to a response device, and a central control device for central management using the PC of the communication terminal as a slave. It is composed of a PC that becomes.

【0003】

In the conventional communication system as described above, the communication system composed of the communication terminal and the control device on the interrogator side has a system configuration as shown in the block diagram of FIG. That is, a plurality of readers / writers 50 that communicate with the responder.₁~50_nIndividually, PC51₁~51_nIs connected and controlled. In addition, PC51₁~51_nAre slaves, and these PC51s₁~51_nA LAN (Local Area Network) is constructed with PC52, which is the host of.

【0004】

Such a communication system will be briefly described by taking as an example when it is used in an entry / exit system or the like. Reader / Writer 50 is a magnetic card that records personal information such as the time the owner can enter the room and the card ID.₁~50_nAfter inserting it into the room, the owner enters the password to perform the authentication operation and opens and closes the door to enter or leave the room. Now the magnetic card is a reader / writer 50₁It is assumed that it was inserted in. At this time, the password is entered by the owner, and the reader / writer 50₁When the magnetic card is authenticated, communication is performed and the personal information of the magnetic card is read out.

【0005】

This personal information is the reader / writer 50₁PC51 to control₁When it is sent to, it is judged whether the owner can enter or leave the room, and it is judged that it is possible, the reader / writer 50₁Send a command signal to open the door leading to. Then reader / writer 50₁Controls the unlocking of the door and communicates so that the magnetic card records the time when the owner entered and exited the room. In addition, the information on entering and leaving the room of the magnetic card owner is PC51.₁Is sent to the host PC 52, and the location of the owner can be managed by the PC 52. Also, with this PC52, the PC51 that becomes a slave₁~51_nAbnormality can be managed.

【0006】

Further, in such a communication system, in recent years, an IC card is used instead of a magnetic card because of its convenience. At this time, the IC card and the reader / writer are provided with authentication means for generating a rolling code, and the reader / writer and the IC card determine whether or not the other party requesting communication with each other is appropriate. , It enhances its safety.

【0007】

[Problems to be Solved by the Invention]

Thus, multiple reader / writer 50₁~50_nIndividually connected PC51₁~51_nWhile controlling with, these PC51₁~51_nIn a communication system in which a LAN is constructed by a PC 52 and a PC 52, a PC is installed in each communication terminal, which complicates the system. Therefore, the introduction cost and the maintenance cost of the system are high, and the management thereof is complicated.

【0008】

Further, in order to simplify the above system, a hub as a repeater is provided between a plurality of readers / writers and a host PC, and a LAN is directly constructed by the reader / writer and the host PC. It is also possible to do it. However, when such a communication system is used, security functions such as a rolling code and a personal identification number exchanged between the reader / writer and the responder are provided between the reader / writer and the host PC. Absent. Therefore, when the reader / writer determines that an inappropriate responder is appropriate, spoofing may occur in which communication from the responder to the host PC is performed as it is.

【0009】

In view of these problems, an object of the present invention is to provide a communication system that simplifies the communication system on the interrogator side having a plurality of communication terminals and enhances the security of the communication. To do.

【0010】

[Means for solving problems]

The communication system according to claim 1 is a central communication system that controls a plurality of communication terminals that communicate with other communication devices and the communication terminals, and exchanges information about the communication terminals and the other communication devices. In a communication system having a control device, a switching means for switching a connection line between the central control device and the plurality of communication terminals, and an authentication means for authenticating whether or not the communication terminal is appropriate. It is characterized by having a repeater composed of.

【0011】

The communication system according to claim 2 is the communication system according to claim 1, wherein the switching means selects an input from a plurality of inputs according to the output of the authentication means and multiplexes them into one output path. It is characterized in that it is a multiplexer.

