WO1989000520A1

WO1989000520A1 - Car radio with theft protection

Info

Publication number: WO1989000520A1
Application number: PCT/DE1988/000390
Authority: WO
Inventors: Günter LIHL
Original assignee: Digatec Electronic Systems Gmbh
Priority date: 1987-07-20
Filing date: 1988-06-29
Publication date: 1989-01-26
Also published as: DE3723931A1; EP0376951A1

Abstract

A car radio with theft protection comprises a microprocessor (40) connected to a store (54) for recording sharp and flat tuning codes, a separate device for inputting a code (emitter 58) connected to a separate receiving device (receiver 56), at least one tuner (22, 24), a low-frequency part, and a display unit (48). The receiver (56) is connected to a comparator (53) which in turn is connected to the store (54). The output of the comparator (53) is connected via an interrupt line (52) to the microprocessor (40), which is activated or inactivated depending on the signal transmitted by the interrupt line (52). The microprocessor is connected via a bus line (38) to a synthetizer (28), the tuner (22, 24), the low-frequency part (34), and the display unit (48), and controls all these elements.

Description

Description: Car radio with anti-theft device

The invention relates to a car radio with anti-theft device, which a) a microprocessor to which a memory for coding for arming and disarming is assigned, b) a separate device for entering a code with an associated receiving device and c) at least one tuner, one LF amplifier and a display unit.

In this car radio with anti-theft device known from DE-OS 36 37 019, the sound output signal is switched off when it is determined by means of the microprocessor that the external voltage supply has been interrupted. The known car radio has a code setting device for setting an anti-theft code and a code entry device controlled by the microprocessor. The code supplied by the code setting device is only passed on to the microprocessor if an appropriate identification number has been entered via the code input arrangement.

A disadvantage of this previously known car radio, however, is that by connecting an auxiliary voltage source, for example a small battery, which has the same voltage as the external motor vehicle battery, during an unauthorized removal, i.e. theft, of the car radio, the car radio is simulated that the voltage source is still is present, i.e. is not interrupted. If an auxiliary voltage source is connected before the known car radio is removed, the main voltage source can be interrupted without triggering an alarm or other consequences.

Even if a thief consciously accepts a possible alarm by deliberately knowing the battery cable when removing the known car radio cuts through, the device is not unusable as a result, it is sufficient to bridge the switch in the device that interrupts the LF path in order to be able to operate the previously known car radio. The car radio can also be operated after the NF switch has been bridged if the identification code is not known. The latter can, however, be read out of the device, in particular for specialists, provided the device is stolen and can be opened and inspected in peace.

The previously known car radio does not provide adequate security against theft.

Given the large number of thefts of expensive car radios, it must be assumed that there are a large number of specialized thieves for whom car radio security systems are somewhat of a challenge, which are trying to overcome this security system and thus to secure the car radio in question stand. Since the expansion of a car radio can now be carried out in a very short time for a specialist, so that a thief - even if an alarm system is activated - has long been looking for space before someone responds to the alarm Duration of the actual expansion appeals, ultimately not sufficient.

This is where the invention comes in. It has set itself the task of creating a car radio that can practically no longer be used after theft.

This object is achieved on the basis of the car radio of the type mentioned at the outset in that the receiving device is connected to a comparator which in turn is connected to the read-only memory, that the output of the comparator is connected to the microprocessor via an interrupt line and a status line, in that the Microprocessor is either inactive or active depending on the signal of the interrupt line, and that the microprocessor has a bus line with a synthesizer, the tuner, the AF amplifier and the display unit. is connected this controls.

Adequate security against theft only exists if the stolen car radio cannot be used later because it is inoperative due to the security circuit and cannot be put back into operation by simple interventions - as with the previously known car radio. Protection against theft is given if the stolen car radio is practically worthless for the thief because it cannot be put into operation even by a specialist. Theft for the purpose of reselling the stolen car radio is practically impossible in these circumstances.

Essential features of the invention are thus the combination of a microprocessor-controlled car radio and the connection of this microprocessor to the code device, which consists of the separate input device and the receiving device and which switches the microprocessor active or inactive. In the "arming" operating state, ie inactive microprocessor, the entire car radio is inactive. It cannot be switched on or operated. Even in the event of theft and after dismantling, the function of the device can no longer be established. In the "disarmed" operating state, the car radio can be operated as normal, it is enabled.

