CN201995006U - Encryption device for telephone set - Google Patents

Abstract

The utility model discloses a telephone encryption device, which is composed of two frequency inverters with a split point, a password selection circuit, a state control circuit, a telephone host, an earpiece, and a microphone, and one frequency inverter is set as a transmission mode. It is connected in series between the microphone and the main phone to realize the frequency conversion encryption function; the other is set in the receiving mode and connected in series between the handset and the main phone to realize the frequency conversion decryption function; the switch of the password selection circuit is connected with the frequency inverter A0 -A4 terminal connection, select the split point to determine the encryption scheme; the output of the state control circuit is connected to the C/S and LATCH terminals of the frequency inverter, providing encryption or non-encryption working mode control. It solves the disadvantages of low security and easy decryption of the conventional voice modulation encryption method, and overcomes the disadvantage of complex structure and high cost of digital encryption technology.

Description

A telephone encryption device

technical field

The utility model discloses a telephone encryptor, which belongs to the technical field of telephone communication security.

Background technique

The continuous development and popularization of communication technology has brought more and more convenience to people's work and life. But at the same time, it also brings some troubles to people. For example, incidents of personal information being stolen continue to occur, and some even constitute serious cases. Ways of information theft include misappropriation of personal documents, misappropriation of network information and misappropriation of telephone information.

In order to prevent the telephone from being tapped and ensure the information security in the telephone communication, various telephone encryption devices have been produced one after another. The device designed for this purpose has anti-tapping detector at present, when finding to monitor the phone and send an alarm when it is connected on the telephone set. There are voice changers, which change the pitch of the speaker's voice, making it higher or lower, distorting the voice overheard in the middle and making it inaudible. At the other end of the communication, there is a corresponding device to restore the changed tone, so that the speech can be heard clearly. There is also a voice encryptor using digital technology, which converts the analog voice signal into a digital signal, and then compresses and encodes the voice signal in digital form to achieve the purpose of encryption. The encrypted voice signal is then modulated into an audio signal at a certain rate so that it can be transmitted in an analog system.

Although the speech tone changer is simple in structure, low in cost, and has a certain degree of secrecy, its degree of secrecy is extremely low. The tone and intonation information are completely preserved in the tone-modified voice signal, and experienced listeners can basically judge the tone of the speech. content. On the contrary, although the speech scrambler utilizing digital technology has quite high confidentiality, its structure is complicated, the cost is extremely high, and there is also a large time delay. In addition, from the perspective of application scope, the voice changer is not strictly an encryptor, it can only simply cover up the voice. Essentially, it only changes the sound quality, which can be restored with a simple device. Therefore it can only be applied in some unimportant occasions. Due to the high security and high cost characteristics of the voice encryptor using digital technology, it is generally used in independent communication systems with high security, such as military communication systems.

Contents of the invention

The utility model discloses a telephone encryption device, which not only solves the disadvantages of low security and easy decryption of conventional voice modulation encryption methods, but also overcomes the disadvantages of complex structure and high cost of digital encryption technology, and has the advantages of simple structure, safety and practicality, Strong confidentiality and relatively cheap cost.

The technical solution that the utility model is used for telephone encryption method is as follows:

A frequency inverter with a split point is connected in series between the microphone of the telephone, the handset, and the main unit of the telephone, and the voice signals spoken by the microphone are frequency converted and encrypted, and then sent through the main unit of the telephone, and the encrypted voice received by the handset is The signal undergoes the same frequency transformation to complete the decryption process. The state control circuit and the password selection circuit are respectively connected with two frequency inverters to realize the state transition control and determine the selected password scheme;

The frequency inverter with the split point is to select a frequency point in the audio range, namely the split point fs, to split the frequency band of the entire audio frequency into two sub-bands of the low frequency band of 300-fsHz and the high frequency band of fs-3300Hz; Then use the above-mentioned frequency inverter to perform inverse transformation on the spectrum of the two sub-bands, that is, move the lower frequency to the higher frequency band in each sub-band, and move the higher frequency to the lower frequency band. frequency band. The spectrum conversion process and results of this frequency converter are shown in Figure 1.

In the frequency inverter of the split point, the split point can also be adjusted.

The telephone encryption device realizing the method of the utility model is characterized in that: it is composed of two frequency inverters with split points, a password selection circuit, a state control circuit, a telephone host, an earpiece, and a microphone. A frequency inverter is set in the transmission mode, and is connected in series between the microphone and the telephone host to realize the encryption function. The other is set in the receiving mode, and is connected in series between the handset and the telephone host to realize the decryption function. The password selection circuit is connected with the frequency inverter, and the split point is selected to determine the encryption scheme. The state control circuit is connected with the frequency inverter to provide encryption or non-encryption working mode control and other necessary auxiliary control signals.