【0012】

The communication system according to claim 3 is a central communication system that controls a plurality of communication terminals that communicate with other communication devices and the communication terminals, and exchanges information about the communication terminals and the other communication devices. In a communication system having a control device, a level shifter for converting a voltage level between a signal transmitted from the central control device and a signal transmitted from the communication terminal and the communication terminal are appropriate. It is characterized by having a repeater including an authentication means for authenticating and a switching means for controlling connection and disconnection of a connection line between the central control device and the communication terminal by the output of the authentication means. To do.

【0013】

The communication system according to claim 4 has means for authenticating whether or not the other communication device is appropriate for the communication terminal in the communication system according to any one of claims 1 to 3. The authentication process performed between the communication terminal and the other communication device and the authentication process performed between the communication terminal and the repeater are performed independently.

【0014】

The communication system according to claim 5 is used in the communication system according to claim 4 for an authentication process added to a signal transmitted from the communication terminal by the authentication means provided in the repeater. The signal is detected to determine whether or not the communication terminal is appropriate, and the communication terminal performs a specific arithmetic process on the authentication signal to obtain a signal for the communication terminal to authenticate the repeater. It is characterized by generating.

【0015】

The communication system according to claim 6 has means for authenticating whether or not the other communication device is appropriate for the communication terminal in the communication system according to any one of claims 1 to 3. When the communication terminal determines that the other communication device is appropriate, a signal indicating that the other communication device is appropriate is transmitted from the other communication device to the repeater, and this signal is transmitted. In the repeater, the authentication means determines whether or not the communication terminal is appropriate based on the above, and when the authentication means determines that the communication terminal is appropriate, the switching means. It is characterized in that the communication terminal and the central control device are connected to each other.

【0016】

The communication system according to claim 7 is the communication system according to claim 6, wherein the authentication means detects a signal indicating that the other communication device is appropriate and the communication terminal is appropriate. It is characterized in that the communication terminal generates a signal for authenticating the repeater by performing a specific arithmetic process on the detected signal as well as determining whether or not the signal has been detected.

【0017】

BEST MODE FOR CARRYING OUT THE INVENTION

The first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a communication system according to the present embodiment. FIG. 2 is a block diagram showing an internal structure of the multiplexer used in the present embodiment. FIG. 3 is a block diagram showing the internal structure of the IC card and the reader / writer used in the present embodiment. 4 and 5 are time charts showing the operation of the communication system shown in FIG. Hereinafter, NG means that the person to be authenticated is inappropriate when authentication is performed, and OK means that the person to be authenticated is appropriate when authentication is performed.

【0018】

The communication system shown in FIG. 1 is a reader / writer 2 which is a communication terminal that performs non-contact communication with the IC card 1.₁~2_nAnd the reader / writer 2₁~2_nThe repeater 3 connected to the repeater 3 and the reader / writer 2 connected to the repeater 3₁~2_nIt is composed of PC4 which is a central control device that centrally manages.

【0019】

In such a communication system, the repeater 3 is a reader / writer 2 as shown in FIG.₁~2_nMultiplexer 5 that switches the connection line between and PC4, and reader / writer 2₁~2_nDetects the authentication signal (rolling code) transmitted from the reader / writer 2 by this authentication signal.₁~2_nAuthentication circuit 6 and reader / writer 2₁~2_nIt has an arithmetic circuit 7 for generating an authentication signal obtained by applying a predetermined arithmetic processing f1 () to the authentication signal transmitted from.

【0020】

Also, the reader / writer 2 in FIG.₁~2_nFigure 3 shows an example of the internal configuration of. That is, the reader / writer 2 in FIG.₁~2_nAs shown in the reader / writer 2 of FIG. 3, the tuning circuit 21 that transmits / receives a signal to / from the IC card 1 and the response signal received by the tuning circuit 21 are demoted and the command signal transmitted from the control circuit 23 is modulated. The modulation / demodulation circuit 22 to be used, the control circuit 23 to control the entire device and generate an instruction signal, and the authentication circuit to transmit an authentication signal from the control circuit 23 and to authenticate the IC card 1 or the repeater 3 by the authentication signal. It is composed of 24 and an arithmetic circuit 25 that sends an authentication signal from the control circuit 23 and performs a predetermined arithmetic processing f2 () on the authentication signal.

