JPH03297276A - Facsimile equipment - Google Patents

Abstract

PURPOSE:To prevent interception with only a function of a reception station side by connecting a noise generating means to a line at the reception of picture information, connecting a filter of its own station to the line and receiving the picture information via the filter. CONSTITUTION:After the reception of a signal from a transmission station is discriminated, whether or not training is implemented in an excellent way is discriminated. When the training is successful, a CFR is sent. A 1st switching means 8 is opened, a filter 7 is connected between a MODEM 6 and a line, a 2nd switching means 9 is closed and a noise generating circuit means 10 is connected to a line terminal of the filter 7, the noise generating circuit means 10 is activated, from which a prescribed noise signal is outputted. The picture information is received and whether or not RTC is received is discriminated. When the reception of the picture information is finished, the start of the noise generating circuit means 10 is stopped and the 2nd switching means 9 is deenergized and the noise generating circuit means 10 is disconnected from the line.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a facsimile machine, and in particular,
The present invention relates to a facsimile device that can prevent eavesdropping using only a function on the receiving station side.

(Prior Art) Various techniques for preventing eavesdropping on facsimile machines have been proposed in the past, as disclosed in, for example, Japanese Patent Publication No. 18371/1983.

A facsimile machine with such an eavesdropping prevention function is
As shown in FIG. 11, the transmitting station (Tx) side facsimile machine 101A is equipped with an encryption device 105A, and the receiving station (Rx) side facsimile machine 101B is equipped with a decoding device 1.
Equipped with 05B.

Then, the facsimile device 101A uses an encrypting device 105A to encrypt the image information according to a predetermined procedure and transmits the encrypted image information, and the facsimile device 101B uses a decoding device 105B to encrypt the image information and transmit it using the reverse procedure. decipher it and output it as a hard copy.

Here, the same device (encryption/decryption device) can be used as the encryption device 105A and the decryption device 105B.

In this way, if the image information is encrypted and transmitted, even if the image information is intercepted, leakage of the image information can be prevented unless it is decrypted.

In addition, in addition to preparing multiple types of encryption methods, the transmitting station and the receiving station should agree in advance on which method to use for encryption, so that a third party can decrypt the encryption. Facsimile machines have also been proposed that are configured to make this even more difficult.

(Problems to be Solved by the Invention) The above-described conventional technology had the following problems.

In other words, the conventional facsimile machines mentioned above employ a technology that encrypts and transmits image information in order to prevent eavesdropping, but with this method, both the sending and receiving stations It is necessary to install the above-mentioned encryption/decryption device in the device, and as a result, eavesdropping prevention communication cannot be performed unless, for example, the same manufacturer and model are used as the transmitting station and the receiving station.

In addition, with facsimile machines that are equipped with multiple encryption methods, unless the sending and receiving stations decide in advance which method to use for encryption, the receiving station will be able to decode the encryption. can't do it.

The present invention has been made in order to solve the above-mentioned problems, and as shown in FIG. An object of the present invention is to provide a facsimile device that can perform eavesdropping-preventing communication by simply installing a device 106 for preventing eavesdropping only on the facsimile device 102 on the receiving station side.

(Means and effects for solving the problem) In order to solve the above-mentioned problems, the present invention provides a method for transmitting a signal (noise) of a predetermined frequency from the receiving station side while image information is being transmitted from the transmitting station side. The feature is that the image information is output to a line, and the receiving station receives the image information through a filter that removes noise at the output frequency. As a result, noise is superimposed on the image information on the line, but this noise is removed at the receiving station.

Another feature is that it can output noise of multiple types of frequencies. As a result, it becomes possible to selectively output noise of multiple types of frequencies onto the line.

Another feature is that the frequency of the noise is changed in a predetermined order or randomly at least for each communication, or each time a predetermined image information is received, such as for each page or line. .

Another feature is that the volume of the noise can be adjusted.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of a first embodiment of the invention.

In FIG. 2, a scanner 1, a printer 2, and an image memory 4 are connected to a control device 3. This control device 3 includes, for example, a microcomputer,
Control the facsimile device. This control device 3 is
As shown, an encoding/decoding device 5, a modem 6,
and is connected to a line (for example, a public line) via a filter 7. The filter 7 is for removing noise outputted and generated by a noise generation means 10, which will be described later, and cuts a signal having a frequency substantially the same as the frequency of the noise generated by the noise generation means 10. That is, in this embodiment, filter 7 is a bandpass filter.