The frequency inverter selects the integrated circuit MX224, which is a frequency inverter with a variable split point used in wireless communication voice encryption. It has good voice recovery quality, fixed and hopping coding methods, 32 programmable split points, half-duplex operation mode and other characteristics; it uses two MX224, one is running in the sending state, and the other is running in the In the receiving state, the full-duplex design is completed, and the receiving and sending of telephone communication are realized at the same time. The working principle of the system is shown in Figure 2.

When the telephone is working normally, the microphone on the handle and the handset signal are connected to the corresponding terminals on the main unit of the telephone to form a voice path. Disconnect the handle of the motor from the host, and insert the encryption device of the utility model in the middle. When talking, the microphone on the handle of the telephone generates a voice signal. The MX224 converts the frequency of the voice, that is, encrypts the signal, and then sends the encrypted signal back to the microphone terminal of the phone host; when answering, the encrypted voice comes out of the receiver terminal of the phone host, not directly sent to the receiver terminal on the handle , but sent to the MX224 working in the receiving state for frequency conversion, that is, after decryption processing, the original intelligible voice signal is restored, and then output to the earpiece terminal on the handle.

The function of the password selection circuit is to select different encryption schemes for the encryption device, that is, when encrypting and decrypting, the password selection circuit selects different split points for the MX224. MX224 has a total of 5 data input lines from A0 to A4. By inputting different logic levels, one of the 32 split points can be selected arbitrarily, which is equivalent to selecting one of the 32 encryption schemes. This device adopts a relatively simple fixed password scheme. The password selection circuit is mainly composed of a dial switch, and its function is to provide an appropriate logic level for the five-digit data lines from A0 to A4.

The state control circuit provides encryption state and non-encrypted normal state transition control for the encryption device. MX224 has a C/S terminal, the high level is the encrypted state, and the low level is the unencrypted straight-through state. However, the control levels sent to A0-A4 and C/S become valid only after another latch signal is input. The state control circuit consists of two button switches on the right, a NAND gate integrated circuit and some resistance and capacitance components. The specific functions of this circuit include: (1) Provide anti-shake and locking functions for the switch, because the button switch itself cannot be locked, it will be turned on when it is pressed, and it will be automatically turned off when it is not pressed. It is guaranteed that a high level or a low level is provided for the MX224 when different switches are pressed respectively. (2) Provide a power-on reset function for the encryption device, that is, ensure that the system is initially in an unencrypted working state when the power is turned on, and there is no need to press the corresponding switch. (3) When the system is powered on or any switch is pressed, a latch signal is provided.

In addition, this device has a power supply circuit that provides a positive 5V voltage for the entire system, and its operating current is 5mA. The input of the power circuit is +9V DC voltage.

The connection between the telephone voice encryption device and the telephone is accomplished through two 4-pin sockets, one of which is connected to the telephone host, and the other is connected to the handle. There are 8 signal lines: the microphone signal line, microphone ground line, handset signal line, and handset ground line from the telephone before encryption and decryption; the microphone signal line, microphone ground line, and handset signal line leading to the handle after encryption and decryption , handset ground.

The positive effect of the utility model lies in that: what is adopted is the encryption method of performing frequency domain transformation on the voice signal, and is analog signal processing instead of digital signal processing, so the voice encryption processing process has no delay. It solves the disadvantages of low security and easy decryption of the conventional voice modulation encryption method, and overcomes the disadvantage of complex structure and high cost of digital encryption technology.

Description of drawings

Fig. 1 is the process and the result schematic diagram of spectrum conversion of the present utility model;

Fig. 2 is a circuit diagram of the utility model;

Fig. 3 is the schematic circuit diagram of the utility model.

Detailed ways

Example 1

As shown in Figure 2, when talking, the sound signal from the microphone is sent to the TxIN pin of the MX224 in the sending state to convert the frequency of the voice, and the encrypted signal is output through TxOUT, and then sent back to the microphone terminal of the phone host. When answering, the encrypted voice comes out from the handset terminal of the main body of the telephone, and is sent to the RxIN pin of the MX224 in the receiving state. After decryption, it is output to the handset terminal on the handle through the RxOUT pin. The password selection circuit is mainly composed of a five-digit dial switch, which is connected to two MX224s. Its function is to provide an appropriate logic level for the five-digit data lines from A0 to A4, and determine the selected password scheme. The state control circuit is connected to the C/S terminals of two MX224, the high level is the encrypted state, and the low level is the unencrypted state, to realize the state transition control.

