JPH0394535A - Analog privacy telephone set - Google Patents

Abstract

PURPOSE:To preclude the possible of interception and to prevent loss of privacy even when same equipments are in branch connection by setting a signal pattern outputted from a noise signal generating circuit with a multi-frequency signal. CONSTITUTION:A multi-frequency signal inputted to a sender side input terminal 11 of a privacy telephone set 1 is subject to calculation processing in an arithmetic circuit AU 17, converted into a signal representing an address of a memory M 16 and the signal setting an initial value of a shift register is outputted to a transmission noise generating circuit NG 12 and a reference noise generating circuit NS 19. A multi-frequency signal receiver RC 35 of a privacy telephone set 2 sends a signal to an arithmetic circuit AU 37 and converted into a signal representing an address of a memory M 36. According to the address signal, the initial value of the same shift register as that in the transmission noise generating circuit NG 12 of the privacy telephone set 1 is set to a reference noise generating circuit NS 39.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an analog secret communication device, and in particular, on the transmitting side, the transmitted voice signal is combined with a noise signal whose power spectrum is approximately flat within the entire frequency band of the transmitted voice signal. The analog secret speech device is configured to transmit a secret speech signal with a superimposed signal, extract an audio signal from the received secret speech signal on the receiving side, and set a signal pattern output from a noise signal generation circuit using a multi-frequency signal. Regarding.

[Conventional technology]

Conventionally, this type of analog confidential communication device had the configuration shown in Figure 2. FIG. 2 is a block diagram showing an example of a conventional analog secret communication device, in which a secret communication device 5, a secret communication device 6, and a transmission line 80 are occluded. In the secret device 5, 51 is a transmitting side input terminal for inputting a transmission audio signal to the secret device 5, 52 is a transmitting noise generating circuit that periodically generates noise with the same waveform, and 53 is a terminal from the transmitting side input terminal 51. 54 is a switch that determines the initial values of the shift registers of the transmission noise generation circuit 52 and the reference noise generation circuit 56;
5 is a hybrid circuit, 56 is a reference noise generation circuit, 57
58 and 59 are adaptive echo cancellers that use the signals from the transmission noise generation circuit 52 and the reference noise generation circuit 56 as reference signals, respectively, and 60 is a transmission line input/output terminal. The configuration of the privacy device 6 shown in the figure is also the same as that of the privacy device 5, and 61 is a transmitting side input terminal, 62 is a transmission noise generation circuit, 63 is an addition circuit, 64 is a switch,
65 is a hybrid circuit, 66 is a reference noise generation circuit, 6
7 is a receiving side output terminal, 68 and 69 are adaptive echo cancellers, and 70 is a transmission line input/output terminal. Next, the operation of this example will be explained.

First, the operation of sending a voice signal from the secret device 5 to the secret device 6 will be explained.

An adder circuit 53 adds a transmission noise signal from a transmission noise generation circuit 52 to the audio signal input to the transmission side input terminal 51. At this time, the signal output from the adder circuit 53 becomes a confidential signal and is output to the transmission input/output terminal 60. The confidential communication signal outputted to the transmission line input/output terminal 6o is transmitted to the confidential communication device 6 via the transmission path 80. In the privacy device 6, the privacy signal is input to the transmission line input/output terminal 70 and output to the adaptive echo canceller 69 via the hybrid circuit 65.

However, since the transmission noise signal from the transmission noise generation circuit 62 is also input to the hybrid circuit 65 in addition to the audio signal input to the transmission side input terminal 70 of the privacy device 6, the adaptive echo canceller 6'9 does not contain the privacy device. The secret signal of No. 5 and the secret signal of the secret device 6 are input. Therefore, first, the adaptive echo canceller 69 removes the transmission noise signal from the privacy device 5 by referring to the reference noise signal from the reference noise generation circuit 66 which has the same function as the transmission noise generation circuit 52 of the privacy device 5. ．． Next, the adaptive echo canceller 68
With reference to the transmission noise from the transmission noise generation circuit 62 of the privacy device 6, the transmission noise signal from the privacy device 6 is removed. And these adaptive echo cancellers68.6
9 reproduces the audio signal from the confidential communication device 5 and outputs it from the reception side output terminal 67 of the confidential communication device 6.

The operation from the secret device 6 to the secret device 5 is exactly the same. Here, the transmission noise generation circuit and the reference noise generation circuit are a maximum long period series (M series) with a period of 2fi-1, which is obtained by giving feedback from a binary adder to an n-stage feedback shift register. ) is a circuit that generates pseudo-random number pulses called pulses. That is, by giving certain initial values to each stage of the shift register, several types of noise signal patterns can be obtained. Conventionally, both users of this device agreed in advance to set this initial value using a switch, and the same pattern of pulses were generated from the transmission noise generation circuit and the reference noise generation circuit.

