JPH06321018A - Antitheft device of on-vehicle acoustic equipment - Google Patents

Abstract

PURPOSE:To prevent burglary through a process of making the protect release difficult, by providing such a structure as including a means for detecting a first mode reconnected after an acoustic equipment is separated from a main power supply, and discharging an inserted recording medium during the first mode. CONSTITUTION:An discrimination code of an acoustic device is registered in a memory 1, and the discrimination code and a cipher code input by a keyboard 1 are compared with each other in a CPU 3 when an acoustic equipment is reconnected to a power supply 5 after it is separated from the power supply 5. When both codes do not coincide with each other, the first mode (burglary mode) is detected by an operation limiting means of the CPU 3, so as to be displayed on a display unit 4. A PLL circuit 9 gives synchronous frequency control signals to a tuner unit 8 on the basis of the PLL voltage (b) from the CPU 3, but the signals from the tuner unit 8 or a deck unit 7 are shut off by a control signal (c) from the CPU 3 in the case of burglary mode. Thus, the recording medium inserted into the deck unit 7 is discharged during the burglary mode, and the synchronous frequency of the turner part 8 is fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft device, and more particularly to an anti-theft device for vehicle audio equipment.

[0002]

2. Description of the Related Art In recent years, most vehicles, especially passenger cars, are equipped with audio equipment. With the spread of high-priced on-vehicle audio equipment and high-performance audio equipment, there have been frequent thefts in which the owner of a car removes it and sells it without permission, or incorporates it into his car. Therefore, as one of these anti-theft measures, the on-vehicle audio equipment is once disconnected from the normal power supply (battery), and then reconnected to the normal power supply (in the case of theft, another car or another normal power supply). And unless the code stored in the memory of the device and the input code from the keyboard, etc., match the operation of the in-vehicle audio equipment with some restrictions, the stolen in-vehicle audio equipment cannot be used. There are things that try to prevent theft.

FIG. 6 shows a conventional example of the above-mentioned anti-theft device for vehicle-mounted audio equipment, and the memory 2 stores, for example, a 4-digit code. The power supply 64 of the CPU 3 is cut off (OF
F) is constantly monitored, and when the power is cut off and supplied again (ON), the "theft mode" (mode for protecting the audio equipment) is entered. "Theft mode"
Below, the CPU 3 turns off the relay 65 so that no current is supplied from the power supply to the device 67 side (66 is a power switch, 68 is a speaker). The "theft mode" cannot be canceled unless the same code as the code stored in the memory is input from the keyboard 1.

[0004]

In the above conventional example, the protection of the audio equipment depends on the conduction / non-conduction of the current by the relay 3 which is turned on / off by the CPU 3.
If the relay part of the stolen car audio equipment is short-circuited (for example, with a wire) and used, the car audio equipment itself can operate normally even in the "theft mode". It was

The present invention has been made in view of the above-mentioned drawbacks, and in an anti-theft device for an on-vehicle audio device using a personal identification code, a stolen on-vehicle audio device is stolen when in a "theft mode". It is an object of the present invention to provide an anti-theft device for vehicle-mounted audio equipment in which it is extremely difficult to remove the protection.

[0006]

In order to achieve the above object, an antitheft device for an on-vehicle audio equipment according to a first aspect of the invention comprises a storage means for storing an identification code, an input means for inputting a personal identification code, When the acoustic device has a comparison means for comparing the identification code with the identification code, and the audio equipment is separated from the main power supply and then connected to the main power supply again, when the identification code input by the input means does not match the identification code In an anti-theft device for an on-vehicle audio device equipped with an operation limiting means for limiting the operation of an audio device, the operation limiting means sets the first mode in which the audio device is separated from the main power source and then connected to the main power source again. A first mode detecting means for detecting, and a block for ejecting the recording medium inserted in the deck part of the audio device and fixing the tuning frequency of the tuner part of the audio device during the first mode. And having a stage, a.

According to a second aspect of the present invention, in the antitheft device for vehicle-mounted audio equipment according to the first aspect, the operation limiting means further comprises:
It is characterized by having a signal blocking means for blocking the demodulated signal from the tuner unit during the first mode.

According to a third aspect of the present invention, in the antitheft device for vehicle-mounted audio equipment according to the first or second aspect of the invention, further, during the first mode, the operation for limiting the audio equipment by the operation limiting means is the limiting operation means. The present invention is characterized by having a limiting action expressing means that indicates a limiting action.