The first switching means 8 has normally closed contacts;
The line side of the filter and the modem 6 side are connected so as to be short-circuited. This first switching means 8 is opened by a control signal output from the control device 3, and connects the filter 7 between the modem 6 and the line.

The noise generating means 10 generates a signal (noise) having the following frequency, for example. In other words, when using a public line as a line, the frequency band that the line can propagate is approximately 30~
It is approximately 3.3k [Hz], of which the frequency band normally used by facsimile machines is approximately 600 to 2400 [HZ].
z]. The noise generating means 10 generates a signal in a frequency band that is not often used by facsimile machines among the frequency bands of public telephone lines, that is, for example, about 30 to 30.
600 [Hz] or approximately 2400 to 3.3k [Hz]
Generate a signal at a specific frequency within the range of . This signal is output to the line and becomes noise.

The noise generating means 10 includes a second noise generator having a normally open contact.
It is connected to the line side terminal of the filter through the switching means 9.

The noise generating means 10 is activated by a control signal output from the control device 3. Further, the second switching means 9 is closed by the control signal, and connects the output signal line of the noise generating means 10 to the line side terminal (input terminal) of the filter.

The operation of this first embodiment will be explained with reference to FIG.

FIG. 3 is a flowchart showing the operation of the first embodiment of the present invention. Note that this flowchart shows the operation on the receiving station side, and the operation on the transmitting station is the same as the normal one.

First, after it is determined in step S1 that a signal from a transmitting station has been received, it is determined in step S2 whether training has been successfully performed. After successful training, the CFR is sent out in step S3.

Subsequently, in step S4, the first switching means 8 is energized and opened, and the filter 7 is connected between the modem 6 and the line.

In step S5, the second switching means 9 is energized and closed, and the noise generating means 10 is connected to the line side terminal of the filter.

Then, in step S6, the noise generating means 10 is activated (activated) and noise of a predetermined frequency is output onto the line.

In step S7, the image information (PIX) is received, and in step S8, it is determined whether the reception of the image information has ended, that is, whether the RTC indicating the end of the image information has been received. .

When the reception of the image information is completed, the activation of the noise generating means 10 is stopped in step S9, the energization of the second switching means 9 is stopped in step SIO, and
The noise generating means 1o is disconnected from the line.

In step Sll, the energization of the first switching means 8 is released, and the modem 6 side and line side terminals of the filter are short-circuited. That is, the filter 7 is disconnected from the facsimile machine.

The processing in steps S9 to Sll is completed after the reception of the image information is completed until the exchange of a predetermined protocol is executed. In FIG. 3, the step of sending and receiving this protocol is omitted. And step S
The received image information is decoded in step S12 and printed in step S13, after which the process ends.

Although not shown in FIG. 3, the received image information is stored in the image memory 4 as necessary.

In this way, when receiving image information, the noise generating means 10
By connecting to the line and activating it, the signal on the line (
Noise at the frequency is superimposed on the image information (image information output from the transmitting station). Therefore, even if the signal on the line is intercepted, it will be impossible to decipher the image information. However, since the image information is received through the filter 7 in the receiving station facsimile device, the noise is cut out, and normal image information can be received without being affected by the noise.

In addition, no noise is output on the line when exchanging protocols (exchanging control signals) before and after receiving image information.
The control signal is accurately transmitted to the receiving station without any omissions.

FIG. 1 is a functional block diagram of a first embodiment of the present invention. In FIG. 1, the same reference numerals as in FIG. 2 refer to the same or equivalent parts, so the explanation thereof will be omitted.

In FIG. 1, a communication control means 12 exchanges a predetermined protocol with a transmitting station and controls communication of the facsimile machine.

The image information reception determination means 13 determines whether or not image information is actually transmitted from the transmitting station, and whether or not the transmission of image information is completed. In detail, the image information reception determining means 1
Step 3 determines whether the transmitting station has outputted the CFR, and also determines whether the transmitting station has outputted the RTC indicating the end of the image information.