The safety device thus acts on the individual components of the actual car radio via the microprocessor. Since the microprocessor controls all essential functions of the actual car radio via the bus line, the car radio is inactive without the function of the microprocessor and is therefore practically worthless, the microprocessor is, so to speak, the "heart" of the car radio, without which a function is not possible ¬ is. This has the consequence that the car radio cannot be put into operation by intervening in the individual stages, for example tuner, LF amplifier or display unit. The disadvantage of the car radio of the type mentioned, in which the car radio function can be restored by simple measures, namely by bridging the switch iti NF branch, is not present in the car radio according to the invention, this can only be put back into operation be when its microprocessor is started. The interaction between the microprocessor and the code device can, however, be secured sufficiently electrically and mechanically that successful interventions in this area are practically impossible. In other words, the electrical and mechanical protection can be designed so securely that it will not be possible even for a specialist who examines a stolen device in peace and with all technical aids to change the microprocessor from the "inactive" state to the "active" state "to bring back.

The mechanical and electrical safety devices mentioned can be of different types, some options are shown below:

1. If the comparator, the read-only memory and the microprocessor are housed in a single semiconductor component, access to the interrupt line is practically impossible, at least only possible if the component itself is opened and the internal interrupt connection is found. In any case, external access is only possible via the code signal, which is usually not available to a thief and is stored in the separate device for input.

2. If the comparator, read-only memory and microprocessor are accommodated in a mechanically encapsulated part of the car radio, for example in a metal fuse box, access to the three levels mentioned is extremely difficult, and in general there is generally no access to the interior possible. The mechanical fuse can at the same time be connected to an electronic measure, for example, after opening the security box, a switch is actuated, which deletes the memory content of the microprocessor. Even after access to the interior of the fuse box, the car radio can only be brought into a functional state if the internal processing program of the microprocessor is reloaded.

3. Furthermore, at least some of the data that the micro- Processor for its work program, in particular a part of its internal operating program, needs to be accommodated in the separate input device, the arrangement being such that the corresponding information is read into the microprocessor each time the car radio is set to "sharp""is switched to the" disarmed "state. It is part of the operating program of the microprocessor that, when changing to the arming position, it deletes that part of its internal operating program which it received via the separate input device. This means that the microprocessor cannot be operated without entering the appropriate data and the car radio is therefore useless if this additional information is not available.

4. Finally, it has proven to be very advantageous to supplement a memory, for example the RAM memory, with a random generator which has a memory for the last random number. The connection between the transmitter and the Sipfänger is bidirectional, the receiver has a transmitter part, the transmitter has a reception part. With each setting and / or with each unsetting, the random code is transmitted to the transmitter via the transmitting part of the receiver and stored there. The next setting process (shaft unset) can only take place if this random code is broadcast again by the transmitter and is received by the receiver. The storage of the last random number in the transmitter is only deleted when a new random number is sent to the transmitter via the car radio.

Only in the event that the transmitter is lost, a second input code is stored in the car radio, which is created individually for each car radio and is only known to the manufacturer of the car radio, this code is deposited in a safe. If the rightful owner of the car radio turns to the manufacturer with a corresponding proof, he receives a second key, which first sends out the additional code, but then works like the normal first key. These four measures mentioned can be combined and modified as desired.

The two-way connection between transmitter and receiver is fundamentally advantageous for the receiver to acknowledge the information provided by the transmitter.

A characteristic feature of the invention is that the microprocessor is inactive in the armed state of the safety device and cannot be brought back into the active state without special knowledge of information which is accommodated in the separate input device. This means a different concept for anti-theft devices than is previously known for car radios: until now it was common for the car radio to receive information about whether it was stolen or not via the security device. The state of "stolen" is generally detected by the safety device according to the prior art in that the car radio is connected in some form to the motor vehicle in which it is installed and when this connection is released (for example connection to the motor vehicle -Battery, contact with the slide-in bracket, etc.) an alarm is triggered.

