JPH03216038A - Privacy call equipment - Google Patents

Abstract

PURPOSE:To ensure synchronization in an excellent way at the start of communication and to attain proper privacy communication by sending a tone signal of a consecutive time decided in response to a processing start delay time at a receiver side prior to the synchronizing signal. CONSTITUTION:A privacy call transmitter-receiver 10 is provided with a microphone 12, a speaker 14, a privacy equipment 16 and a transmission/reception section 18. In this case, a tone signal of a single tone in a short time succeeding to a nonvoice prior to the transmission of a superframe is sent at the start of transmission. The consecutive time of the nonvoice period of the tone signal is set corresponding to the processing start delay time of a privacy equipment at the receiver side. Thus, even when a processing start delay time exists in the receiver side privacy equipment, the synchronizing signal is not lost at the receiver side due to the preceding transmission of the tone signal and normal reception of the synchronizing signal is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a secure communication device, and particularly to a device for performing temporal order scrambling on audio signals.

[Prior Art] Conventionally, methods such as the TSP method have been known as methods for keeping communication contents secret in FM transceiver systems and the like.

This method is a method in which the captured audio is encoded, and the temporal order of the encoded audio is changed before being transmitted and received. This replacement is generally called scrambling, and conversely, the process of descrambling is called descrambling.

That is, the transmitting side device scrambles the temporal order of the audio signal according to a predetermined rule, and wirelessly transmits the scrambled signal as a confidential audio frame to the receiving side. On the receiving side, this confidential voice frame is received, and the scramble processing performed on the received signal on the transmitting side is canceled (descrambled). As a result, the audio captured on the transmitting side is played back on the receiving side, making it impossible for others to intercept it. In other words, confidential communication becomes possible.

In addition, the rules regarding scrambling and descrambling are as follows:
It is set in advance on the sending and receiving side devices. Furthermore, a rolling code method is also adopted in which this rule is changed as necessary.

When performing confidential communication using the TSP method, it is necessary to synchronize both transmitting and receiving devices. For this reason, the transmitting side device issues a synchronization signal at regular intervals to supply synchronization timing to the receiving side. That is, when a predetermined number of confidential speech frames are to be transmitted, a synchronization signal that can be clearly distinguished from the confidential speech frames is generated prior to the transmission. The synchronization signal and a predetermined number of confidential voice frames that are successively transmitted are collectively called a superframe.

Therefore, at the start of transmission, a synchronization signal is first issued, and the receiving side detects the transmission timing of the confidential voice frame.

[Problems to be Solved by the Invention] However, in the past, if there is some kind of processing start delay time on the receiving side, the synchronization signal cannot be processed normally and confidential communication becomes impossible. there were.

For example, ■ If there is a squelch delay on the receiving side, ■ If a specific device is selected from multiple receiving devices using a code to receive reception, ■ If an intermittent reception method is adopted, etc. Ten msec, several hundred msec, several hundred mS
A processing start delay time of the order of eC to several SeC occurs.

Furthermore, depending on the device configuration, a combination of these delay times may also occur.

If such a processing start delay time occurs, even if a synchronization signal is issued at the start of communication, the receiving side cannot start normal processing, so the synchronization signal cannot be processed normally.

The present invention has been made to solve such problems, and it is an object of the present invention to provide a confidential communication device that can normally receive a synchronization signal despite a delay in the start of processing on the receiving side. .

[Means for Solving the Problems] In order to achieve the above object, the privacy device of the present invention is configured such that, at the start of transmission, prior to sending out a superframe, the privacy device on the receiving side is set in accordance with the processing start delay time of the security device on the receiving side. The present invention is characterized by comprising tone sending means for sending out a tone signal continuously for a period of time.

The secret speech device of the present invention includes tone detection means for outputting a tone signal from an input signal, and descrambling start means for turning on the power to the descrambling means and starting its operation in response to the detection of the tone signal by the tone detection means. It is characterized by

Here, it is preferable that the duration of the tone signal is variably set.

[Function] In the confidential communication device according to claim (1) of the present invention, at the start of transmission, prior to sending out a super frame, silence is followed by a very short period of time (about several milliseconds) of a single tone (single tone (2 kHz)). ) tone signal is sent out.