When the image information reception determining means 13 detects the CFR, it energizes the first switching means 8, the second switching means 9, and the noise generating means 10 to connect the filter 7 to the communication line and the communication control means 12 and the image information. The noise generating means 10 is connected to the line as well as the reception determining means 13. Then, the noise generating means 10 is activated.

Further, when the image information reception determining means 13 detects RTC, it stops energizing the first switching means 8, the second switching means 9, and the noise generating means 10, and disconnects the filter 7 and the noise generating means 10. At the same time, the activation of the noise generating means 10 is stopped.

FIG. 4 is a block diagram of a second embodiment of the invention. In FIG. 4, the same reference numerals as in FIG. 2 represent the same or equivalent parts.

In FIG. 4, the noise generating means 10A to 10D have frequencies of 300.500.2500 and 2700 [Hz], respectively.
Outputs noise. This noise generating means 10A to IO
D is connected to the line via second switching means 9A-9D, each having a normally open contact. Of course, the noise output from the noise generating means 10A to IOD may have frequencies other than those described above.

Filters 78 to 7D are each 300.500.25
Cuts noise of 00 and 2700 [Hz]. The filters 7A to 7D are connected in parallel through third switching means 21A to 21D having normally open contacts, respectively.
It is connected between the modem 6 and the line.

The first switching means 8 having normally closed contacts connects the filters 7A to 7D and the third switching means 21A to 2
Connected in parallel with 1D.

The control device 3 opens the first switching means 8 every time communication is performed, for example. Further, the control device 3 controls the noise generating means 10A to IO every time communication is performed and, if necessary, every time image information is transmitted page by page.
At the same time as activating the noise generating means 1 in sequence,
Second switching means 9A to 9 corresponding to 0A to 10D
D is closed, and the energized noise generating means 10A~
Filter 7A cuts noise output from 10D
The predetermined third switching means 21A to 21D are closed so that the third switching means 21A to 7D are connected to the modem 6.

The operation of this second embodiment will be explained with reference to FIG.

FIG. 5 is a flowchart showing the operation of the second embodiment of the present invention. Note that this flowchart, like FIG. 3, shows the operation of the receiving station, and the operation of the transmitting station is the same as the normal one.

Further, in FIG. 5, the same reference numerals as in FIG. 3 represent the same or equivalent processing.

After it is determined in step S2 whether the training has been performed satisfactorily, a count value N of a counter (not shown) in the control device 3 (FIG. 2) is incremented in step S21. This counter is assumed to sequentially output numerical values from θ to 3 by the increment described above.

After this, the CFR is sent out in step S3.

Next, in step S22, one of the filters 7A to 7D is connected to the modem 6 based on the relationship between N and frequency shown in FIG. be done. That is, the first switching means 8 is opened and the third switching means 2 is opened.
The modem 6 is connected to any one of the filters 7A to 7D which control the filters 1A to 21D and cut a predetermined noise.

In step S23, the noise generating means 10A to 10D that generate a signal with a frequency corresponding to N are connected to the line by controlling the second switching means 9A to 9D.

In step S24, any one of the connected noise generating means 10A to IOD is activated.

Then, in step S7, reception of image information is started.

If it is confirmed in step S25 that the reception of one page's worth of image information has been completed, then in step 826 any one of the activated noise generating means 10A to IOD is stopped.

In step S27, the second switching means 9A
~9D, any of the stopped noise generating means 10A~IOD is disconnected from the line.

In step 528, the connected filter 7
8 to 7D are disconnected from the modem 6. That is, the first switching means 8 is closed, and at the same time,
Any one of the third switching means 21A to 21D, which had been closed, is now opened.

In step S29, whether there are any remaining pages or not,
That is, it is determined whether or not the page is a multi-page page. If it is a multi-page, N is incremented in step S30, and the process returns to step S22.

If it is not multi-page, the received image information is decoded in step S12, printed in step S13, and then the process ends.

FIG. 7 is a functional block diagram of a second embodiment of the present invention. In FIG. 7, the same symbols as in FIGS. 1 and 4 are
The same or equivalent parts are shown.

In FIG. 7, if it is determined that the CFR is output from the transmitting station (that is, if it is determined that the transmission of image information is actually started), the image information reception determining means 13 starts the counter. 22, the first switching means 8 is opened, and when the reception of the image information is completed, the first switching means 8 is closed.