【0021】

Reader / writer 2 with such a configuration₁~2_nAnd when the power is turned on to the repeater 3, the reader / writer 2₁~2_nAnd the repeater 3 starts the authentication operation. Now, assuming that this authentication operation is performed by the reader / writer 2 and the repeater 3, the operation will be described with reference to FIG. First, in the repeater 3, an arbitrary signal is generated by the arithmetic circuit 7 as an authentication signal Rc1 for the reader / writer 2 to perform an authentication operation (STEP1), and this authentication signal Rc1 is transmitted to the reader / writer 2 (STEP1). STEP2). The authentication signal Rc1 is an arbitrary signal and is not a signal to which the calculation f1 () is performed by the calculation circuit 7.

【0022】

When the reader / writer 2 receives this authentication signal Rc1, the control circuit 23 determines from the control circuit 23 whether or not the authentication signal Rc1 is a signal subjected to the calculation f1 () in the repeater 3. The authentication signal Rc1 is sent to. Now, since this authentication signal Rc1 is not a signal to which the operation f1 () is applied, the authentication result is NG, and the reader / writer 2 does not authenticate the repeater 3 as improper (STEP 3).

【0023】

At the same time, the authentication signal Rc1 is sent from the control circuit 23 to the arithmetic circuit 25 to perform arithmetic f2 () (STEP 4). In this way, the signal f2 (Rc1) subjected to the calculation f2 () in the calculation circuit 25 is sent to the control circuit 23 as the authentication signal Rc2, and is transmitted from the control circuit 23 to the repeater 3 (STEP 5).

【0024】

When the repeater 3 receives the authentication signal Rc2, the authentication circuit 6 determines whether or not the authentication signal Rc2 is a signal for which the calculation f2 () is performed in the reader / writer 2. Now, since this authentication signal Rc2 = f2 (Rc1) is a signal to which the operation f2 () is applied, the authentication result is OK, and the repeater 3 authenticates the reader / writer 2 as appropriate (STEP 6). At the same time, the authentication signal Rc2 is subjected to the calculation f1 () by the calculation circuit 7 (STEP 7). In this way, the signal f1 (Rc2) subjected to the calculation f1 () in the calculation circuit 7 is transmitted to the reader / writer 2 as the authentication signal Rc3 (STEP 8).

【0025】

When the reader / writer 2 receives the authentication signal Rc3, the authentication signal Rc3 is sent from the control circuit 23 to the authentication circuit 24. Now, since this authentication signal Rc3 = f1 (Rc2) is a signal to which the operation f1 () is applied, the authentication result is OK, and the reader / writer 2 authenticates the repeater 3 as appropriate (STEP 9). At this time, similarly to STEP4 and STEP5, the authentication signal Rc3 is sent from the control circuit 23 to the arithmetic circuit 25 to perform arithmetic f2 () (STEP10). In this way, the signal f2 (Rc3) subjected to the calculation f2 () in the calculation circuit 25 is sent to the control circuit 23 as the authentication signal Rc4, and is transmitted from the control circuit 23 to the repeater 3 (STEP 11).

【0026】

When the repeater 3 receives the authentication signal Rc4, the authentication circuit 6 determines whether or not the authentication signal Rc4 is a signal subjected to the calculation f2 () in the reader / writer 2 as in STEP6. Now, since this authentication signal Rc4 = f2 (Rc3) is a signal to which the operation f2 () is applied, the authentication result is OK, and the repeater 3 authenticates the reader / writer 2 as appropriate (STEP 12). In this way, in STEP1 to STEP12, if the repeater 3 authenticates the reader / writer 2 twice while the reader / writer 2 and the repeater 3 communicate with each other, the reader / writer 2 and the repeater 3 are authenticated. It is confirmed that mutual authentication has been performed with 3.