Example 2

As shown in Figure 3, the password selection circuit is 5 switches. A0-A4 of the MX224 have internal pull-up resistors, which are high when the switch is open and low when the switch is closed. Use the 5-bit DIP switch to realize the function of manually setting the password.

The state control circuit uses two NAND gates to connect to form an R-S flip-flop, and its R input terminal is grounded through a button switch and a capacitor in parallel, and the S terminal is grounded through the other. This flip-flop is low level triggered. If the switch connected to R is pressed, the trigger output terminal Q will be sent to the C/S terminals of the two MX224s at a high level, and it will be set to an unencrypted state. The flip-flop still maintains a high level output after the switch is turned off. On the contrary, when the switch connected to S is pressed, the trigger output terminal Q will be sent to the C/S terminals of the two MX224s at a low level, and it will be set to an encrypted state. Likewise, the flip-flop remains in the low-level output state after the switch is turned off. The capacitor connected in parallel with the switch on the R terminal of the trigger realizes the function of automatic reset after power-on. The voltage across the capacitor is zero before energization. According to the property that the voltage on the capacitor cannot jump, the voltage can only gradually increase from zero after energization. This is equivalent to pressing the switch every time the power is turned on to reset the system to an unencrypted state. In addition, the two input ends of a NAND gate are respectively connected to two switches. When the switch is not pressed, the output of the NAND gate is low level, and when any switch is pressed, the output is high level. The output goes low again. In this way, whenever a switch is activated or a power-on reset is performed, a "low-high-low" logic sequence is provided for the LATCH terminals of the two MX224s, which is exactly what is needed to latch the data.

Test example 1

After debugging the encryption device of Example 1, experiments were carried out, and all functions and indicators met the expected design requirements.

Before connecting with the telephone set, first set the 5-digit dial switches of the encryption devices of both communication parties to the same state, that is, select the same password. Then connect the dongles of the communication parties to the telephone according to the following sequence and method: (1) Unplug the connecting line plug of the phone handle at the main phone side; (2) Insert the unplugged plug into the encryption on the corresponding socket of the device. (3) Insert one end of a connecting line with two plugs into the socket where the handle connecting line has just been unplugged on the main phone side, and insert the other end into the corresponding socket of the dongle. (4) Connect the DC output plug of the 9V regulated power supply to the power socket of the dongle, and connect the AC plug to the 220V mains.

When making an outgoing call, take off the handset and dial the called number normally. After connecting, if you need encryption, press the encryption button switch, if you don't need encryption, you don't need to do anything, just talk directly. If you press the encryption key by mistake, you can press the normal button switch again. In the encrypted state, the red indicator light is on. During normal communication, the green indicator light is on. When answering the phone, if you don’t need encryption to speak directly, you need to encrypt and press the encryption button switch. Regardless of dialing or receiving, the device is always in an unencrypted normal state after it is powered on.

The call experiment was done under three conditions: no encryption on both sides, both encryption and one encryption and the other unencryption. When both parties use the non-encrypted working mode of the encryptor, the call effect is basically the same as that of only using the telephone, and there is no difference in sound quality and volume. When both sides use the encryption working method of the encryptor, the volume basically does not change, and the sound quality sounds rich in bass, but without distortion. And when one party uses the encryption method and the other party uses the non-encryption method, although both parties can hear the sound, they cannot hear the sound of language, let alone judge the meaning of the language. Experimental results prove that the design of this telephone voice encryption device is successful, and the application of this device on telephones is feasible. At the same time, it also proves the stability of its work and the simplicity of operation.

Claims (1)

1. A telephone encryption device is characterized in that: it is composed of two frequency inverters with split points, a password selection circuit, a state control circuit, a telephone host, an earpiece, and a microphone, and a frequency inverter is set to send One mode is connected in series between the microphone and the main phone to realize the frequency conversion encryption function; the other is set in the receiving mode and connected in series between the handset and the main phone to realize the frequency conversion decryption function; the switch of the password selection circuit is reversed to the frequency The A0-A4 terminals of the frequency inverter are connected, and the split point is selected to determine the encryption scheme; the output of the state control circuit is connected with the C/S and LATCH terminals of the frequency inverter, and the encryption or non-encryption working mode control is provided.

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