An on-vehicle audio equipment anti-theft device according to a fourth aspect of the present invention comprises storage means for storing an identification code, input means for inputting a personal identification code, and comparison means for comparing the identification code and the personal identification code. On-vehicle equipped with operation limiting means for limiting the operation of the audio device when the identification code and the identification code input by the input means do not match when the audio device is disconnected from the main power supply and then connected to the main power supply again In the anti-theft device for audio equipment, the operation limiting means is
First mode detection means for detecting the first mode in which the audio device is separated from the main power source and then connected to the main power source again, and the sequence of the reproduction signal from the audio device is converted and output during the first mode. And a scramble processing unit for performing the scramble processing.

A fifth aspect of the present invention is the anti-theft device for vehicle-mounted audio equipment according to the fourth aspect of the present invention, further comprising:
The present invention is characterized by further comprising limiting operation expressing means for indicating that the limiting operation of the audio device by the operation limiting means is the limiting operation of the limiting operation means.

[0011]

In order to achieve the above object, in the anti-theft device for an on-vehicle audio equipment according to the first aspect of the invention, the operation limiting means is re-maintained after the audio equipment is separated from the main power source by the first mode detecting means. The first mode connected to the power source is detected, and during the first mode, the recording medium is always ejected even when inserted, and the tuning frequency of the tuner section is fixed.

According to a second aspect of the present invention, in the antitheft device for vehicle-mounted audio equipment according to the first aspect, the operation limiting means further comprises:
The signal blocking means blocks the demodulated signal from the tuner unit during the first mode.

According to a third aspect of the present invention, in the anti-theft device for vehicle-mounted audio equipment according to the first or second aspect of the invention, further, during the first mode, the operation of the audio equipment is restricted by the operation restricting means by the restriction operation expressing means. This is a limiting operation of the limiting operation means.

In the antitheft device for an on-vehicle audio equipment according to the fourth aspect of the present invention, the operation limiting means separates the audio equipment from the main power source by the first mode detecting means, and then connects the main mode again to the first mode. Is detected, the order of the reproduced signals from the tuner section is converted and scrambled for output during the first mode by the scramble processing means.

A fifth invention is the antitheft device for vehicle-mounted audio equipment according to the fourth invention, further comprising:
The limiting operation expressing means indicates that the limiting operation of the audio device by the operation limiting means is the limiting operation of the limiting operation means.

[0016]

【Example】

<Embodiment 1> FIG. 1 is a block diagram showing the configuration of an embodiment of an antitheft device for an on-vehicle audio device according to the present invention.
FIG. 2 is a flowchart showing the operation of the CPU as the control unit in the “theft mode” described later.

In FIG. 1, 1 is a keyboard as an input means for inputting a personal identification number, 2 is a memory in which the personal identification number is registered, 3 is a CPU for controlling the entire apparatus, and 4 is a display section. It corresponds to a limiting operation display means, 5 is a battery as a normal power source (first power source), 6 is a power switch of an in-vehicle audio device, and 7 is a desired medium for accommodating / driving a recording medium such as a cassette tape or CD A deck section for selecting music and reproducing an acoustic signal, 8 a tuner section for receiving a signal and selecting and demodulating a signal tuned to a predetermined frequency, and 9 a PLL (Phase Locked Loop) , A tuning frequency control signal output means, 10 is a mute circuit for temporarily cutting off a signal and corresponds to signal cutoff means, 11 is an amplifier, and + B is a backup power supply (second power supply). ), SW1, SW2 is a switch.

In FIG. 1, a vehicle power source 5 is a power switch 6
It is connected to the CPU 3 and the amplifier 11 via. Also, the backup power source + B is the CPU 3 and the switch SW.
1 to the deck section 7 or the tuner section 8 via the switch SW2.

The CPU 3 is connected to the keyboard 1, the memory 2, the display (display section) 4, the vehicle power source 5, the backup power source + B, the PLL circuit 9 and the mute circuit 10.
Further, SW1 and SW2 are connected by a control line. The keyboard 1 is used when inputting an identification code (personal code) of this vehicle audio device. An identification code of this vehicle audio device is registered in the memory 2, and is read out to obtain a match when a personal identification code is input from the keyboard 1.

