JP3716712B2 - Voice communication method, voice communication system, and communication unit apparatus thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, for example, conceals call contents between fixed telephone stations connected to each other via a public telephone network and calls contents between a fixed telephone station and a mobile radio station connected to a mobile communication network. The present invention also relates to a voice communication method, a voice communication system, and a communication unit device thereof.
[0002]
[Prior art]
In general, voice communication between a fixed telephone station installed in a home and another fixed telephone station is a public telephone line network (hereinafter referred to as a network of transmission lines) that is composed of a large number of exchanges and a network between them. The public telephone network). This public telephone network is a so-called analog telephone network that transmits a voice signal transmitted from a fixed telephone station to a call partner via an analog switch. When voice communication is performed using such an analog telephone network, A third party can eavesdrop on the content of the call in a relatively easy manner.
[0003]
On the other hand, in a mobile communication system such as a digital cellular phone system that performs voice communication wirelessly, encryption technology is used in a so-called wireless section between a mobile radio station and a base station to prevent eavesdropping on the contents of a call from others. The idea to do is made. For example, Japanese Patent Application Laid-Open No. 5-219049 relates to a wireless communication device used in an automobile telephone system, a mobile phone system, etc., and scrambles an audio signal transmitted via a wireless line to prevent wiretapping from others. In addition, Japanese Patent Laid-Open No. 8-293915 discloses a digital communication system for transmitting an audio signal as a digital signal. In the digital communication system, only a specific bit of the digital audio signal is subject to encryption. Is described with respect to a telephone with an encryption function.
[0004]
However, in the mobile communication system as described above, when the voice signal transmitted from the mobile radio station is transmitted to the other party via the public telephone network, that is, voice communication is performed between the fixed telephone station and the mobile radio station. Is performed, the voice signal transmitted from the mobile radio station is converted into the original analog voice signal and transmitted through the public telephone network. However, in the wired section including the public telephone network, there is a sufficient possibility that the wiretapping is illegally conducted by another person in the same manner as the voice communication between the fixed telephone stations.
[0005]
For example, FIG. 8 is a communication state explanatory diagram schematically showing voice communication between a mobile radio station connected to a digital mobile communication network and a fixed telephone station in a general home connected to a public telephone network. In FIG. 8, 47 is a mobile radio station, 48 is a base station connected to the mobile communication switch 49, and 50 is an interchange apparatus for identifying whether a digital radio modulation signal transmitted from the mobile radio station 47 is a voice signal or a data signal. , 51 is a gateway exchange for connecting the mobile communication network to the public telephone network 52, and 53 is connected to the public telephone network 52, for example, connected to each fixed telephone station 54 provided in each home. A subscriber line switch 55 for exchange connection with a plurality of fixed telephone stations, a modem 55 for converting an analog modem signal analog-modulated by the mobile communication switch 49 into an original data signal and outputting it to an information terminal device such as a personal computer If the digital radio modulation signal transmitted from the mobile radio station 47 is an audio signal based on the identification of the mutual switching device 50, the mobile communication switch 49 receives the signal from the base station. When the transmitted digital audio signal is an original analog audio signal and the digital radio modulation signal transmitted from the mobile radio station 46 is a data signal from a personal computer or the like, the data signal transmitted from the base station is an analog signal. Convert to analog modem signal.
[0006]
As shown in FIG. 8, the digital voice signal transmitted from the mobile radio station 47 is transmitted in the state of an encrypted digital voice signal to the mobile communication switch 49 installed in the mobile communication network. From the mobile communication switch 49 to the fixed telephone station 54 connected to the subscriber line switch 53, it is transmitted to the other party in the state of being restored to the original analog voice signal, and illegally eavesdropping from others in such a so-called analog communication section. There was a risk of being done.
[0007]
In voice communication between fixed telephone stations, a method in which an analog voice signal transmitted from each fixed station is once converted into a digital voice signal and the digital voice signal is output to a public telephone network via a modem. By adopting, it is possible to conceal the contents of the call in all communication sections between fixed telephone stations, but between fixed telephone stations adopting such a system and mobile radio stations as described above The voice encoding method and the voice encryption method adopted are different, and voice communication can be performed only between fixed telephone stations.
[0008]
[Problems to be solved by the invention]
As described above, in the voice communication between the fixed telephone stations mutually connected to the conventional public telephone network, the voice signal transmitted from the fixed telephone station is transmitted in the public telephone network or the like in the state of an analog voice signal. Therefore, in a so-called analog communication section including this public telephone network, a third party can eavesdrop on the contents of the call using a relatively easy means, and can make a call on information that is difficult to be known to others. There was a problem that such important information could not be leaked to others. In addition, even if a method of digitizing mutual audio signals between fixed telephone stations and transmitting them to the communication partner is adopted between such fixed telephone stations and mobile radio stations connected to the mobile communication network. The problem is that voice communication can only be performed between fixed telephone stations and voice communication cannot be performed between a fixed telephone station and a mobile radio station because the voice encoding method used is different. There was a point.
[0009]
As a means for concealing the contents of a call in all communication sections including the so-called analog communication section as described above, for example, it is conceivable to provide an analog concealment device between subscriber line switches connected to a public telephone network. However, it is a heavy burden on the system provider to newly add such a secret device to the system for a secret call between specific users.
[0010]
In addition, as a method of transmitting an audio signal without going through the public telephone network 51, for example, there is a method using a dedicated line. However, it is costly to install a dedicated line with many fixed telephone stations. In addition, there are many problems in laying a dedicated line with a specific fixed telephone station, such as securing a laying space. There is no dedicated line service for voice communication with a specific mobile radio station.
[0011]
The present invention has been made in order to solve the above-described problems, and between a fixed telephone station connected to a public telephone network and a mobile radio station connected to a mobile communication network such as a digital portable electric network. In voice communication in Japan, the content of the call can be concealed in all communication sections with the communication partner, and the same method can be used without any other measures between fixed telephone stations mutually connected to the public telephone network A novel voice communication system, voice communication method, and communication unit apparatus thereof that can conceal the contents of a call and can easily realize secret communication with a communication partner without distinguishing between a fixed telephone station or a mobile radio station. The purpose is to provide.
[0012]
[Means for Solving the Problems]
  A voice communication method according to the invention of claim 1 is a voice communication method between terminal stations connected to each other via a public telephone network.Terminal stationIs,Voice input meansInInput audio signalBy A / D converterDigitalLe strangeThe digital audio signalEncrypted and temporarily stored in the data buffer unit, and the synchronized voice encrypted data stored in the data buffer unit is converted by the format conversion unit.Asynchronous formFor audio data signalsConvert and receiveTerminal stationToPreviousReceptionTerminal stationIs,PreviousSendTerminal stationSent fromNonSynchronized audio data signalSynchronized audio encrypted data by the format converterConverted toTemporarily storing the encrypted audio data in the synchronous format after being temporarily stored in the data buffer unit;thisDecryptedDigital audio signalBy D / A converteranalogConvertTo the audio output means,PreviousThe contents of calls between the terminal stations are made confidential.