The counter 22 is energized by the CFH discrimination signal output from the image information reception discrimination means 13, outputs the count value N to the frequency table 23, and stops the output in response to the image information reception end signal. Further, the count value N is incremented each time the page discriminating means 24 detects that the reception of image information for each page has ended.

The frequency table 23 is a table as shown in FIG.

The count value N of the counter 22 is outputted via the frequency table 23, so that the noise generating means (10A
~IOD) is activated, and the activated noise generating means is connected to the line by closing the second switching means (any of 9A to 9D). Further, when one of the third switching means 21A to 21D is selected, a filter (any one of 7A to 7D) for cutting noise at a frequency corresponding to the N is placed between the line and the communication control means 12. be done.

In this embodiment, even if a third party were to eavesdrop on the communication and find out the frequency of the noise using some method, each time image information is received, one piece of image information is received. Since the frequency of the noise is changed every time the image is displayed, the risk of leakage of image information is low.

In this embodiment, the noise frequency is changed each time image information is received, or each time one piece of image information is received, but the noise frequency is changed each time image information is received, or It goes without saying that the noise frequency may be changed only every time one piece of image information is received.

Furthermore, one page may be divided into predetermined blocks, and the noise frequency may be changed for each block or for each line (main scanning line).

In addition, although it has been explained that the number of filters is equal to the number of noise generating means, as mentioned above, the frequency of the noise generated by the noise generating means is near the upper limit and lower limit of the audio frequency band, which is not often used for facsimile communication. If the noise is in a nearby frequency band, a low-pass filter that passes frequencies below the lowest frequency of noise near the upper limit of the audio frequency band, and a low-pass filter that passes frequencies above the highest frequency of noise near the lower limit of the audio frequency band. By using a pass-through bypass filter, only two types of filters can remove all the noise generated by the facsimile machine.

FIG. 8 is a functional block diagram of a third embodiment of the present invention. In FIG. 8, the same reference numerals as in FIG. 7 represent the same or equivalent parts.

This third embodiment is a modification of the second embodiment.

As is clear from the comparison between Figures 7 and 8, this third
In this embodiment, a random number generating means 25 is provided in place of the counter 22. This random number generating means 25 generates a
Each time reception of image information for each page is detected, θ~3
Generate random numbers.

Even in such a configuration, the frequency of the noise is changed each time image information is received or each time one piece of image information is received.

Note that when providing multiple types of noise generating means and filters, the configuration is not limited to those shown in FIGS. You may choose freely.

FIG. 9 is a functional block diagram of a fourth embodiment of the present invention. In FIG. 9, the same reference numerals as in FIG. 1 represent the same or equivalent parts.

As is clear from the comparison with FIG. 1, this embodiment is the same as the first embodiment except that a volume adjustment means 26 is provided. This volume adjustment means 26 outputs an output from the noise generating means 10 depending on the position where the eavesdropping device is installed, that is, the position on the line where eavesdropping is being performed, or the situation of the line. This is for adjusting the volume of the noise being played.

In other words, for example, if the line distance between the transmitting station and the eavesdropping device is short, and conversely the line distance between the receiving station and the eavesdropping device is long, the receiving station may output noise onto the line. As a result of the noise being attenuated before reaching the eavesdropping device, it may not be possible to affect the eavesdropping device to the extent that it disturbs the image information.

Of course, in order to receive image information accurately at the receiving station,
It is better to keep the volume of the noise as low as possible, within a range that does not affect the eavesdropping device and that can be cut by the receiving station's filter, but if the eavesdropping device is located in the above-mentioned position. If it is known, operate the volume adjustment means 26 to adjust the volume of the noise, and output the noise on the line to a level that makes it impossible for eavesdropping devices to receive the image information. be able to.

The volume adjusting means 26 may be a knob, dial, etc., which adjusts the volume in an analog manner by mechanical operation, or may be a soft switch, etc., which can be specified and operated from an operation panel.

The fourth embodiment is different from the first embodiment in that a volume adjustment means 26 is provided, but the volume adjustment means 26 may be provided in the second or third embodiment. good.

FIG. 10 is a functional block diagram of a fifth embodiment of the present invention. In FIG. 10, the same reference numerals as in FIG. 9 represent the same or equivalent parts.