The duration of the silent period of the tone signal is set in accordance with the processing start delay time of the private communication device on the receiving side. Therefore, even if there is a processing start delay time in the confidential communication device on the receiving side, the synchronization signal will not be lost on the receiving side by sending out the tone signal in advance.

In the secret speech device according to claim (2) of the present invention, a single tone in the last period of the tone signal is further detected from the input signal, and descrambling is started in response to this.

In the private conversation device according to claim (3) of the present invention, the duration of the tone signal is variably set here.

[Examples] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

Configuration of Embodiment FIG. 1 shows the configuration of a confidential communication system employing a confidential communication transmitter/receiver according to an embodiment of the present invention.

The system in this figure is an FM transceiver system that uses the TSP method, and has multiple (two in the figure) transceiver systems.
It is composed of a confidential transmitter/receiver 10.

The confidential communication transmitter/receiver 10 includes a microphone 12 and a speaker 1.
4. Contains a secret device 16 and a transmitting/receiving section 18. Furthermore, in this figure, both secret communication devices 16-1 and 1
6-2 shows a key writer 20 that is connected as necessary.

FIG. 2 shows the circuit configuration of the confidential communication device 16.

In this figure, the microphone 12 is connected to the amplifier 22,
It is connected to the human power of a coder/decoder 28 via switches 24 and 26.

In addition, a switch 30 is connected to the input of the coder/decoder 280.
, an amplifier 32 and a switch 26 to a receiving circuit (not shown) of the transmitting/receiving section 18 .

The output of the coder/decoder 28 is connected to the switches 34, 36,
It is connected to a transmitting circuit (not shown) of the transmitting/receiving section 18 via an amplifier 38 and an ATT 40.

On the other hand, the output of this coder/decoder 28 is connected to the speaker 14 via a switch 34, an AGC 42, a switch 44, and a volume 46.

Switches 24 and 36, Switches 30 and 44, Switch 2
6 and 34 are interlocking switches.

When the switches 24 and 36 are turned upward in the figure,
The microphone 12 and the transmitting circuit of the transmitting/receiving section 18 are short-circuited without going through the coder/decoder 28. Similarly,
When the switches 30 and 44 are turned upward in the figure,
The receiving circuit of the transmitting/receiving unit 18 and the speaker 14 are short-circuited without going through the coder/decoder 28. In these cases,
No confidential communication takes place.

When switches 26 and 34 are turned to the upper side (T side) in the figure,
The microphone 12 is connected to the human power of the coder/decoder 28, and the transmitting circuit of the transmitting/receiving section 18 is connected to the output thereof. In this case, audio input from the microphone 12 is supplied to the transmitting circuit of the transmitting/receiving section 18 via the coder/decoder 28 . Conversely, when the switches 26 and 34 are turned to the lower side (R side) in the figure, the receiving circuit of the transmitter/receiver 18 is connected to the input of the coder/decoder 28, and the speaker 14 is connected to the output of the coder/decoder 28.
are connected to each other. In this case, the transmitting/receiving unit l8
The signal received by the receiving circuit is output as audio from the speaker 14 via the coder/decoder 28.

Coder/decoder 28 is connected to data bus 50 via I/048, which performs serial/parallel conversion. A CPU 52 and a RAM 56 of approximately 32 kB backed up by a battery 54 are also connected to the data path 50 .

Coder/decoder 28 is further connected to a synchronization detection circuit 58. A RAM 60 of approximately 4 kB is connected to the synchronization detection circuit 58.

An EPROM 62 of about 8 kB is connected to the data bus 50.

On the other hand, an audio signal detection circuit 62 is connected to the receiving circuit of the transmitting/receiving section 18.
2 is an erroneous synchronization prevention circuit 64 via a power supply hold circuit 63.
It is connected to the. A synchronization detection circuit 58 is also connected to this erroneous synchronization prevention circuit 64 .

A joint timing generation circuit 66 is connected to the false synchronization prevention circuit 64 . This link timing generation circuit 66 is connected to the AGC 42.