【0027】

Communication such as STEP1 to STEP12 is the reader / writer 2₁~2_nAnd repeater 3 in turn, reader / writer 2₁~2_nMutual authentication is performed between and the repeater 3. In STEP6, when the authentication result is NG in the authentication circuit 6 of the repeater 3, the processing operation after STEP1 is performed again. Further, in STEP 9, when the authentication result is NG in the authentication circuit 24 of the reader / writer 2, a signal that has not been arithmetically processed by the arithmetic circuit 25 is transmitted to the repeater 3. At this time, since the repeater 3 does not authenticate the reader / writer 2, the operation from STEP 1 is performed again. When either the reader / writer 2 or the repeater 3 does not authenticate as a result of performing such an operation a plurality of times, the authentication result is regarded as NG and the authentication process is terminated.

【0028】

As mentioned above, reader / writer 2₁~2_nAuthentication processing such as STEP1 to STEP12 is performed between the repeater 3 and the repeater 3, and the repeater 3 is the reader / writer 2.₁~2_nAt the same time as storing the authentication result of the above in the authentication circuit 6, the authentication result is transmitted from the authentication circuit 6 to the PC4. After that, the reader / writer 2 from the repeater 3₁~2_nTo, reader / writer 2₁~2_nSends an authentication signal at regular intervals to detect whether or not the IC card is recognized, and at the same time, reader / writer 2₁~2_nHowever, in order to recognize the IC card 1, each emits a weak radio wave. At this time, if the authentication results of both the reader / writer 2 and the repeater 3 are not OK, the authentication signal is not transmitted from the repeater 3 to the reader / writer 2. That is, the reader / writer 2 is no longer used for communication.

【0029】

The authentication process performed between the IC card 1, the reader / writer 2, and the repeater 3 after both the reader / writer 2 and the repeater 3 have authenticated will be described below with reference to FIG. Now, when the IC card 1 is tuned to the weak radio wave transmitted from the reader / writer 2 by a tuning circuit (not shown) as in STEP50, power is generated by the rectifier circuit (not shown) in the IC card 1. , It is supplied to each circuit in the IC card 1, and the IC card 1 turns ON. When the IC card 1 is turned on, the IC card 1 transmits a response signal R1 from the tuning circuit to recognize that it is close to the reader / writer 2 (STEP 51). When the reader / writer 2 receives this response signal R1 by the tuning circuit 21, the control circuit 23 recognizes the existence of the IC card 1 (STEP 52).

【0030】

Now, as shown in FIG. 5, it is assumed that the operations of STEP50 to STEP52 are performed between the IC card 1 and the reader / writer 2, and the reader / writer 2 recognizes the IC card 1. At this time, after mutual authentication between the reader / writer 2 and the repeater 3, the operation of STEP1a to STEP9a corresponding to STEP1 to STEP9 in FIG. 4 is again between the reader / writer 2 and the repeater 3. It is done in. The authentication signals Rc1a to Rc3a correspond to the authentication signals Rc1 to Rc3 in FIG.

【0031】

When such an operation is performed, the reader / writer 2 generates an authentication signal Rc4a in which the operation circuit 25 performs the operation f2 () on the authentication signal Rc3a and sends it to the control circuit 23 (STEP 20). The control circuit 23 generates an instruction signal C1 to which the authentication signal Rc4a is added (STEP 21). This instruction signal C1 is modulated by the modulation / demodulation circuit 22 and then transmitted from the tuning circuit 21 (STEP 22).