When the antitheft device of the present invention operates and the audio device operates in a manner other than the normal operation, the display unit 4 indicates to the user of the audio device "theft mode" instead of the malfunction of the audio device.
It is used to inform that it is operating (described later). Therefore, the display unit 4 is not limited to a visual warning such as a display but may be a voice warning.

The deck section 7 is a mechanism for accommodating / driving a recording medium such as a cassette tape or a CD having a fixed sound, selecting a desired music and reproducing an acoustic signal, and also includes a mechanism for eliminating the recording medium. The tuner unit 8 receives a signal and receives a desired frequency (PL) when the audio device is used not as a sound reproducing device for a recording medium but as a receiving / reproducing device for a music program.
A signal to be tuned to the tuning frequency control signal from the L circuit 9) is selected and demodulated.

The PLL circuit 9 gives a tuning frequency control signal to the tuner section 8 based on the PLL voltage b from the CPU 3. The mute circuit 10 is the CPU when the "theft mode" is set.
The signal from the tuner section 8 or the deck section 9 is cut off by the control signal c from 3.

The operation of the antitheft device for an on-vehicle audio equipment according to the present invention will be described below with reference to FIG. Normally, when the on-vehicle audio device is removed from the vehicle, the vehicle battery 5 and the audio device are physically disconnected (or separated), and the power supply is not supplied to the audio device side.

As described above, in the present invention, the CPU 3 is connected to the vehicle battery 5 and the backup power source + B. Since the CPU 3 constantly monitors the supply of electric power from the vehicle battery 5, when the vehicle-mounted audio device is removed from the vehicle as described above (power off (OF
F)) is detected (S1). When the power is off, CPU3
The backup power source + B switch is turned on (ON) by the control of (S2).

When the switch of the backup power source + B is turned on (ON), the "theft mode" is set, and the other cases are set as the "normal mode".

The removed audio device for vehicle will eventually have a power source for use (third power source (usually different from the vehicle battery of the original vehicle, but may be the vehicle battery of the original vehicle (removed for repair, etc. If the power switch 6 is turned on))), the power switch 6 is turned on. However, since the CPU 3 is connected to the input power supply line as described above, it detects the power switch on state (S3).

When the power switch 6 is turned on, it is determined whether or not a personal identification code is input from the keyboard 1 (S
4). If the personal identification code is not input, S7 and subsequent steps ((a) and subsequent steps in the figure) are executed.

When the personal identification code is input, the identification code registered in the memory 2 is compared, and when the identification code does not match, the identification code input step of S4 is executed again. When the codes match, the operation of the audio device (recording / reproducing process, which is the normal operation (not the use by theft, but the use by the legitimate owner, the antitheft device of the present invention is not operated, that is, “normal mode”) Alternatively, the demodulation / reproduction process of the received program) is performed and the process ends.

When the power switch 6 is on and the personal identification code is not input from the keyboard 1, the control signal c
To turn on the mute circuit 10 (S2), and control the contacts of SW1 and SW2 by the control signals a and a'to the side of the deck section 7 (S8). The recording medium (cassette tape in the embodiment) is placed on the deck section 4. It is determined whether or not it is stored (S9). If the recording medium is not stored in the deck unit 4, steps S12 and thereafter are executed.

When the recording medium is housed in the deck section 4, the recording medium is discharged to disable the reproduction of the acoustic signal (S10), and SW1 and SW2 are controlled by the control signals a and a ', and the deck is controlled. The section 4 is turned off and the driving of the deck section 4 is stopped (S11).

The contacts of SW1 and SW2 are connected to the control signal a,
The tuner unit 8 is controlled by a '(S12).
However, in this case, even if a variable frequency switch (not shown) on the keyboard is operated, the PLL voltage is kept constant (variable prohibited) (S13). Then, it is determined whether or not the personal identification code is input from the keyboard 1 (S14).
When the secret code is input, the mute circuit 10 is turned on by the control signal c (S15), and in the figure (b) and below (S).
5 or less) is executed.

When the personal identification code is not input from the keyboard 1, it is judged whether or not the recording medium is inserted (S16), and if the recording medium is not inserted, S1.
Execute 2 or less.

When the recording medium is inserted, the tuner section 8 is turned off (S17) and the deck section 7 is turned on (S18). Then, although back loading is once performed (S19), immediately (C) is executed, so that the recording medium is ejected in S10, and the deck unit 4 is turned off and the driving is stopped in S11.