[0013]
  The voice communication system according to the invention of claim 2A public telephone network; a fixed telephone station connected to the public telephone network; a digital mobile communication network connected to the public telephone network; and the fixed telephone connected to any one of the base stations of the digital mobile communication network A digital mobile radio station that performs voice communication with a station, and a voice encryption unit that is connected to each of the digital mobile radio station and the fixed telephone station and encrypts a digital voice signal that has been digitally converted. Voice decoding means corresponding to the means, a data buffer unit for temporarily storing the encrypted audio data of the synchronization format output from the audio encryption unit, and the synchronous audio encryption stored in the data buffer unit The data is converted into an asynchronous audio data signal and output, while the asynchronous audio data signal sent from the partner station is converted into synchronous audio data A communication unit device having a format conversion unit for converting and outputting to the audio decoding means via the data buffer unit, and the communication unit device connected to the fixed telephone station converts the communication unit device by the format conversion unit. The asynchronous audio data signal is analog-modulated and then output to the public telephone network, and the communication unit connected to the digital mobile radio station is converted to the asynchronous format converted by the format converter. The voice data signal is output to the base station via the data communication data interface provided in the digital mobile radio station.Is.
[0014]
  The voice communication system according to the invention of claim 3The digital mobile radio station switches the communication mode from the voice communication mode to the data communication mode, and outputs the asynchronous voice data signal output from the communication unit device to the base station.Is.
[0015]
  A communication unit device according to the invention of claim 4Used by connecting to a data interface for data communication provided in a digital mobile radio station,Audio input / output means for inputting / outputting audio signals, and the audio input / output meansOutput fromIsDigitally convertedDigital audio signalDarkVoice encryptionmeansWhen,The voice decoding means corresponding to the voice encryption means;Voice encryptionmeansEncrypted bySynchronousVoice encrypted dataTemporarilyAccumulationData buffer unit, and the synchronized voice encrypted data stored in the data buffer unit.Asynchronous formFor audio data signalsconversionOutput to the mobile radio station, while converting the asynchronous audio data signal input via the mobile radio station into synchronous audio data, and the audio decoding via the data buffer unit To outputFormat converterAndIt is provided.
[0016]
  A communication unit device according to the invention of claim 5 is:Used between a public telephone network and a fixed telephone station connected to the public telephone network.Fixed telephone interface unit for inputting / outputting analog voice signals to / from a fixed telephone station, and the fixed telephone interface unitThroughEnteredDigitally convertedDigital audio signalDarkVoice encryptionmeansWhen,The voice decoding means corresponding to the voice encryption means;Voice encryptionmeansEncrypted bySynchronousVoice encrypted dataTemporarilyAccumulationData buffer unit, and the synchronized voice encrypted data stored in the data buffer unit.Asynchronous formFor audio data signalsconversionOn the other hand, the asynchronous voice data signal input via the public telephone network is converted into synchronous voice encrypted data and output to the voice decoding means via the data buffer unit.Format converter to output and output from this format converterPreviousAsynchronous audio data signals are modulated by analogSaidPublic telephoneOn the netoutputThe analog modulation signal input via the public telephone network is returned to the original asynchronous audio data signal and output to the format conversion unit.With an asynchronous modem.
[0017]
  The communication unit device according to the invention of claim 6 is terminated in a public telephone network.MultipleWith subscriber linesConnected to theseBetween private branch exchangesAnd a given subscriber lineProvided inUsed,Before being connected to the private branch exchangeA private branch exchange interface unit for inputting / outputting analog voice signals to / from an extension telephone station that has selected a predetermined subscriber line, and this private branch exchange interface unitThroughEnteredDigitally convertedDigital audio signalDarkVoice encryptionmeansWhen,The voice decoding means corresponding to the voice encryption means;Voice encryptionmeansEncrypted bySynchronousVoice encrypted dataTemporarilyAccumulationData buffer unit, and the synchronized voice encrypted data stored in the data buffer unit.Asynchronous formFor audio data signalsconversionOn the other hand, the asynchronous voice data signal input via the public telephone network is converted into synchronous voice encrypted data and output to the voice decoding means via the data buffer unit.Format converter to output and output from this format converterPreviousAsynchronous audio data signals are modulated by analogSaidPublic telephoneOn the netoutputThe analog modulation signal input via the public telephone network is returned to the original asynchronous audio data signal and output to the format conversion unit.With an asynchronous modem.
[0018]
  A communication unit device according to the invention of claim 7SaidSuitable for line quality of public telephone networkencryptionThe method is adopted.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a system schematic diagram showing a voice communication system according to an embodiment of the present invention, which is connected between fixed telephone stations mutually connected to a public telephone network and connected to such a fixed telephone station and a mobile communication network. The mobile radio stations are configured to perform voice communication with each other. The voice communication method according to the present invention is applied to a voice communication system in which voice signals are transmitted to each other via a so-called analog communication section including a public telephone network. For example, the voice communication method is connected to a digital telephone network. The same applies to voice communication between a fixed telephone station and a fixed telephone station connected to a public telephone network, and voice communication between a fixed telephone station connected to a digital telephone network and a mobile radio station connected to a mobile communication network. It is possible to apply.
[0020]
In FIG. 1, 1 is a mobile communication network adopting a digital system (for example, a digital mobile phone network, a car telephone network, etc.), 2 is a mobile communication switch for mobile communication provided in the mobile communication network 1, and 3 is mobile A base station 4 connected to the communication exchange 2 via a fixed transmission path 4 moves within a communication area constituted by the base station 3 and can be wirelessly communicated with the plurality of base stations 3. Is a communication unit device for a mobile radio station to which the mobile radio station 4 is connected to carry out the voice communication method according to the present invention. The connection cable 7 for transmitting the digital audio signal is a voice input / output means such as a receiver connected to the communication unit device 5. The digital mobile radio station 4 is provided with a data interface unit for wirelessly transmitting a data signal from a personal computer or the like. A connection cable 6 connected to the communication unit device 5 is a data interface unit of the mobile radio station 4. It is connected to the.