【0032】

When the IC card 1 receives this instruction signal C1 by the tuning circuit, it is determined whether or not the authentication signal Rc4a added to this instruction signal C1 has been subjected to the operation f2 () (STEP 23). Now, since this authentication signal Rc4a = f2 (Rc3a) is a signal to which the operation f2 () is applied, the authentication result is OK, and the IC card 1 authenticates the reader / writer 2 as appropriate. At the same time, the authentication signal Rc4a is subjected to the predetermined operation f3 () to generate the authentication signal Rc5a (STEP 24). The response signal R2 to which this authentication signal Rc5a is added is transmitted from the tuning circuit (STEP 25). When the IC card 1 authenticates the reader / writer 2, data for recognizing that communication is possible is added to the data in the response signal R2. Further, the authentication signal Rc5a is added to the response signal R2 regardless of the authentication result.

【0033】

In this way, while the processing operations of STEP20 to STEP25 are being performed between the IC card 1 and the reader / writer 2, the reader / writer 2 and the repeater 3 are like STEP1b to STEP12b. The authentication operation is performed. That is, after the repeater 3 transmits the authentication signal Rc3a in STEP8a, when there is no response from the reader / writer 2 for a certain period of time, the authentication signal Rc1b corresponding to the authentication signal Rc1 is transmitted as in STEP1b corresponding to STEP1 in FIG. Generate. After that, the operations as shown in STEP2b to STEP12b corresponding to STEP2 to STEP12 in FIG. 4 are performed. The authentication signals Rc1b to Rc4b in STEP1b to STEP12b correspond to the authentication signals Rc1 to Rc4 in FIG.

【0034】

While mutual authentication processing such as STEP1b to STEP12b is being performed between the reader / writer 2 and the repeater 3, the reader / writer 2 tunes the response signal R2 transmitted from the IC card 1 in STEP25. Receive at 21. When the reader / writer 2 receives the response signal R2, it demodulates with the modulation / demodulation circuit 22 and then detects the authentication signal Rc5a with the control circuit 23 (STEP 26). Further, the control circuit 23 recognizes whether or not the IC card 1 is in a communicable state from the response signal R2.

【0035】

This authentication signal Rc5a is sent to the authentication circuit 24, and it is determined whether or not the signal has been subjected to the calculation f3 () by the authentication circuit 24 (STEP 27). Now, since this authentication signal Rc5a = f3 (Rc4a) is a signal to which the calculation f3 () is applied, the authentication result is OK, and the reader / writer 2 authenticates the IC card 1 as appropriate. At the same time, the authentication signal Rc5a is subjected to the operation f2 () to generate the authentication signal Rc6a (STEP 28). When the authentication result of either the IC card 1 or the reader / writer 2 is NG, the arithmetic circuit 25 transmits the authentication signal Rc5a without the arithmetic f2 () to the repeater 3.

【0036】

By the way, since the authentication result of the reader / writer 2 is OK with the IC card 1, it can be recognized in STEP26 that communication is possible from the response signal R2. At this time, the authentication signal Rc6a is transmitted to the repeater 3 (STEP 29). It is determined whether or not the authentication signal Rc6a is subjected to the calculation f2 () in the authentication circuit 6 (STEP 30). Now, since this authentication signal Rc6a = f2 (Rc5a) is a signal to which the operation f2 () is applied, the authentication result is OK, and the repeater 3 authenticates the reader / writer 2 as appropriate.

【0037】

In this way, if the repeater 3 is authenticated as appropriate, it means that the reader / writer 2 and the repeater 3 and the IC card 1 and the reader / writer 2 are mutually authenticated. Therefore, the connection line between the reader / writer 2 and the PC 4 is connected by the multiplexer 5 of the repeater 3. By connecting the reader / writer 2 and the PC 4 in this way, the IC card 1 communicates with the PC 4 via the reader / writer 2 and the repeater 3.