According to the above operation, in the present embodiment, all the recording medium in the deck portion 7 is ejected during the "theft mode", so that the audio signal from the recording medium cannot be read and reproduced. Further, since the demodulated signal from the tuner section 8 is cut off by the mute circuit 10, no sound is reproduced. Therefore, according to the present embodiment, a person who does not know the secret code (user of the stolen audio device) cannot substantially use the on-vehicle audio device incorporating the anti-theft device of the present invention. In addition, by making the display unit 4 notify the user that the unusable state in the "theft mode" is in the "theft mode" state, it is easy to distinguish it from the failure of the audio device, and the proper ownership A person can easily cancel the "theft mode" by inputting a personal identification code and use it as a normal audio device. Moreover, the antitheft device of the present invention does not use a relay, and releasing the recording medium removing operation by the deck section and the signal cutoff operation by the mute circuit in the "theft mode" can be performed only by releasing the "theft mode". It is impossible.

Therefore, the authorized owner can easily cancel the "theft mode" by inputting the personal identification code and use it as a normal audio device, but the person who does not know the personal identification code can use the "theft mode". It is extremely difficult to cancel (because it is almost impossible for an ordinary person to read the identification code registered in the memory, and even if all combinations of identification codes are entered, the number of digits in the code is lengthened. Or, if the code itself is a combination of alphanumeric characters, the number of combinations will be enormous even with a short number of digits, and it is extremely difficult to match the code except by chance).

<Embodiment 2> FIG. 3 is a block diagram showing the structure of another embodiment of an on-vehicle audio equipment antitheft device according to the present invention. FIG. 4 is an explanatory view of scrambling processing, and FIG. Is a CP as a control unit in "theft mode"
It is a flowchart which shows operation | movement of U.

In FIG. 3, components 1 to 11 are the same as those in the first embodiment (FIG. 1), and a description thereof will be omitted. Also,
41 is an A / D converter that converts an analog signal into a digital signal, 42 is a RAM (Random Access Memory), 4
Reference numeral 3 is a D / A converter for converting a digital signal into an analog signal, which constitutes a signal sequence conversion means.

The structural difference from the first embodiment is that the PL
It has no L circuit and mute circuit, and has an A / D converter 41, a RAM 42, and a D / A converter 43.

In FIG. 3, the vehicle power source 5 is a power switch 6
It is connected to the CPU 3 and the amplifier 11 via. Also, the backup power source + B is the CPU 3 and the switch SW.
The deck unit 7 is connected via 1 and the tuner unit 8 is connected via the switch SW2.

The CPU 3 is connected to the keyboard 1, the memory 2, the display (display section) 4, the vehicle power source 5, the backup power source + B and the RAM 42, and is also connected to SW1 and SW2 by the control lines a and a '. In the "theft mode", the CPU 3 apparently sends the read addresses to be sent to the RAM 42 in a random order. The keyboard 1 is an identification code (password code) of this vehicle audio device.
Used when inputting.

The identification code of the vehicle audio system is registered in the memory 2, and is read out for matching when the personal identification code is input from the keyboard 1. When the anti-theft device of the present invention operates and the audio device operates in a manner other than the normal operation, the display unit 4 operates in a "theft mode" (described later) instead of a malfunction of the audio device to the user of the audio device. It is used to indicate that you are

The deck section 7 is a mechanism for accommodating / driving a recording medium such as a cassette tape or a CD having a fixed sound, selecting a desired music and reproducing an audio signal, and also includes a mechanism for eliminating the recording medium. The tuner unit 8 receives a signal when the audio device is used not as a sound reproducing device for a recording medium but as a receiving / reproducing device for a music program, and selects and demodulates a signal tuned to a predetermined frequency.

In the D / A converter 41, the signal from the tuner section 8 or the deck section 9 is converted into a digital signal and R
Write to a predetermined address of AM42. In the RAM 42, in the "normal operation mode", the data is read again in the same order as the writing, but in the "theft mode", the data is read in the (apparent) random order by the scrambling process described later. This read mode change is controlled by the CPU 3.

The A / D converter 43 converts the digital signal read from the RAM 42 into an analog signal. Therefore, the signal that has passed through the A / D converter 41, the RAM 42, and the D / A converter 43 is output as a musically worthless unintended acoustic signal in the "theft mode".