[0021]
Reference numeral 8 denotes a public telephone network constituted by a large number of exchanges and an analog transmission line extending between them as a network, and 9a and 9b are connected to the terminal portion of the public telephone network 8, respectively. Subscriber line switches 10a and 10b that are connected to a plurality of fixed telephone stations installed in the home and perform exchange connection with the plurality of fixed telephone stations are respectively connected to the subscriber lines from the subscriber line switch. The telephone stations 11a and 11b are respectively arranged between the subscriber line switch 9a or 9b and the fixed telephone station 10a or 10b, and are used by connecting the fixed telephone stations 10a or 10b. Device. The fixed telephone station 10a or 10b is connected to the communication unit apparatus 11a or 11b by a modular jack or the like, for example, and the communication unit apparatus 11a or 11b is a wall in a general home so that the modular jack of the conventional fixed telephone station 10a or 10b can be inserted. A modular jack or the like is inserted into a socket (subscriber line terminal) attached to the subscriber line switch 9a or 9b.
[0022]
The mobile communication network 1 and the public telephone network 8 are connected to a common line signal network (not shown) configured to transfer various control signals such as dial numbers by connecting the processors of each exchange with a high-speed transmission line. The communication lines set between the fixed telephone stations or between the mobile radio station 4 and the fixed telephone station 10a are controlled by the processor of each exchange connected to the common line signal network. Based on this, the optimum route is always set.
[0023]
Next, a specific configuration of each communication unit device shown in FIG. 1 will be described. FIG. 2 is a block diagram showing a communication unit device for a fixed telephone station according to the present invention, and FIG. 3 is a block diagram showing a communication unit device for a mobile radio station according to the present invention. First, a communication unit device for a fixed telephone station will be described. Note that the fixed telephone station communication unit apparatus 11a or 11b and the fixed telephone station 10a or 10b shown in FIG. 1 are configured in the same manner, and when there is no need to distinguish between them, the fixed telephone station communication unit. The apparatus 11 and the fixed telephone station 10 will be described.
[0024]
In FIG. 2, reference numeral 12 denotes an analog voice signal input / output to / from the fixed telephone station 10, and a normal call mode (hereinafter referred to as a normal mode) or a secret call mode according to a change signal from the changeover switch 13, for example. A telephone interface unit 14 for switching to either one (hereinafter referred to as a confidential mode), and 14 converts a transmission voice (analog voice signal) from the fixed telephone station 10 output from the telephone interface unit 12 into a digital voice signal. An A / D conversion unit 15 is a speech encoding processing unit that performs encoding processing on the digital speech signal output from the A / D conversion unit 14 by a predetermined encoding method, and 16 is output from the speech encoding processing unit 15. For example, a voice encryption unit that performs encryption processing using, for example, a secret key method on the voice encoded data.
[0025]
Reference numeral 17 denotes a data buffer unit for temporarily storing the encrypted audio data output from the audio encryption unit 16 and the encrypted audio data from the communication partner output from the format conversion unit described later. Reference numeral 18 denotes a data buffer unit. 17 converts the data format of the encrypted audio data stored in the data format 17 into an asynchronous data format, and converts the asynchronous audio data signal received from the asynchronous modem from the communication partner into the original data format and converts it into a data buffer unit. 17 is a format conversion unit for outputting to 17, and 19 is a signal for transmitting an asynchronous audio data signal output from the format conversion unit 18 to a communication partner via the public telephone network 8 which is an analog network, that is, analog modulation. From a communication partner that has been subjected to asynchronous analog modulation Performs analog demodulation asynchronous format of the audio data signal is an asynchronous modem outputs a data signal of the original asynchronous format is demodulated to the format conversion unit 18.
[0026]
Reference numeral 20 denotes an encryption / decryption unit that performs encryption / decryption processing on the encrypted audio data from the communication partner stored in the data buffer unit 17 and extracts the original encoded audio data. Reference numeral 21 denotes an output from the encryption / decryption unit 20. A speech decoding processing unit that performs decoding processing on speech encoded data from a communication partner and extracts a digital speech signal, and 22 is a digital speech signal output from the speech decoding processing unit 21 that is converted from the original analog speech signal. A D / A conversion unit for converting the signal into an analog audio signal output from the D / A conversion unit 22 is output to the fixed telephone station 10 via the telephone interface unit 12, and the voice output unit ( (Not shown) is output as a received voice. Reference numeral 23 denotes an analog transmission line that is selected when responding to a call request to the communication partner or an incoming call from the communication partner and when performing voice communication in the normal mode.
[0027]
As shown in FIG. 2, the communication unit device for a fixed telephone station is provided with, for example, an analog transmission path 23 for making a call request to a communication partner and realizing voice communication in the normal mode and voice communication in the secret mode. The user on the fixed telephone station 10 side can select any desired mode and perform voice communication with the communication partner by operating the changeover switch 13, for example. The fixed telephone station communication unit device 11 is not provided with voice input / output means such as a microphone and a speaker, and the fixed telephone station user is provided in the fixed telephone station 10 regardless of the normal mode or the secret mode. Voice communication with a communication partner is performed using voice input / output means such as a microphone and a speaker.
[0028]
Next, a specific configuration of the communication unit device for mobile radio stations will be described. This mobile radio station communication unit device 5 corresponds to the fixed telephone station communication unit device 11 shown in FIG. 2, and the user on the fixed telephone station 10 side uses the fixed telephone station communication unit device 11. As a result, it is possible to perform secret communication not only between fixed telephone stations but also with mobile radio stations without taking any other means. In FIG. 3, 24 is a voice input unit such as a microphone, 25 is an A / D conversion unit that converts an analog transmission voice input to the voice input unit 24 into a digital voice signal, and 26 is from the A / D conversion unit 25. A speech encoding processing unit 27 that encodes the output digital speech signal by a predetermined encoding method, and 27 performs, for example, encryption processing of a secret key method on the speech encoded data output from the speech encoding processing unit 26 It is a voice encryption unit.
[0029]
In addition, 28 is a data buffer unit for temporarily storing voice encrypted data output from the voice encryption unit 27 and voice encrypted data from a communication partner output from a format conversion unit described later, and 29 is a data buffer unit. The data format of the voice encrypted data stored in 28 is converted into an asynchronous data format and output to the data interface unit 30 of the mobile radio station 4 via the connection cable 6, and the communication received by the mobile radio station 4 A format conversion unit 31 converts the asynchronous audio data signal from the other party into the original data format and outputs it to the data buffer unit 28, and encrypts and decrypts the voice encrypted data from the communication partner stored in the data buffer unit 28. The encryption / decryption unit that performs processing and extracts the original speech encoded data, 32 is the encryption / decryption unit 31 A speech decoding processing unit 33 that performs decoding processing on the speech encoded data from the output communication partner and extracts the original digital speech signal, 33 is a digital speech signal from the communication partner output from the speech decoding processing unit 32. A D / A converter 34 for converting the original analog audio signal, and 34 an audio output unit such as a speaker for outputting the analog audio signal output from the D / A converter 33 to the outside as a received voice.