【0038】

Further, when the authentication result of the IC card 1 or the reader / writer 2 is NG, the authentication signal subjected to the calculation f2 () is not detected in STEP30, and the authentication result of the authentication circuit 6 becomes NG. At this time, the operation from STEP1a is performed again. Further, after such an authentication process is performed a plurality of times, when all the authentication results are NG, a signal indicating the authentication result is transmitted from the authentication circuit 6 of the repeater 3 to the PC4, and the PC4 is the IC card 1 and the reader. -Recognize that mutual authentication has not been performed between the writer 2. When the PC4 recognizes it in this way, it notifies the user of the IC card 1 that an error has occurred by displaying an error message by a display means provided in the reader / writer 2.

【0039】

A second embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing a communication system according to the present embodiment. FIG. 7 is a block diagram showing an internal structure of the repeater used in the present embodiment. The communication system shown in FIG. 6 includes a reader / writer 2 having an internal structure as shown in FIG. 3, which is a communication terminal that performs non-contact communication with the IC card 1, and a repeater 3'connected to the reader / writer 2. , PC4 which is a control device of a reader / writer 2 connected to the repeater 3'.

【0040】

Further, as shown in FIG. 7, the repeater 3'has a level shifter 8 that converts the voltage level of the signal transmitted / received when communicating with the reader / writer 2 and the voltage level of the signal transmitted / received when communicating with the PC 4. , Switch 9 that connects and disconnects the communication path between the reader / writer 2 and the level shifter 8, and the authentication circuit 10 that detects the authentication signal transmitted from the reader / writer 2 and authenticates the reader / writer 2 by this authentication signal. And an arithmetic circuit 11 that applies a predetermined arithmetic processing f1 () to the authentication signal transmitted from the reader / writer 2.

【0041】

The operation of the communication system using the repeater 3'with such a structure is the same as the operation in the time charts of FIGS. 4 and 5 described in the first embodiment. That is, the reader / writer 2 and the repeater 3'are determined in the authentication circuits 24 and 10 whether the authentication signal is a signal subjected to the calculation of f1 () and f2 (), respectively, so that the repeater 3' , The reader / writer 2 is authenticated, and the received authentication signals are subjected to the operations f2 () and f1 () in the arithmetic circuits 25 and 11, respectively, and the authentication signals are transmitted.

【0042】

Then, after such a mutual authentication operation is performed between the reader / writer 2 and the repeater 3'and it is authenticated that they are appropriate for each other, the reader / writer 2 transmits a weak radio wave from the tuning circuit 21. Then, it recognizes whether or not the IC card 1 is close to each other. Further, the repeater 3'transmits an authentication signal to the reader / writer 2 at regular intervals in order to detect that the reader / writer 2 has recognized the IC card 1. At this time, when the reader / writer 2 recognizes that the IC card 1 is close to the IC card 1, the reader / writer 2 uses the authentication signal transmitted after the repeater 3'authenticates that the reader / writer 2 is appropriate. Authenticate 3'. Then, the control circuit 23 generates an instruction signal to which the authentication signal obtained by performing the calculation f2 () is added to the authentication signal, modulates it with the modulation / demodulation circuit 22, and then transmits it from the tuning circuit 21.

【0043】

When the IC card 1 receives the command signal from the reader / writer 2, it determines whether or not the authentication signal detected from this command signal is a signal to which the calculation f2 () is applied, and calculates the authentication signal. A response signal with an authentication signal subjected to f3 () is transmitted. Further, data indicating whether or not the IC card 1 is in a communicable state is added to this response signal according to the authentication result.

【0044】

When the reader / writer 2 receives this response signal in the tuning circuit 21, the reader / writer 2 demodulates the response signal in the modulation / demodulation circuit 22, and then detects the authentication signal in the control circuit 23. At this time, the control circuit 23 recognizes whether or not the IC card 1 is in a communicable state from this response signal. Then, the authentication circuit 24 determines whether or not the authentication signal detected by the control circuit 23 is a signal to which the calculation f3 () has been performed. At this time, if the IC card 1 is authenticated by this authentication signal, the calculation circuit 25 performs the calculation f2 () on the authentication signal detected by the control circuit 23, and then transmits the authentication signal to the repeater 3'. ..