In addition, Datahas50 also includes PTT68 and ■/070
A PTT switch 72 is connected via. Also,
The key writer 2 is connected to the data path 50 via the I/O 70.
0 is also connected as necessary.

Frame structure of this embodiment Next, the frame structure of this embodiment will be explained.

FIG. 3 shows the frame structure in this embodiment.

The voice captured by the microphone 12 is converted into, for example, 8-bit PCM data il, i2, . . . in a coder/decoder 28.

Furthermore, this PCM data il, i2, . . .
When collected, one segment is constructed.

In the figure, the segments are designated SO, Sl, . . . .

One frame is composed of eight segments SO, Sl, . . . S7.

Furthermore, by collecting 46 frames Fl, F2, . . . F46 and adding a chirp signal to the beginning, super frames SFI, SF2, . A chirp signal is a signal whose frequency changes, for example, linearly within a certain interval, and is used as a synchronization signal between the transmitting side and the receiving side in this embodiment. Note that there is a silent period between the chirp signal and frame F1.

For example, PCM data il, i2,... is 125 μS
If it is sent out in eC, the segments Sl, S2, −
．． ．． is 3 2ms e c, frame Fl, F2,
... is 256 msec. Chirp signal is 192
msec and the following silent time is 64ms e c, then superframes SFI, SF2,... are 12
0 3 2 msec.

The rules regarding scrambling and descrambling are as follows:
For example, the following method is used.

(1) 8 segments SO in one frame
, SL, S2, . . . , S7 are changed in accordance with a predetermined rule.

(2) PCM data i within one segment
1, i2, i3, . . . , i256 is reversed for a particular selected segment.

(3) PCM data il, i2. i3,...
invert the sign bit of for a particular selected segment.

If you scramble according to these rules, you will end up with a frame Fl that cannot be played unless you know the scrambling rules.
, F2, . . . will be generated.

Furthermore, in this embodiment, a tone signal according to the feature of the present invention is transmitted prior to the first superframe SFI.

The tone signal is a signal of silence followed by a single tone for an extremely short period of time (several milliseconds), and is a signal that continues for a time Tt initially set by the key writer 20.

The duration time Tt of the tone signal is set to, for example, about 128 msec.

Operation of this embodiment The operation of this embodiment will be explained for each operating state shown in FIG.

FIG. 4 is a transition diagram of operating states in this embodiment.

First, immediately after the confidential communication transmitter/receiver 10 starts operating, the confidential communication device 16 is in a standby state 100. In this state 100, the confidential communication transmitter/receiver 10 is not making any wireless output, and no carrier wave is being transmitted.

When the PTT switch 72 is pressed from this state 100, the state shifts to the transmission state 200.

When a tone signal arrives from another transceiver in the standby state 100, the privacy device 16 detects this and shifts to the reception state 300.

That is, audio is transmitted and received while pressing the PTT switch 72 as necessary.

In this embodiment, it is necessary to perform scrambling and descrambling according to the rules described above. This scrambling and descrambling rule is the key manual condition 4
00 is entered manually as a key code.

Further, in this embodiment, the duration of the tone signal according to the feature of the present invention is also set as the key code.

The operation will be described below only when the switches 24, 30, 36, and 44 are turned down in the figure. When the switches 24, 30, 36, and 44 are tilted upward in the figure, confidential communication is not performed, so a description thereof will be omitted here.

(1) Operation in standby state 100 In this embodiment,
The transmitter/receiver 18 employs a so-called intermittent reception method. That is, in a state where no transmission or reception is performed (standby state 100 and key manual state 400), carrier waves related to transmission and reception are not transmitted. Furthermore, the secret communication device 16 employs a so-called standby system. That is, in the standby state 100, the audio signal detection circuit 6
No power is supplied except for 2 and PTT68. This method is adopted to reduce power consumption.

(2) Operation in Transmission State 200 Transmission by the device of the embodiment is started by the caller pressing the PTT switch 72.