In the car radio according to the invention, the triggering of an alarm is not primarily intended or intended, but it should not be ruled out either. However, the decisive factor for the invention is not the triggering of an alarm, but rather the deactivation of the car radio in the "armed" state. In this state, the car radio - regardless of whether it is stolen or not - is worthless for a user and can only be used if the separate input device is present and is being used. In the case of the car radio according to the invention, the moment of theft is therefore not detected by the security device, but is in principle switched to security if this is specified via the separate input device.

An additional alarm is advantageous, however, it can be used, for example, to save the memory content for the program memory of the To completely erase the microprocessor, so that a thief is additionally prevented from putting the car radio into a functional state.

It has proven to be very advantageous to provide a memory in the car radio for digital storage of an individual voice input and, if appropriate, for digital storage of telephone numbers. Individual data of the rightful owner or purchaser of the car radio is stored in this memory by means of a special charging device and associated software, exclusively from the manufacturer and only from a selected group of people there. In the event of theft, the stored information is retained. In the event of theft, it can be used to output an acoustic warning message or to dial predetermined numbers in the background via an existing car telephone system. After the telephone connection has been established, the information contained in the memory is transmitted.

The separate input device, in which the data necessary for activating the car radio is stored, can be designed in any way: it can interact mechanically, for example via contacts, with the actual car radio. In general, however, it is remote-acting, for example it contains an acoustic, optical or electromagnetic transmitter, and the receiving device is accordingly designed in the actual car radio.

Further advantages and features of the invention emerge from the remaining claims and the following description of an exemplary embodiment which is not to be understood as restrictive and which is explained in more detail with reference to the drawing. The drawing shows:

Fig. 1 is a schematic diagram in the form of a block diagram of a car radio with safety device and

2 shows a schematic diagram for the arrangement of the comparator, microprocessor and associated parts in an encapsulated area, including illustration of further security measures. The car radio shown in Fig. 1 has a synthesizer tuning system. In this case, high-frequency signals are received in a known manner by means of an antenna 20 and fed to a tuner. An EM tuner 22 and an AM tuner 24 are shown. These are connected via a line 26 to a synthesizer 28, the latter supplying the respective active tuners 22, 24 a tuning voltage which is used to provide a frequency in the tuner generate which is mixed with a received RF signal so that a predetermined intermediate frequency is obtained. This is amplified and demodulated in a stage 30 designated "IF / Demodulator" and passed on to a LF part via a line 32. The switchover between the provided tuners 22, 24 takes place by means of a range selection stage 36.

Synthesizer 28, LF part 34 and range selection stage 36 are connected to one another via a bus line 38, to which a microprocessor 40 and a display unit 42 are also connected. The microprocessor 40 controls the actual car radio via this bus line 38.

The microprocessor 40 is connected to a keyboard 44, this is done via a line 46. If an input frequency is set or specified via this keyboard 44 directly or via its transmitter search device, this is passed on to the microprocessor 40 using the synthesizer 28, which automatically prejudges the corresponding leveling. The microprocessor 40 not only controls the tuners 22, 24 and the synthesizer 28 via the internal bus line 38, but also on the one hand the volume in the LF part 34 and on the other hand the display unit 42, on the output side with the actual display 48, both for example, an LCD display is connected.

If the microprocessor 40 in such a car radio is out of operation, ie inactive, no function of the car radio is possible. The keyboard 44 directly connected to the microprocessor 40 has no effect, since it is only connected to the microprocessor 40 and only via this to the other stages. Tuning the tuners 22 or 24 is also impossible because the microprocessor 40 is also required for this. Control of the LF output is on - without a control signal the bus line 38 - not feasible. There is also no display since the display unit 42 does not receive any information via the bus line 38.

This configuration and exclusive alignment of the actual car radio with the microprocessor 40 is the basis for the anti-theft system according to the invention.

The anti-theft device is discussed below: An interrupt input of the microprocessor 38 is connected via a line 52 to the output of a comparator 53. A memory 54, designated RAM in FIG. 1, is assigned to this and on the input side it is connected to a receiver 56 which interacts with a transmitter 58. The transmitter 58 forms the separate device for entering a code, the receiver 56 is the associated receiving device. In the exemplary embodiment shown, the transmitter and receiver 56, 58 optically communicate, other designs are possible.