As is clear from the comparison with FIG. 9, this embodiment is the same as the fourth embodiment except that noise detection means 27 and control means 28 are added.

Image information received via the filter 7 is input to the noise detection means 27, and noise in this data is detected.

The control means 28 controls the noise output from the noise generation means 10 to be maximized within a range in which the noise contained in the image information received via the filter 7 becomes almost zero. , the volume adjustment means 26 is feedback-controlled using the output signal of the noise detection means 27.

In this example, even if the characteristics of the filter 7 and the noise generating means 10 change over time, the noise is always generated at maximum volume without affecting the image information received by the receiving station. It can be output.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) According to the facsimile apparatus according to the first aspect, although noise is superimposed on the image information on the line, this noise is removed at the receiving station. Therefore, even if the image information is intercepted, accurate reproduction of the image information will not be possible.

In other words, the function of preventing wiretapping is achieved solely by the function of the receiving station.

(2) According to the facsimile device according to claim 2, it is possible to selectively output noise of multiple types of frequencies onto the line, so even if only one type of noise frequency is leaked to a third party. Even if you do so, it is unlikely that all image information will be reproduced correctly.

(3) According to the facsimile apparatus according to claims 3 and 4, at least once per communication or per page,
The noise frequency is automatically changed each time a predetermined image information is received, such as for each line, so even if only one type or all of the noise frequencies are leaked to a third party,
It is unlikely that all image information will be reproduced correctly.

(4) According to the facsimile apparatus according to claim 5, the volume of the noise can be adjusted depending on the connection position of the eavesdropping device on the line or according to the line condition. Even if the distance between the wires is far, noise can affect eavesdropping devices. That is, by increasing the volume of the noise, it is possible to output noise of a sufficient volume to the eavesdropping device so as to make accurate reproduction of image information impossible.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of a first embodiment of the present invention. FIG. 2 is a block diagram of a first embodiment of the invention. FIG. 3 is a flowchart showing the operation of the first embodiment of the present invention. FIG. 4 is a block diagram of a second embodiment of the invention. FIG. 5 is a flowchart showing the operation of the second embodiment of the present invention. FIG. 6 is a chart showing the relationship between the count value N and the frequency of the output noise. FIG. 7 is a functional block diagram of a second embodiment of the present invention. FIG. 8 is a functional block diagram of a third embodiment of the present invention. FIG. 9 is a functional block diagram of a fourth embodiment of the present invention. FIG. 10 is a functional block diagram of a fifth embodiment of the present invention. FIG. 11 is a schematic diagram showing a facsimile communication system provided with a wiretapping prevention function. FIG. 12 is a schematic diagram showing a facsimile communication system with a wiretapping prevention function according to the present invention. 3...Control device, 7,7A-7D...Filter, 8
. . . first switching means, 9, 9A to 9D . . . second switching means, 10. IOA~IOD... Noise generating means, 13... Image information reception determining means, 21A~
21D...Third switching means, 22...Counter, 23...Frequency table, 24...Page discrimination means, 25...Random number generation means, 26...Volume adjustment means, 27... Noise detection means, 28... control means,
102... receiving station side facsimile machine, 103...
Transmitting station side facsimile device, 10δ...device for preventing eavesdropping

Claims (5)

[Claims] (1) a noise generating means for outputting noise of a predetermined frequency; a filter for removing the noise; energizing the noise generating means to output the noise to the line when image information is received; and reception control means for connecting the filter to a line and receiving image information via the filter. (2) The facsimile machine according to claim 1, wherein the noise generating means outputs noise of a plurality of types of frequencies, and the reception control means selectively outputs the noise of a plurality of types of frequencies to the line. Device. (3) At least for each communication, or for each reception of predetermined image information such as each page, each line, etc.
3. The facsimile apparatus according to claim 2, further comprising a counter whose count value is incremented, and wherein said reception control means outputs noise at a frequency corresponding to said count value to a line. (4) At least for each communication, or for each reception of predetermined image information such as each page, each line, etc.
3. The facsimile apparatus according to claim 2, further comprising random number generation means for generating random numbers, and wherein said reception control means outputs noise at a frequency corresponding to said random number to a line. (5) The facsimile apparatus according to any one of claims 1 to 4, further comprising a volume adjusting means for adjusting the volume of the noise output by the noise generating means.