When the PTT switch 72 is pressed, the PTT 68 turns on the power to the privacy device 16 and sends a PTT signal to the transmitting/receiving section 18, thereby entering the transmitting state. Furthermore, the CPU 52 learns that the PTT switch 72 has been pressed via the I/O 70 and data path 50, and at 1/048, the coder/decoder 2
8 to the transmitting circuit of the transmitting/receiving section 18. Silence is followed by a single tone signal for an extremely short period of time (several milliseconds).

After tone signal transmission is completed, first, a Chubb wave is transmitted. Here, it is assumed that the switches 26 and 34 have been turned to the T side in advance in response to the depression of the PTT switch 72.

For this transmission, the waveform stored in the EFROM 62 is encoded by the coder/decoder 28, and the switches 34, 36,
This is done by sending the signal to the transmitting/receiving section 18 via the amplifier 38 and the ATT 40.

Following the chirp signal, there is a predetermined period of silence, and then a scrambled audio signal is transmitted.

First, audio captured from the microphone 12 is input to the coder/decoder 28 via the amplifier 22 and switches 24 and 26.

The coder/decoder 28 encodes the input audio signal into 8-bit PCM data il, i2, .

The encoded PCM data il, i2, . . .
048 to the data path 50.

PCM data il, i2 . on data bus 50 . . . are taken into the CPU 52 and scrambled based on rules stored in the RAM 56 (for example, the sending order of segments SO, SL, . . . ).

Note that since the RAM 56 is backed up by the battery 54, such rules are saved even when the device is powered off.

The scrambled PCM data il, i2, .

Scrambled PCM data il i2,...
After transmitting one super frame, the chirp signal is transmitted again, and PCM data transmission is continued.

(3) Operation in reception state 300 When a tone signal arrives from another transceiver 10, this tone signal is detected by the audio signal detection circuit 62. When the audio signal detection circuit 62 detects a single note in the last period of the tone signal, a signal indicating the arrival of the tone signal is issued to the power supply hold circuit 63.

The power hold circuit 63 indicates that the device is in standby state 1 immediately before
00, the circuit power is turned on in response to the detection of the arrival of the tone signal. A signal indicating the arrival of the tone signal is also supplied to a false synchronization prevention circuit 58.

In addition, depending on the arrival of the tone signal, the switches 26 and 3
4 is pushed to the R side.

The tone signal is continuously supplied for the time stored in the transmitting side RAM 513, and then the chirp signal is supplied. As will be explained in detail later, the duration of the tone signal is set according to the time required for processing start delay time on the receiving side.

The chirp signal is input to coder/decoder 28 via switch 30, amplifier 32, and switch 26. The coder/decoder 28 encodes the chirp signal and converts it into 8-bit PCM data 11, 12, . . .
g to the data path 50.

On the other hand, the output from the coder/decoder 28, namely P
The most significant bits of the CM data il, i2, . . . are supplied to the synchronization detection circuit 58. This most significant bit is
This is a bit representing the sign of M data, that is, a polarity bit.

The polarity bits are stored in the RAM 60 for a predetermined period of time, and the polarity bits of the addresses corresponding to the sample points that have a high correlation with the chirb signal are read out, and the degree of correlation is determined based on the number of polarity bits, either positive or negative. That is,
The synchronization detection circuit 58 detects whether the signal has arrived from the transmitting side or the chirp signal based on the polarity bit.

When the synchronization detection circuit 58 detects the arrival of the chirp signal, the synchronization detection circuit 58 sends the signal to the CPU 5 2 via the erroneous synchronization prevention circuit 64 and I/048.
A synchronization detection signal is sent to The synchronization detection signal is also supplied to a joint timing generation circuit 66, which suppresses the gain of the AGC 42 in order to suppress joint noise peculiar to scrambling processing. If the arriving signal is not a synchronization signal but a noise similar to a chirp signal, the false synchronization prevention circuit 64
The synchronization detection signal becomes invalid.

Upon receiving the synchronization detection signal, the CPU 52 starts descrambling at a predetermined timing based on the rules stored in the RAM 56. Note that the rules stored in the RAM 56 need to be the same rules as the rules stored in the RAM 56 on the sending side.

The PCM data to be descrambled is supplied from the receiving circuit of the transmitting/receiving section 18 following the chirp signal with a silent period in between. That is, when a chirp signal arrives, there is silence for a predetermined period, and then an audio signal related to communication arrives. This audio signal is input to a coder/decoder 28.