[0030]
4 is a block diagram showing a specific configuration of the mobile radio station 4 to which the mobile radio station communication unit device 5 shown in FIG. 3 is connected. As shown in FIGS. 3 and 4, the mobile radio station communication unit device 5 is provided with a voice input / output means different from the mobile radio station 4. The user on the mobile radio station 4 side uses the voice input / output means provided in the mobile radio station 4 to perform a voice communication in the normal mode. When the communication is performed, the voice input / output means 24 and 34 provided in the communication unit device 5 are used to make a call with the communication partner. In addition, since a voice encoding processing unit, a voice decoding processing unit, and the like different from the mobile radio station 4 can be provided, at least a lower bit rate (for example, 2 kbps to a voice encoding method provided in the mobile radio station 4). 4 kbps, etc.) can be provided. For example, even when applied to a voice communication system having a public telephone network with poor line quality, call quality can be provided. It is also possible to perform good secret communication.
[0031]
Next, the communication operation of the voice communication system according to the present embodiment will be described focusing on the operations of the communication unit devices 5 and 11. As described above, in the voice communication system according to the present invention, a desired voice encoding method and encryption method can be appropriately selected according to the line quality of the public telephone network to be applied. In order to realize the voice communication method, it is necessary to use the same voice encoding method and encryption method between terminal stations that perform voice communication, and this is applied to each communication unit device 5 and 11. It is assumed that the same voice encoding method and encryption method suitable for a voice communication system are used.
[0032]
First, a case where a call is made between the fixed telephone station 10a and the fixed telephone station 10b will be described. For example, in FIG. 1, when a call request is made from the fixed telephone station 10a to the fixed telephone station 10b, the user on the fixed telephone station 10a side operates the dial key of the fixed telephone station 10a to be the fixed telephone station that is the other party of the call. Enter the 10b phone number. At this time, the normal mode is selected by the changeover switch 13 in the communication unit device 11a, and a call request from the fixed telephone station 10a is output to the subscriber line switch 9a through the analog transmission line 23. The subscriber line switch 9a selects the subscriber line switch 9b connected to the fixed telephone station 10b from the telephone number of the fixed telephone station 10b that is the communication partner, and the subscriber line switch 9b receives a response from the fixed telephone station 10b. It is confirmed. At this time, the normal mode is also selected by the changeover switch 13 in the communication unit device 11b, and the incoming call signal is output from the fixed telephone station 10b to the subscriber line switch 9b through the analog transmission line 23. Then, a communication line of a predetermined route is set between each of the subscriber line exchanges 9a and 9b, and voice communication in the normal mode is started between the fixed telephone station 10a and the fixed telephone station 10b.
[0033]
Next, a case where a call is performed in the secret mode will be described. When each user switches from the normal mode to the call in the secret mode, each user operates the changeover switch 13 provided in the communication unit device 11. When the change-over switch 13 is operated, a change-over signal is input to the telephone interface unit 12, and thereafter, the connection state with the analog transmission line 23 is cut off and a call in the secret mode is performed. When the communication unit device 11 on one fixed telephone station side is switched to the secret mode, a modem signal is output to the other fixed telephone station side. The switch of the secret mode by the modem signal can be confirmed, and the call mode on the local station side can be switched to the secret mode after confirming the switch to the secret mode of the other party. Thus, only one of the other parties does not switch to the secret mode and cannot make a call, and the secret call in the secret mode can be performed between the fixed telephone station 10a and the fixed telephone station 10b.
[0034]
It should be noted that a detecting means for detecting a modem signal is provided so that when one terminal station switches the call mode, the other station detects this and automatically switches between the normal mode and the secret mode. You may comprise.
[0035]
Hereinafter, the operation in the secret mode will be described. When a call is made in the secret mode, the transmitted voice input to the voice input unit of the fixed telephone station on the transmission side (hereinafter referred to as the transmission station side) is input to the A / D conversion unit 14 via the telephone interface unit 12. Is done. The analog audio signal input to the A / D conversion unit 14 is converted into a digital audio signal, and is encoded into audio encoded data by the audio encoding processing unit 15. The voice encoding processing unit 15 selects and uses an encoding method suitable for data transmission in the public telephone network 8, such as the PSI-CELP method, as described above, and performs voice communication via the public telephone network 8. Even so, it is possible to perform high-quality voice communication.
[0036]
The audio encoded data encoded by the audio encoding processor 15 is then subjected to a predetermined encryption process by the audio encryption unit 16 and stored in the data buffer unit 17. The voice encrypted data output from the voice encryption unit 16 is a continuous data signal encoded based on a so-called synchronization signal, and is temporarily stored in the data buffer unit 17 for data format conversion by the format conversion unit 17. Is done. FIG. 5 is a format explanatory diagram for explaining the data format conversion of the audio signal in the present invention. FIG. 5A is a format explanatory diagram showing the data format of the audio encrypted data output from the audio encryption unit 16. FIG. 5B is a format explanatory diagram showing the data format of the encrypted audio data after the format conversion by the format conversion unit 18.
[0037]
The format conversion unit 18 reads out so-called synchronous audio encrypted data stored in the data buffer unit 17 every 8 bits, for example, and sets the data format so that it can be handled in asynchronous data communication before and after each read data. A start bit and a stop bit are added respectively. As a result, the output of the voice encryption unit 16, which is a continuous data signal as shown in FIG. 5A, is converted into an asynchronous voice data signal as shown in FIG. 5B. Since the asynchronous voice data signal output from the format conversion unit 18 cannot be transmitted as it is through the public telephone network 8 or the like, it is analog-modulated by the asynchronous modem 19 and output to the subscriber line switch 9 side. The The data format shown in FIG. 5B is the same data format as the data signal output from a personal computer or the like. In the voice communication method according to the present invention, the voice signal from the transmitting station side is converted into the data signal from the personal computer or the like. It is imitated and output to the subscriber exchange 9.
[0038]
Next, the operation of the fixed telephone station on the receiving side (hereinafter referred to as the receiving station side) will be described. The analog modulated signal transmitted to the receiving station side is first input to the asynchronous modem 19 where it is demodulated into the original asynchronous audio data signal. The asynchronous audio data signal output from the asynchronous modem 19 is output to the format converter 18 where it is converted into audio encrypted data of the original data format. Here, FIG. 5 (c) is a format explanatory diagram showing the data format of the asynchronous audio data signal analog demodulated by the asynchronous modem 19, and FIG. 5 (d) is the original audio cipher converted by the format converter 18. It is a format explanatory drawing which shows the data format of digitized data. The asynchronous audio data signal transmitted through the public telephone network 8 or the like is returned to the original data format as shown in FIG. 5 (d) by the format converter 18 of the communication unit device 10 on the receiving station side. Voice decoding processing or the like can be performed.