The operation of the anti-theft device for vehicle-mounted audio equipment according to the present invention will be described below with reference to FIG.
The "theft mode" and the operations from S1 to S6 are described in the first embodiment.
2 is similar to the case of FIG. If the personal identification code is not input from the keyboard 1 when the power switch 6 is on, the contacts of SW1 and SW2 are controlled by the control signals a and a'to be the deck section 7 side (S7),
It is determined whether or not a recording medium (cassette tape in the embodiment) is stored in the deck section 4 (S8). Deck part 4
When the recording medium is not stored in S15, S15 and thereafter are executed.

When a recording medium is stored in the deck section 4, an acoustic signal is reproduced from the recording medium (S9),
The reproduction signal is scrambled by the RAM 42 via the A / D converter 41, converted into a signal, and output via the D / A converter (S10). In this case, the output signal is reproduced as a musical sound having no musical value.

Next, in order to switch the mode of the audio device to the tuner mode (refer to the usage mode of the audio device by receiving the broadcast program by the tuner section 8), S14 and the following steps are executed (S11). If not switched, it is determined whether or not a personal identification code is input from the keyboard 1 (S12). When the personal identification code is not input, the step of determining whether to switch the tuner mode in S11 is executed again (S12).

When the personal identification code is input, the memory 2
If the codes do not match with each other, the tuner mode switching judgment step of S11 is executed again (S13). If the codes match, the operation of the audio device according to the following normal operation (b) (S
6) is performed and the processing is ended.

The deck section 7 is turned off (S14). The tuner unit 8 is turned on (S15), the desired broadcast program is received, and the received signal is demodulated (S16). The demodulated signal is scrambled via the RAM 42 via the A / D converter 41, converted into a signal, and output via the D / A converter 43 (S17). The output signal in this case is S10.
Similarly, it is played as a musically meaningless sound.

Next, when the mode of the audio device is switched to the deck mode (which means the usage mode of the audio device by the reproduction of the recording medium by the deck section 7), (a) the following steps are executed (S18). When the mode is not switched to the deck mode, it is determined whether or not the personal identification code is input from the keyboard 1 (S19). When the secret code is not input, the steps of turning on the tuner unit 8 in S15 and the following steps are repeated (S20). If the personal identification code is input, it is compared with the identification code registered in the memory 2. If the codes do not match, the tuner unit 8 in S15 is again used.
Is repeated (S21), and when the codes match, the operation of the acoustic device according to the normal operation of (B) below (S6) is performed, and the process is ended.

<Scramble Processing> FIG. 4 is an explanatory diagram of the scramble processing. A signal from the tuner section 8 or the deck section 9 is converted into a digital signal by the A / D converter 41, but the order of read signals from the CPU in the "theft mode" is different from that in the "normal mode".

In FIG. 4A, the reproduction signal (digitalized by the A / D converter 41) data from the tuner section 8 or the deck section 9 is in the "normal mode" and the "theft mode" at the time of writing. Both are written in ascending order (or in descending order) of addresses as shown in FIG.

Further, during reading, the CPU 3 sends the read addresses in the order of the written addresses in the case of the "normal mode", so that the order of the write data and the read data is the same as shown in FIG. 4C. Therefore, the reproduced sound is reproduced in a normal state.

On the other hand, in the "theft mode", the CPU 3 determines the reading order of the storage addresses of the data by a random number based on a random function, unlike the order of the written addresses, and the read addresses are apparently in the random order. Since the data is transmitted, the order of the write data and the read data does not match as shown in FIG. Therefore, the reproduced sound is reproduced as a peculiar sound.

According to the above operation, in the present embodiment, during the "theft mode", the reproduced signals from the deck section 7 and the tuner section 8 are converted by scramble processing, and the voice signal is reproduced as a sound having no musical value.

Therefore, according to the present embodiment, a person who does not know the personal identification code (user of the stolen audio device) can actually use the vehicle audio device incorporating the anti-theft device of the present invention. I can't. In addition, by making the display unit 4 notify the user that the unusable state in the "theft mode" is the "theft mode", it is easy to distinguish it from the failure of the audio device, and the proper ownership A person can easily cancel the "theft mode" by inputting a personal identification code and use it as a normal audio device. On the other hand, it is extremely difficult for a person who does not know the personal identification code to cancel the “theft mode” (the reason is as described in the first embodiment and omitted).