【0045】

When the repeater 3'receives this authentication signal, the authentication circuit 10 determines whether or not the authentication signal is a signal for which calculation f2 () has been performed. At this time, when the authentication signal is recognized as a signal to which the calculation f2 () is applied and the reader / writer 2 is authenticated, the switch 9 is connected and the connection line between the disconnected reader / writer 2 and the PC 4 is connected. Is connected. In this way, the IC card 1 can communicate with the PC 4 via the reader / writer 2 and the repeater 3'.

【0046】

In a communication system that performs such authentication processing, since the level shifter 9 is provided in the repeater 3', the input / output interface on the PC4 side is set to RS232C standard, and the input / output interface on the reader / writer 2 side is set to RS485 standard. It can be made to correspond. By making the input / output interface on the reader / writer 2 side compatible with the RS485 standard in this way, the distance between the reader / writer 2 and the repeater 3'can be extended up to 100 m.

【0047】

In the communication system of the first embodiment, the level shifter 9 used in the second embodiment is provided between the multiplexer 5 and the PC 4 in the repeater 3, so that the reader / writer 2₁~2_nSince the input / output interface on the side can be made compatible with the RS485 standard, the distance can be extended.

【0048】

Further, although the description has been made using a communication response device that performs non-contact communication such as an IC card, the present invention is not limited to such a response device, and a communication response device that performs contact communication such as a magnetic card may be used. .. When communicating in contact with each other, an input / output interface is provided instead of using a tuning circuit for transmitting and receiving signals from the responder as in the first and second embodiments for the reader / writer. Allows communication between the reader / writer and the responder.

【0049】

[Effect of the invention]

According to the communication system of claim 1 or 2, since the repeater having the authentication means controls the switching of the connection line between the plurality of communication terminals and the central control device, an inappropriate communication terminal is determined. be able to. Further, one central control device can control a plurality of communication terminals.

【0050】

According to the communication system according to claim 3, since the connection and disconnection of the connection line between the communication terminal and the central control device is controlled by the repeater having the authentication means, it is possible to identify an inappropriate communication terminal. it can. Further, since a level shifter is provided in the repeater, the repeater and the communication terminal can be connected by making the interface on the communication terminal side compatible with a stable standard even in long-distance transmission such as RS485. You can extend the distance between them.

【0051】

Since the communication system according to claims 4 to 7 has an authentication means for determining whether or not another communication device is appropriate for the communication terminal, the improper communication device requests communication. At that time, the communication path between the communication terminal and the communication device is cut off, so that a more secure communication system is formed.

[Simple explanation of drawings]

[Figure 1]

The block diagram which shows the structure of the communication system used in 1st Embodiment.

[Figure 2]

The block diagram which shows the internal structure of the repeater used in the communication system of FIG.

[Fig. 3]

The block diagram which shows the internal structure of the reader / writer used in the communication system of this invention.

[Fig. 4]

A time chart showing the operation of the communication system used in the present invention.

[Fig. 5]

A time chart showing the operation of the communication system used in the present invention.

[Fig. 6]

The block diagram which shows the structure of the communication system used in 2nd Embodiment.

[Fig. 7]

The block diagram which shows the internal structure of the repeater used in the communication system of FIG.

[Fig. 8]

The block diagram which shows the structure of the conventional communication system.

[Explanation of symbols]

1 IC card 2 Reader / writer (communication terminal) 3,3'repeater 4 PC (central controller) 5 Multiplexer 6 Authentication circuit 7 Arithmetic circuit 8 level shifter 9 switch 10 Authentication circuit 11 Arithmetic circuit 21 Tuning circuit 22 Modulation / demodulation circuit 23 Control circuit 24 Authentication circuit 25 Arithmetic circuit