[0039]
When an asynchronous audio data signal is input, the format converter 18 first detects a start bit and a stop bit, and extracts audio encrypted data, for example, every 8 bits from the asynchronous audio data signal. The extracted 8-bit audio encryption data is temporarily stored in the data buffer unit 17 and then output to the encryption / decryption unit 20 as synchronous audio encryption data, and transmitted by the encryption / decryption unit 20. Decryption processing is performed according to the encryption method on the station side. For example, when the secret key type encryption method is used in the communication unit device 11 on the transmitting station side, the secret key type encryption method is also used in the communication unit device 11 on the receiving station side, Decryption processing is performed using a decryption key common to the encryption key on the transmitting station side. The original speech encoded data decrypted by the encryption / decryption unit 20 is output to the speech decryption processing unit 21 and subjected to speech decryption processing according to the encryption method on the transmitting station side based on the reproduced synchronization signal. The The original digital audio signal reproduced by the audio decoding processing unit 21 is output to the D / A conversion unit 22, converted to the original analog audio signal, and then output to the fixed telephone station 9 via the telephone interface unit 12. Is done. The audio signal output from the communication unit device 11 is returned to an analog audio signal, and the received voice can be obtained by the audio output unit provided in the fixed telephone station 10 on the receiving station side.
[0040]
In this way, by providing the communication unit device 11 on each of the transmitting station side and the receiving station side, the local station side can perform the voice encoding process and the encryption process on the digital voice signal even in the so-called analog communication section. Can be transmitted to the communication partner, and even if an illegal wiretapping act from a third party is performed, the contents of the call can be concealed.
[0041]
Next, a case where a call is made between the mobile radio station 4 side and, for example, the fixed telephone station 10a will be described. As described above, in the voice communication method according to the present invention, it is possible to realize a secret call with the mobile radio station 4 such as a digital mobile phone by the communication unit device 10 used for the secret call between the fixed telephone stations. In FIG. 1, for example, when voice communication is started between the mobile radio station 4 and the fixed telephone station 10a, the transmitted voice from the mobile radio station 4 side is the base station 3 in the area where the mobile radio station 4 exists → The data is transmitted in the order of the mobile communication exchange 2 → the gateway exchange (not shown) → the public telephone network 8 → the subscriber line exchange 9a and output from the voice output unit of the fixed telephone station 9a. The transmitted voice from the fixed telephone station 10a is transmitted in the reverse direction along the route and output from the voice output unit on the mobile radio station 4 side. On the fixed station 10a side, both voice communication in the normal mode and voice communication in the secret mode are performed using the voice input / output unit of the fixed telephone station 10a. However, the mobile radio station 4 side performs a call in the secret mode. In the case where the communication unit device 5 is disconnected, the voice input / output unit provided in the communication unit device 5 is used to make a call. The operation of the communication unit device 11 on the fixed telephone station 10 side is as described above, and a description thereof will be omitted.
[0042]
The operation on the mobile radio station 4 side will be described. A call request and an incoming call response from the mobile radio station 4 side are performed using the mobile radio station 4 as usual. For example, a predetermined communication line is set between the mobile radio station 4 and the fixed telephone station 10a based on a call request from the mobile radio station 4 side, and the normal mode is set between the mobile radio station 4 and the fixed telephone station 10a. When the voice communication is started, the user on the mobile radio station 4 side makes a call using the mobile radio station 4 as usual. That is, the transmitted voice from the user on the mobile radio station 4 side is switched to voice / data via the voice input unit, A / D conversion unit and voice coding processing unit in the mobile radio station 4 as shown in FIG. The signal is input to the unit 35, is digitally modulated by the digital modulation / demodulation unit 36, and is transmitted from the transmission / reception unit 37 to the base station 3 through the antenna 38. In this case, the communication unit device 5 does not need to be connected to the data interface unit 30 of the mobile radio station 4 and may be connected when performing voice communication in the secret mode.
[0043]
Next, voice communication in the secret mode will be described. When performing voice communication in the secret mode, the user on the mobile radio station 4 side first connects the communication unit device 5 to the data interface unit 30 of the mobile radio station 4, and for example, from the normal mode by a connection request from the communication unit device 5. Switching to the secret mode is performed. The connection request from the communication unit device 5 is made by operating a switch or the like provided in the communication unit device 5 (not shown). When this operation is performed, a connection request signal from the communication unit device 5 is input to the voice / data switching unit 35 in the mobile radio station 4, and the voice / data switching unit 35 switches from the normal mode to the secret mode. Is called. That is, since the voice communication in the secret mode on the mobile radio station 4 side is performed through the data interface unit 30 of the mobile radio station 4, the voice / data in the mobile radio station 4 is used as described above when performing voice communication in the secret mode. A switching signal is input to the switching unit 35 to switch the communication mode of the mobile radio station 4 from the voice communication mode to the data communication mode.
[0044]
When the communication mode of the mobile radio station 4 is switched to the data communication mode, a data signal from a personal computer or the like connected to the data interface unit 30 can be digitally modulated and transmitted to the base station 3. The voice data signal output from the apparatus can be transmitted to the base station 3 in the same manner as a normal data signal. If only the user of the fixed telephone station 10a operates the selector switch 13 to switch the voice communication in the normal mode to the secret mode, the mobile radio station 4 cannot maintain a normal call during that time, and the mobile radio The user on the station 4 side can confirm this state and switch the normal mode on the local station side to the secret mode. The same applies to switching from the secret mode to the normal mode.
[0045]
When a call in the secret mode is started, the voice acquisition means of the mobile radio station 4 can no longer be used. Therefore, the transmitted voice on the mobile radio station 4 side is fixed using the voice acquisition means 24 of the communication unit device 5. It is transmitted to the telephone station 10a. That is, the analog audio signal input to the audio input unit 24 is converted into a digital audio signal by the A / D conversion unit 25, and encoded into audio encoded data by the audio encoding processing unit 26. Similar to the fixed telephone station communication unit device 10a, the voice encoding processing unit 15 selects and uses an encoding method suitable for data transmission in the public telephone network 8, such as the PSI-CELP method. High-quality voice communication can be performed even by voice communication via the telephone network 8.
[0046]
The audio encoded data encoded by the audio encoding processor 26 is then subjected to a predetermined encryption process by the audio encryption unit 27 and stored in the data buffer unit 28. The voice encrypted data output from the voice encryption unit 27 is a continuous data signal encoded based on a so-called synchronization signal, and is temporarily stored in the data buffer unit 28 for data format conversion by the format conversion unit 29. Is done. The format conversion unit 29 reads out so-called synchronous audio encrypted data stored in the data buffer unit 28 every 8 bits, for example, and sets the data format so that it can be handled in asynchronous data communication before and after each read data. A start bit and a stop bit are added respectively.