Furthermore, the data bus 5 is encoded and transmitted via I/048.
Sent to 0. The CPU 52 takes this in and descrambles it. After descrambling, further I/
048, coder/decoder 28, switch 34, AGC
42, a switch 44, and a volume 46, the audio is output from the speaker.

A receiving operation is performed by repeating such an operation.

(4) The explanation of the operations in the transmission state 200 and the reception state 300 above the operation in the key manual state 400 is based on the premise that the rules for scrambling and descrambling and the duration of the tone signal are set in advance in the RAM 56. This is an explanation.

The rules for scrambling and descrambling and the duration of the tone signal are stored in RAM56 in the key manual state 400.
is set to

First, the key writer 20 is connected to the I/O 70. When a predetermined key code is output from the key writer 20, for example as a serial key code, this key code is
/O 70 and data path 50 to RAM 56.

This key code includes a code representing the scrambling/descrambling rule as described above and a code representing the duration of the tone signal.

The code representing the scrambling/descrambling rule is a code obtained by being selected by the caller as necessary from among a number of selectable encryption keys, for example, about 7×1019, and being encoded using, for example, a non-linear encoding method.

Further, the code representing the duration of the tone signal is determined according to the processing start delay time due to squelch delay on the receiving side.

These key codes are simultaneously written into the RAM 56 by, for example, the same key writer 20.

Alternatively, the parties on the transmitting side and the receiving side may share the encryption key with each other and write it in separate key writers 20.

[Effects of the Invention] As explained above, according to the present invention, a tone signal with a duration determined according to the processing start delay time on the receiving side is sent out prior to the synchronization signal, so that the tone signal on the receiving side The synchronization signal is never lost. therefore,
It becomes possible to ensure good synchronization at the start of communication and perform suitable confidential communication.

Further, according to the present invention, descrambling is started in response to the arrival of a tone signal, so that synchronization signals are not lost and, for example, a standby system can be adopted.

In the present invention, since the duration of the tone signal is further variably set, the above-mentioned effects can be obtained even when the receiving side is changed to another device.

[Brief explanation of drawings]

1 is a system configuration diagram showing the configuration of a confidential communication system employing a confidential communication device according to an embodiment of the present invention; FIG. 2 is a circuit diagram showing the configuration of a confidential communication system according to the present embodiment; The figure is a frame configuration diagram in this embodiment, and FIG. 4 is an operation state transition diagram in this embodiment. 1 0 ... 1 6 ... 1 8 ... 2 0 ... 2 8 ... 5 2 ... 5 6 ... 6 2 ... 63 ... 2 0 0 ... 3 0 0 ... Transmitter/receiver confidential communication device Transmitter/receiver section Key writer coder/decoder CPU RAM Audio signal detection circuit Power supply hold circuit Transmission state Reception state 400 ... Key power state Fl, F2, ..., F46 ... Frame SFI
SF2,..., SF46... Super frame

Claims (2)

[Claims] (1) A scrambling unit that generates a confidential audio frame by scrambling processing that changes the temporal order of audio signals according to a predetermined rule, and an audio output that sends out a superframe that includes a plurality of the confidential audio frames and has a synchronization signal added to the beginning. a transmission confidential speech unit including means; a synchronization signal detection means for detecting a synchronization signal from an input signal; and when the synchronization signal is detected, the input signal is regarded as the super frame and the confidential speech frame is synchronously extracted; descrambling means for reproducing an audio signal by canceling the scrambling process for the extracted confidential audio frame;
and a reception secretion unit including: At the start of transmission, prior to sending out the superframe,
1. A confidential communication device comprising tone sending means for continuously transmitting a tone signal for a time set corresponding to a processing start delay time of a receiving side confidential communication device. (2) The confidential communication device according to claim (1), further comprising tone detection means for detecting a tone signal from the input signal, and powering on the descrambling means in response to the detection of the tone signal by the tone detection means; A secret communication device comprising a descrambling start means for starting an operation. (3) The secret communication device according to claim (1), wherein the duration of the tone signal is variably set.