[0057]

As described above, according to the first aspect of the present invention, all the recording medium in the deck portion is ejected during the "theft mode", so that the audio signal from the recording medium cannot be read and reproduced. Further, according to the second aspect of the invention, the demodulated signal from the tuner section is cut off, so that no sound is reproduced. Fourth
According to the invention, during the "theft mode", the reproduced signals from the deck section and the tuner section are converted into signals by scramble processing, and the audio signals are reproduced as sounds having no musical value.

Therefore, according to the present invention (first to fifth inventions), a person who does not know the personal identification code (user of the stolen audio device) can install the on-vehicle audio device incorporating the antitheft device of the present invention. Even if you try to use, you can't practically use it.

Further, according to the third and fifth aspects of the invention, the sound device is made to notify the user that the disabled state in the "theft mode" is the "theft mode" state on the display unit. It is easy to distinguish it from the failure of the above, and the authorized owner can easily cancel the "theft mode" by inputting the personal identification code and use it as a normal audio device.

Furthermore, it is extremely difficult for a person who does not know the personal identification code to cancel the "theft mode". In other words, even if the on-vehicle audio device incorporating the anti-theft device of the present invention is stolen, the on-vehicle audio device is protected. Since it is extremely difficult to release, the preventive effect of theft prevention can be exerted.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an antitheft device for an on-vehicle audio device according to the present invention.

FIG. 2 is a flowchart showing the operation of the control unit in the theft mode.

FIG. 3 is a block diagram showing the configuration of another embodiment of an anti-theft device for vehicle-mounted audio equipment according to the present invention.

FIG. 4 is an explanatory diagram of scrambling processing.

FIG. 5 is a flowchart showing the operation of the control unit in the theft mode.

FIG. 6 is a conventional example of a theft prevention device for an on-vehicle audio device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 keyboard (input means) 2 memory (storage means) 3 CPU 4 display (limit operation expressing means) 5 battery as a power source (main power source) 7 deck section for reproduction 8 tuner section 9 PLL circuit 10 mute circuit (signal interruption means) 41 A / D converter 42 RAM 43 D / A converter

Front page continuation (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G11B 31/00 519 A 8322-5D H04B 1/06 E 2116-5K

Claims (5)

[Claims] 1. A storage means for storing an identification code, an input means for inputting a personal identification code, and a comparison means for comparing the identification code with the personal identification code, the acoustic device being separated from a main power source, and then again. In an anti-theft device for a vehicle-mounted audio device, which is provided with operation limiting means for limiting the operation of the audio device when the secret code input by the input means and the identification code do not match when connected to a main power source, A first mode detecting means for detecting the first mode in which the operation limiting means is connected to the main power supply again after the audio equipment is separated from the main power supply; and a deck section of the audio equipment during the first mode. Anti-theft device for vehicle-mounted audio equipment, comprising: a blocking means for ejecting the recording medium inserted into the audio equipment and fixing the tuning frequency of the tuner of the audio equipment. Apparatus. 2. The anti-theft device for an on-vehicle audio equipment according to claim 1, wherein the operation limiting means further comprises signal cutoff means for cutting off the demodulated signal from the tuner section during the first mode. A characteristic anti-theft device for in-vehicle audio equipment. 3. The antitheft device for an on-vehicle audio equipment according to claim 1 or 2, wherein the operation of limiting the audio equipment by the operation limiting means during the first mode is the limiting operation of the limiting operation means. An anti-theft device for an in-vehicle audio device, comprising: a restricted operation expressing means indicating that. 4. A storage means for storing an identification code, an input means for inputting a personal identification code, and a comparison means for comparing the identification code and the personal identification code, the acoustic device being separated from the main power source, and then again. In an anti-theft device for a vehicle-mounted audio device, which is provided with operation limiting means for limiting the operation of the audio device when the secret code input by the input means and the identification code do not match when connected to a main power source, A first mode detecting means for detecting the first mode in which the operation limiting means is connected to the main power supply again after the audio equipment is separated from the main power supply; and a reproduction from the audio equipment during the first mode. An anti-theft device for an in-vehicle audio device, comprising: a scramble processing unit that converts and outputs a signal sequence. 5. The anti-theft device for an on-vehicle audio equipment according to claim 4, further indicating that the operation of restricting the audio equipment by the operation restricting means is the restricting operation of the restricting operation means during the first mode. An anti-theft device for an on-vehicle audio device, comprising: a limited operation expressing means.