[0047]
Note that the communication unit device 5 for mobile radio stations also performs data format conversion similar to that of the fixed telephone station 10, and data format conversion as shown in FIGS. 5 (a) and 5 (b) is performed. . As a result, the output of the voice encryption unit 27, which is a continuous data signal as shown in FIG. 5A, is converted into an asynchronous voice data signal as shown in FIG. 5B. The format conversion unit 29 is connected to the data interface unit 30 of the mobile radio station 4 via, for example, the connection cable 6, and the asynchronous audio data signal output from the format conversion unit 29 is connected to the connection cable 6 and the data interface unit 30. Is output to the mobile radio station 4. Asynchronous audio data signals output to the mobile radio station 4 are temporarily stored in the data buffer unit in the mobile radio station 4 and are digitally modulated / demodulated by the digital modulation / demodulation unit 36 in the same manner as data signals from other portable terminal devices such as personal computers After the digital modulation processing is performed, the data is transmitted to the base station 3 in the area where the mobile radio station 4 exists.
[0048]
In the case of normal voice communication, voice encoded data that has been subjected to voice encoding by the mobile radio station 4 is digitally modulated in a data format as shown in FIG. 5A and transmitted to the base station 3. In the case of the voice communication method according to the present invention, the voice encrypted data output from the voice encryption unit 27 is converted into an asynchronous voice data signal as shown in FIG. 3 is transmitted. The digital radio modulated signal from the mobile radio station 4 received by the base station 3 is subjected to digital demodulation processing and output to the mobile communication switch 2.
[0049]
As described above, the mobile communication switch 2 is provided with an interchange function (not shown) for identifying whether the digital radio modulation signal transmitted from the mobile radio station 4 is a voice signal or a data signal. Although processing based on identification is performed, in the case of the voice communication method according to the present invention, the digital radio modulated signal in the secret mode transmitted from the mobile radio station 4 is a voice data signal converted into an asynchronous format, and data Since the data format is similar to the data signal transmitted from a personal computer or the like, the asynchronous audio data signal input to the mobile communication switch 2 is the same as other data signals that are actually audio signals. Analog modulation is performed and output.
[0050]
Usually, since the voice signal transmitted from the mobile radio station 4 is reproduced as the original analog voice by the mobile communication switch 2 and transmitted through the public telephone network 8, for example, the so-called analog communication of the public telephone network 8 or the subscriber line. Although it was possible for a third party to illegally eavesdrop on the content of the call in the section, according to the audio communication method according to the present invention, the audio signal transmitted from the mobile radio station 4 is encoded into a digital signal. Since the public telephone network 8 is transmitted with the processing and further the encryption processing being performed, not only in the wireless section between the mobile wireless station 4 and the base station 3, but also in a communication section called an analog communication section. Eavesdropping from the three parties can be prevented. Since the asynchronous voice data signal subjected to analog modulation cannot be restored to the original voice signal at the fixed telephone station 10a as it is, the fixed telephone station communication unit apparatus 11a as shown in FIG. 1 is provided. The original analog audio signal reproduced by the communication unit device 11a is output to the fixed telephone station 10a.
[0051]
Next, the operation of receiving an audio signal transmitted from the fixed telephone station 10a side to the mobile radio station 4 side will be described. The asynchronous voice data signal subjected to analog modulation in the communication unit device 11a for the fixed telephone station is output to the public telephone network 8 via the subscriber line switch 9a and is sent to the mobile communication switch 2 of the mobile communication network 1. Is transmitted. Then, the mobile communication switching unit 2 returns the voice data signal to the original asynchronous format, which is digitally modulated from the base station 3 and transmitted to the mobile radio station 4.
[0052]
Also, the digital radio modulation signal from the base station received by the mobile radio station 4 is first digitally demodulated by the digital modulation / demodulation unit 36 in the mobile radio station 4, and the voice / data switching means 35, the asynchronous interface unit, the data interface unit. The data is output to the format conversion unit 29 of the communication unit device 5 via 30 or the like. The asynchronous audio data signal input to the format converter 29 is converted into audio encrypted data in the original data format here, and the synchronous audio encrypted data as described above is temporarily stored in the data buffer unit 28. Accumulated. Note that the communication unit device 5 for mobile radio stations also performs data format conversion similar to that of the fixed telephone station 10, and performs data format conversion as shown in FIGS. 5 (c) and 5 (d). . As a result, the audio data signal having the data format as shown in FIG. 5C is converted into the original data format as shown in FIG.
[0053]
The original voice encrypted data temporarily stored in the data buffer unit 28 is output to the encryption / decryption unit 31, and decryption processing is performed by the encryption / decryption unit 31 according to the encryption method on the transmitting station side. . The original speech encoded data decrypted by the encryption / decryption unit 31 is output to the speech decryption processing unit 32 and subjected to speech decryption processing. The audio decoding processing unit 32 also uses an audio decoding method corresponding to the audio encoding method on the transmitting station side, and the original digital audio signal is reproduced based on the reproduced synchronization signal. The digital audio signal reproduced by the audio decoding processing unit 32 is converted to the original analog audio signal by the D / A conversion unit 33 and is output to the outside as the received audio via the audio output unit 34.
[0054]
As described above, in the voice communication system according to the present embodiment, the respective communication unit devices 5 and 11 configured as shown in FIG. 2 or FIG. Alternatively, since voice communication with the communication partner is performed via 11, the user on the fixed telephone station 10 side can make a secret call with the communication partner regardless of the communication partner, and the mobile radio station 4 The user on the side can make a secret call with the fixed telephone station 10 not only in the radio section between the mobile radio station 4 and the base station 3 but also in all communication sections including a so-called analog communication section.
[0055]
In the communication unit device for a mobile radio station as shown in FIG. 3, the communication unit device 5 is simply connected to the data interface unit 30 of the mobile radio station 4 via the connection cable 6 or the like, as shown in FIG. In such a communication unit device for a fixed telephone station, a modular jack or the like of the fixed telephone station 10 is connected to a socket provided in the communication unit device 11, and this communication unit device 10 is laid on a wall in the home by the modular jack or the like. It is only necessary to connect to a socket of a subscriber line, and a secret call with a communication partner can be easily realized without providing an analog concealment device or the like in the subscriber line switch 9 connected to the public telephone network 8. Is possible.
[0056]
Embodiment 2. FIG.
Next, another embodiment of the present invention will be described with reference to FIGS. In the voice communication system according to the above-described embodiment, a fixed telephone station for general home use is shown as a fixed telephone station connected to the public telephone network 8. However, the present invention is a so-called extension telephone connected to a private branch exchange called PBX. The present invention can be applied to a voice communication system in which voice communication is performed by a station. Hereinafter, a voice communication system in which an extension telephone station connected to a private branch exchange is used will be described. FIG. 6 is a system schematic diagram showing a voice communication system according to another embodiment of the present invention, in which the same reference numerals indicate the same or corresponding parts.