[Problem to be solved by the invention]

In the conventional analog confidential communication device described above, in order to generate the same pattern of pseudo-random pulses from the transmission noise generation circuit and the reference noise generation circuit, both the users of this device have to switch the initial value setting, so there is no need for the user to manually set the initial value. This has the disadvantage that it is troublesome and easy to make mistakes during setting. Furthermore, if you try to configure switch settings during a call, you will have to communicate the switch settings in words, and if the same device is connected to a branch, there is a risk of it being intercepted and confidentiality is lacking. was there.

[Means to solve the problem]

The analog confidential communication device of the present invention sends a confidential signal obtained by adding a noise signal to a voice signal on the transmitting side to a two-wire transmission line via a hybrid circuit, and transmits the confidential signal obtained by adding a noise signal to a voice signal on the receiving side. a first adaptive echo canceller for extracting the voice signal from the confidential signal received through the transmission noise generating circuit; In an analog secret speech device that uses a part of the echo canceller to cancel the secret speech by a second adaptive echo canceller, the multifrequency signal receiver includes a multifrequency signal receiver, a memory into which initial value data of a shift register is input, and the multifrequency signal an arithmetic circuit that converts a signal output from a receiver into address information and outputs an initial value of the shift register by referring to data in the memory; the shift register of the transmission noise generation circuit and the reference noise generation circuit; The feature is that the initial value of is set at multiple frequencies. [Example] Next, the present invention will be explained with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the analog secret communication device of the present invention.

First, the analog confidential communication device system of this embodiment includes a confidential communication device 1, a confidential communication device 2, a general subscriber telephone T3, a general subscriber telephone T4, and a transmission line 30. In the secret device 1, 11 is a transmitting side input terminal for inputting a transmission audio signal to the secret device 1, 12 is a transmitting noise generating circuit NG that periodically generates noise with the same waveform, and 13 is a terminal from the transmitting side input terminal 11. 14 is an adder circuit AD that adds the audio signal and the noise signal from the transmission M sound generation circuit NG12 and outputs a secret signal; 14 is a switch SW that connects the addition circuit AD13 and the transmission noise generation circuit NGI2; RC, 16 is the transmission noise generation circuit NG12 and the base*noise generation circuit NS19.
The memory M, 17 stores data for setting the initial value of the shift register of the multi-frequency signal receiver RC15, and the arithmetic circuit AU, 18.17 receives the signal from the multi-frequency signal receiver RC15, performs arithmetic processing, compares it with the memory M16, and outputs the signal. 25 is a hybrid circuit H, 19 is a reference noise generation circuit NS, 20 (4 switch SW, 21 is a reception side output terminal of the secret device 1, 22.23
are adaptive echo cancellers EC which use signals from the transmission noise generation circuit NG 1 2 and the reference noise generation circuit NS19 as reference signals, respectively, and 24 is a transmission line input/output terminal. The structure of the confidential communication device 2 in the figure is also the same as that of the confidential communication device 1,
31 is a transmission side input terminal, 32 is a transmission noise generation circuit NG,
33. 40 is a switch SW, 34 is an adder circuit AU, 35
is a multi-frequency signal receiver RC, 36 is a memory M, 37 is an arithmetic circuit AU, 38.45 is a hybrid circuit H, 39 is a reference noise generation circuit NS, 41 is a receiving side output terminal, 42.4
3 is an adaptive echo canceller EC, and 44 is a transmission line input/output terminal.

Next, the operation of this embodiment will be explained.

First, the operation of sending an audio signal from the confidential communication device 1 to the confidential communication device 2 will be explained.

The transmission noise signal from the transmission noise generation circuit NG12 is added to the audio signal input to the transmission side input terminal 11 by the addition circuit AD13. At this time, the signal output from the adder circuit ADI3 becomes a confidential signal and is output to the transmission input/output terminal 24. Transmission line input/output terminal 24 {The output secret signal is transmitted to transmission line 3
0 to the secret device 2. In the confidential communication device 2, the confidential communication signal is inputted to the transmission line input/output terminal 44, and is sent to the adaptive echo canceller EC4 via the hybrid circuit H38.
3 is output. However, since the transmission noise signal from the transmission noise generation circuit NG32 is also input to the hybrid circuit H38 in addition to the audio signal input to the transmission side input terminal 44 of the encrypting device 2, the adaptive echo canceller EC43 receives the audio signal input from the transmitting side input terminal 44 of the encrypting device 2. A secret signal and a secret signal from the secret device 2 are input. Therefore, first, the adaptive echo canceller EC43 removes the transmission noise signal from the privacy device 1 by referring to the reference noise signal from the reference noise generation circuit NS39, which has the same function as the transmission noise generation circuit NG12 of the privacy device 1. ．． Next, the adaptive echo canceller EC42 refers to the transmission noise from the transmission noise generation circuit NG32 of the privacy device 2 and removes the transmission noise signal from the privacy device 2.