[0057]
In FIG. 6, 39 is a private branch exchange which is provided in a government office or a general corporate premises and constitutes a private telephone network, 40 is connected to the private branch exchange, and a fixed type is used for making a telephone call between extension offices connected to the private branch exchange A telephone station (hereinafter referred to as an extension telephone station), 41 is a communication unit device for an extension telephone station that is used by being connected between a private branch exchange 39 and a secret line 42 arbitrarily set as a secret communication line. The extension telephone station communication unit device 41 is not installed between the private branch exchange 39 and each extension telephone station 40 but between the private branch exchange 39 and the public telephone network 8. With this arrangement, all the extension telephone stations 40 connected to the private branch exchange 39 can make a secret call with the communication partner using the extension telephone station communication unit device 41. FIG. It is not necessary to provide the communication unit device 11 as shown in FIG. 2 in each extension telephone station like the fixed telephone stations 10a and 10b shown. Reference numeral 43 denotes a normal communication line for performing normal voice communication and data transmission, and the private branch exchange 39 uses a communication line having an external line number among a plurality of communication lines with the public telephone network 8 as a secret line 42. Set.
[0058]
A specific configuration of the communication unit device 41 shown in FIG. 6 will be described. FIG. 7 is a block diagram showing a communication unit device for an extension telephone station according to the present invention. The basic configuration is the same as that of the communication unit device 11 for a fixed telephone station shown in FIG. In FIG. 7, 45 is a private branch exchange interface unit for inputting / outputting analog voice signals to / from the private branch exchange 39 and switching between the normal mode and the secret mode according to the switching signal from the extension telephone station 40. This is an analog transmission path for responding to a call request to a call partner or an incoming call from a call partner and for voice communication in the normal mode. In the figure, the same reference numerals indicate the same or corresponding parts. Note that the extension telephone station communication unit device 41 is not provided with a selector switch, and the switching between the normal mode and the secret mode in the extension telephone station communication unit device 41 is, for example, a dial signal from the extension telephone station 40. (For example, a combination of a # key and a numeric key).
[0059]
Next, the communication operation of the voice communication system according to the present embodiment will be described focusing on the operation of the communication unit device 41. For example, in FIG. 6, when a normal call request is made from the extension telephone station 40 to the fixed telephone station 10, the user of the extension telephone station 40 has an external line number of the communication line 43 in addition to the telephone number of the fixed telephone station 10, That is, the outside line # 001 or # 002 is selected and transmitted. As a result, a communication line of a predetermined route is set between the private branch exchange 39 and the subscriber line exchange 9 via the communication line 43, and voice communication in the normal mode is performed between the extension telephone station 40 and the fixed telephone station 10. be able to.
[0060]
Next, a case where a call is performed in the secret mode will be described. When each user of the extension telephone station 40 makes a call in the secret mode, each user needs to make a call request via the secret line 42. That is, the user of the extension telephone station 40 selects and transmits the outside line number of the secret line 42, that is, the outside line # 003, in addition to the telephone number of the fixed telephone station 10. At the start of communication, in the communication unit device 41, the private branch exchange interface unit 45 is connected to the subscriber exchange 9 via the analog transmission path 46, whereby the secret line 43 is connected between the private branch exchange 39 and the subscriber line exchange 9. A communication line of a predetermined route via is set. During a call in the normal mode, when the user of the extension telephone station 40 operates a predetermined dial key, this dial signal is detected by the private branch exchange interface unit 45. By detecting this dial signal, voice communication in the normal mode through the analog transmission line 46 is detected. Is switched to voice communication in the secret mode. As described above, dial signals for switching to the secret mode or switching from the secret mode to the normal mode may be set in advance, and the private branch exchange interface unit 45 detects these dial signals. The private branch exchange interface unit 45 is set so as to switch the call mode when it is done.
[0061]
The operation in the secret mode is the same as that of the communication unit device 10 shown in FIG. 2, and a detailed description thereof is omitted. Since the asynchronous voice data signal output from the format converter 18 cannot be transmitted as it is through the public telephone network 8 or the like, analog modulation is performed by the asynchronous modem 19 and the subscriber line is connected via the secret line 42. Output to the exchange 9 side.
[0062]
In addition, the asynchronous voice data signal subjected to analog modulation transmitted from the fixed telephone station 10 side is transmitted through the reverse path and input to the asynchronous modem 19 of the communication unit device 41. The operation on the receiving side is the same as that of the communication unit device 10 shown in FIG. The original analog voice signal output through the format conversion unit 18, the data buffer unit 17, the encryption / decryption unit 20, the speech decryption processing unit 21, the D / A conversion unit 22, and the private branch exchange interface unit 45 passes through the private branch exchange 39. To the extension telephone station 40. The asynchronous voice data signal transmitted from the fixed telephone station 10 side is returned to the original analog voice signal by the communication unit device 41, and the received voice can be obtained by the voice output unit provided in the extension telephone station 40. it can.
[0063]
In this way, by providing the communication unit device 41 for the extension telephone station between the private branch exchange 39 and the public telephone network 8, voice encoding processing and encryption processing are performed on the digital voice signal even in the so-called analog communication section. In this state, the voice signal from the local station side can be transmitted to the communication partner, and the contents of the call can be concealed even if an illegal wiretapping act from a third party is performed. In addition, as shown in FIG. 6, you may comprise so that the communication unit apparatus 11 may be directly connected to the extension telephone station 40. FIG. In this case, a secret call with the communication partner can be realized by the normal communication line 43 without going through the secret line 42.
[0064]
As described above, in the voice communication system according to the present embodiment, the communication unit device 41 configured as shown in FIG. 7 is installed between the private branch exchange 39 and the public telephone network 8, and the communication unit device 41 is installed. Since the voice communication with the communication partner is performed via the mobile phone, the fixed telephone station 10 connected to the public telephone network 8 or the mobile communication at the so-called extension telephone station 40 side user connected to the private branch exchange called PBX, or mobile communication A secret call can be made with a user of a mobile radio station connected to the network 1.
[0065]
【The invention's effect】
  As abovethisAccording to the invention,Has an analog communication sectionThrough the public telephone networkTheVoice communication between terminal stationsTo believeLeaveAThird party in the analog communication sectionbyWiretappingEven if an act is performed, it is difficult to identify whether it is an audio signal, and it is possible to reliably reproduce the content of the call by eavesdroppingCan be prevented.In addition, conversion to an asynchronous audio data signal can be ensured, while an arbitrary audio encoding circuit can be used as appropriate, and concealment of the contents of a call can be realized reliably and easily.