And these adaptive echo cancellers EC42.43
According to Secret Information W. The audio signal from 1 is reproduced and output from the receiving side output terminal 4l of the confidential communication device 2. The operation from secret device 2 to secret device 1 is exactly the same. Next, the operation of sending a multi-frequency signal from the general subscriber telephone T3 to the general subscriber telephone T4 will be explained.

A multi-frequency signal input to the transmission side input terminal 11 of the confidential communication device 1 is input to the multi-frequency signal receiver RC15. A signal is sent from the multi-frequency signal receiver RC15 to the arithmetic circuit AU17, arithmetic processing is performed in the arithmetic circuit AU17, and the signal is sent to the memory M'l.
Convert to a signal representing address 6. In accordance with the address signal, the input data is sent out from the memory M16, passes through the arithmetic circuit AU17, and outputs a signal for setting the initial value of the shift register to the transmission noise generation circuit NG12 and the reference noise generation circuit NS19. At this time, the multi-frequency signal is also output to switch SW14.20, and switch SW14.
14. Turn on 20. The multi-frequency signal is output to the transmission line input/output terminal 24 via the hybrid circuit H18. The multi-frequency signal output to the transmission line input/output terminal 24 is transferred to the transmission line 3.
0 to the secret device 2. In the confidential communication device 2, the multifrequency signal is inputted to the transmission line input/output terminal 44, and then inputted to the multifrequency signal receiver RC35. Multi-frequency signal receiver R
A signal is sent from C35 to the arithmetic circuit AU37, and the arithmetic circuit A
Arithmetic processing is performed in U37 and converted into a signal representing the address of memory M36. In accordance with the address signal, the memory M36 sends out the input data, and sends a signal to the reference noise generation circuit NS39 to set the initial value of the same shift register as the transmission noise generation circuit NG12 of the security device 1. Noise generating circuit NG32 transmits the initial value of the same shift register as reference noise generating circuit NS19 of No.1.
A signal to set the value is output from the arithmetic circuit AU37. Also, at this time, a multi-frequency signal is output to switch SW34.40 to turn on switch SW34.40. The operation from general subscriber telephone 4 to general subscriber telephone 3 is exactly the same.

〔Effect of the invention〕

As explained above, according to the present invention, the transmitting side sends out a secret signal in which the transmitted audio signal is superimposed on a noise signal whose power spectrum is approximately flat within the entire frequency band of the transmitted audio signal, and the receiving side By extracting the audio signal from the received confidential signal and setting the signal pattern to be output from the noise signal generation circuit using a multi-frequency signal, it is possible to avoid erroneous settings without bothering the device user. Also, when trying to configure the switch during a call, there is no need to communicate the switch setting status verbally, so even if the same device is connected in a branch, there is no risk of it being intercepted, and confidentiality is improved. It has the effect of not being damaged. 17.37... Arithmetic circuit (AU), 18, 25, 38
,45,55.65...Hybrid circuit (H), 1
9,39,56.66...Reference noise generation circuit (NS)
, 21, 31, 57.67... receiving side output terminal, 22
, 23, 42, 43, 58, 59,
68. 69...Adaptive echo canceller (EC
), 24.44, 60.70...transmission line input/output terminal,
30.80...Transmission line.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an analog secret communication device of the present invention, and FIG. 2 is a block diagram showing an example of a conventional analog secret communication device.

Claims (1)

[Claims] On the transmitting side, a confidential signal obtained by adding a noise signal to the voice signal is sent to a two-wire transmission line via a hybrid circuit, and on the receiving side, the confidential signal obtained by adding the noise signal to the voice signal is transmitted through the hybrid circuit. The first step is to extract the audio signal.
A second adaptive echo canceller uses a part of the signal of the transmitting noise generating circuit to eliminate leakage to the receiving circuit by passing the transmitting noise signal through a hybrid circuit. The analog secret communication device to be removed includes a multi-frequency signal receiver, a memory into which the initial value data of the shift register is input, and a memory that converts the signal output from the multi-frequency signal receiver into address information. an arithmetic circuit that outputs an initial value of the shift register by referring to data of the analog signal generator, and sets the initial values of the shift registers of the transmission noise generation circuit and the reference noise generation circuit at multiple frequencies. Confidential device.