[0066]
  Also,otherAccording to the invention,DigitalWith mobile radio stationsConnected to digital mobile networkBetween base stationsNoIn addition to the line section, it is possible to make the call content confidential in all communication sections,While the voice communication between the digital mobile radio station and the fixed telephone station via the public telephone network having an analog communication section can be concealed,Third party in the analog communication sectionbyWiretappingEven if an act is performed, it is difficult to identify whether it is an audio signal, and it is possible to reliably reproduce the content of the call by eavesdroppingCan be prevented.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing an outline of a voice communication system according to an embodiment of the present invention;
FIG. 2 is a block configuration diagram of a communication unit device for a fixed telephone station used by being applied to the voice communication system shown in FIG. 1;
FIG. 3 is a block configuration diagram of a communication unit device for a mobile radio station used by being applied to the voice communication system shown in FIG. 1;
4 is a block diagram showing a mobile radio station to which the communication unit device shown in FIG. 3 is connected.
FIG. 5 is a format explanatory diagram for explaining format conversion of audio encoded data according to the present invention.
FIG. 6 is a system configuration diagram showing an outline of a voice communication system according to another embodiment of the present invention.
7 is a block configuration diagram of a communication unit device for an extension telephone station used by being applied to the voice communication system shown in FIG. 6;
FIG. 8 is a communication state explanatory diagram schematically showing voice communication by a conventional voice communication system.
[Explanation of symbols]
1 mobile communication network, 2 mobile communication switch, 3 base station, 4 mobile radio station,
5 Communication unit equipment for mobile radio stations, 8 Public telephone network,
9, 9a, 9b Subscriber line switch, 10, 10a, 10b fixed telephone office,
11, 11a, 11b Fixed telephone station communication unit device,
14, 25 A / D conversion unit, 15, 26 speech coding processing unit,
16, 27 Voice encryption unit, 18, 29 Format conversion unit,
19 Asynchronous modem 20, 31 Encryption / decryption unit,
21, 32 voice decoding processing unit, 39 private branch exchange, 40 extension telephone station,
41 Communication unit device for extension telephone office,
45 Private branch exchange interface.

Claims (7)

In the speech communication method between the connected terminal station with each other through a public telephone network, a terminal station on the transmission side, digital converts an audio signal inputted to the audio input means by the A / D conversion unit, the The digital audio signal is encrypted and temporarily stored in the data buffer unit. The synchronous audio encryption data stored in the data buffer unit is converted into an asynchronous audio data signal by the format conversion unit , and then the receiving side. the sending to the terminal station, before Symbol receiving terminal station, converts the pre SL asynchronous format of the audio data signal transmitted from the transmission side terminal station by the format conversion unit in synchronization format of the audio encoded data, decodes the speech encoded data of the synchronous format from temporarily stored in the data buffer unit, the audio the decoded digital audio signal into analog by the D / a converter Outputs to the force means, voice communication method characterized by thereby gave confidentiality the call content between before SL terminal station. A public telephone network; a fixed telephone station connected to the public telephone network; a digital mobile communication network connected to the public telephone network; and the fixed telephone connected to any one of the base stations of the digital mobile communication network A digital mobile radio station that performs voice communication with a station, and a voice encryption unit that is connected to each of the digital mobile radio station and the fixed telephone station and encrypts a digital voice signal that has been digitally converted. Voice decoding means corresponding to the means, a data buffer unit for temporarily storing the encrypted audio data of the synchronization format output from the audio encryption unit, and the synchronous audio encryption stored in the data buffer unit The data is converted into an asynchronous audio data signal and output, while the asynchronous audio data signal sent from the partner station is converted into synchronous audio data A communication unit device having a format conversion unit for converting and outputting to the audio decoding means via the data buffer unit, and the communication unit device connected to the fixed telephone station converts the communication unit device by the format conversion unit. The asynchronous audio data signal is analog-modulated and then output to the public telephone network, and the communication unit device connected to the digital mobile radio station has the asynchronous format converted by the format conversion unit. A voice communication system characterized in that the voice data signal is output to the base station via a data communication data interface provided in the digital mobile radio station . The digital mobile radio station switches the communication mode from the voice communication mode to the data communication mode and outputs the asynchronous voice data signal output from the communication unit device to the base station. The voice communication system according to claim 2 . Audio input / output means used to connect to a data interface for data communication provided in a digital mobile radio station, input / output audio signals, and digital audio converted from the audio input / output means and voice encryption means for encryption of signals, and the audio decoding unit corresponding to the audio encryption means, data for temporarily storing the audio encrypted data encrypted synchronization format by the voice encryption unit A buffer unit, and the synchronous voice encrypted data stored in the data buffer unit is converted into an asynchronous voice data signal and output to the mobile radio station, while being input via the mobile radio station converts the audio data signal in an asynchronous format to synchronous format audio encoded data, and outputs via the data buffer unit to said speech decoding means formats Communication unit device being characterized in that a section. A fixed telephone interface unit that is provided between a public telephone network and a fixed telephone station connected thereto and used to input and output an analog voice signal to the fixed telephone station, and through the fixed telephone interface unit and voice encryption means to encrypt the digital audio signal is digitally converted input Te, and speech decoding means corresponding to the voice encryption unit, the voice encryption encrypted by means synchronization format voice encryption A data buffer unit for temporarily storing encrypted data, and converting the synchronous voice encrypted data stored in the data buffer unit into an asynchronous voice data signal and outputting the converted data via the public telephone network the voice data signals of the asynchronous format is input into a synchronous format of the audio encoded data Te, be output to the speech decoding means via said data buffer unit A format conversion unit, the front SL asynchronous format output from the format conversion unit audio data signal by analog modulation output to the public telephone network, analog modulation signal of the original input via the public telephone network A communication unit device comprising: an asynchronous modem for returning to an asynchronous audio data signal and outputting the same to the format converter . It is between public telephone plurality of which are terminated to network subscriber line and connected to the private branch exchange to, provided at a predetermined subscriber line is used, connected before Symbol predetermined subscriber to the private branch exchange a private branch exchange interface unit that inputs and outputs analog audio signals to an extension telephone station selected Shah lines, voice encryption to encrypt digital audio signal inputted digitally converted through the private branch exchange interface unit and means, speech decoding means corresponding to the voice encryption unit, a data buffer unit for temporarily storing the audio encrypted data encrypted synchronization format by the voice encryption unit, to the data buffer unit while the accumulated voice encrypted data of the synchronous format were then converted to an asynchronous format of the audio data signal output, the audio of the asynchronous type which is input through the public telephone network Converts the data signal to the synchronous format of the audio encoded data, and a format conversion unit via the data buffer unit for outputting to the audio decoding means, the audio before SL asynchronous format output from the format conversion unit data signals in analog modulation and output to the public telephone network, and an asynchronous modem output to the format conversion unit back to the audio data signal in the original asynchronous format analog modulated signal inputted through the public telephone network A communication unit device comprising: Communication unit according to any one of claims 3 to 6, characterized in that employing the encryption method suitable for the channel quality of the public telephone network.

Images