If the transmitter 58 is actuated, it sends out a packet of information. This is received by the receiver 56 and passed on to the comparator 53. This compares the information received by the receiver 56 with the information stored in the RAM 54. If the two items of information match, then an output takes place on the interrapt line 52. The microprocessor 40 is then alternatively blocked or released.

In the exemplary embodiment shown in FIG. 1, a status line 60 is additionally provided, which connects the microprocessor 40 on the input side to the output of the comparator 53. It shows the state in which the microprocessor 40 is located. It is also linked to a time loop 62 which, in a known manner, blocks access to the microprocessor 40 for a predetermined period of time which increases as a function of the number of failed attempts.

A memory 64 is connected to the microprocessor 40, in which the program and the data for the work processes are located in the microprocessor 40. This memory needs a voltage source for the memory function, therefore it is assigned an internal battery 66, which is preferably designed in the form of a small accumulator or as a lithium battery. This battery 66 ensures that the content of the memory 64 is retained even when an external current supply is present Supply, in particular the power supply via the motor vehicle battery, is interrupted. The RAM 54, on the other hand, is a non-volatile memory that does not require a power supply to store its data. The same applies to the data memory in the transmitter 58, this is preferably a so-called fuseable ROM.

The microprocessor 40, the comparator 53 and the two memories 54, 64 are located within a mechanically protected area 68, indicated by dashed lines in FIG. 1, which can be seen in more detail in FIG. 2. There is shown a metal capsule 70 which is closed on all sides and has a number of insulated bushings 72 on two sides. In the interior of the metal capsule 70 are the parts surrounded by the dashed line 68 in FIG. 1 and additionally an alarm transmitter or load resistor 74. This is used as follows: Some of the connections to the bushings 72 are via resistors which are located on the Printed circuit board 76 are connected together. If this loop is severed by severing one of the relevant connections 78, in particular by unsoldering the printed circuit board 76, and if the microprocessor is also inactive, either the alarm signal sounds via the alarm transmitter 74, which at the same time loads the battery 66 and is exhausted after a certain time. As a result, the content of the memory 64 is erased. In the event of a load resistance instead of the alarm transmitter 74, no alarm is triggered, but the same effect is achieved, that is to say the information present in the memory 64 is deleted.

The lithium battery 66 is also accommodated within the capsule 70, it is connected with its one pole, preferably the negative pole, to the metallic wall of the capsule 70 and is only connected via this to the corresponding line on the printed circuit board, so that the battery connection is interrupted as soon as an attempt is made to open the capsule 70. If the power supply to the memory is interrupted, the Content of memory 64 no longer maintained, that is to say erased. With its other pole, the battery 70 is connected to the printed circuit board in an easily accessible manner. This connection can be opened in a targeted manner if one wishes to delete the contents of the memory.

The printed circuit board 76 is connected to a four-wire line 80, via which the power supply, that is to say the connection to a motor vehicle battery, takes place. Two wires of this line 80 are used for the actual power supply, the other two wires are used for an alarm loop, it being possible that one wire can also be used as a stand-by line. The alarm loop is terminated in an associated socket 82 with a resistor. If this socket 82 is disconnected from the associated plug 84 or if the line 80 is cut through, the alarm loop is open; an alarm is output in a known manner, in particular via a built-in loudspeaker or the alarm transmitter 74.

Finally, a microswitch 86 is provided which is opened when the radio is pulled out of its holder.

In a further development in which the transmitter 58 not only transmits the packet of information to the receiver 56 which is stored in the RAM 54, but also subsequently sends out further information which is part of the program which is in the memory 64 is stored, the comparator switches through after checking the first part, that is to say the RAM information, and allows the further information to reach the microprocessor 40 via the status line 60 so that it can be stored in the memory 64 . They remain stored there until a new command from transmitter 58 is issued again. With this new command, the stored information is first deleted and then the microprocessor 40 is switched to inactive.

A further improvement is achieved in that the microprocessor 40, the comparator 62 and the two memories 54, 64 are accommodated on a semiconductor substrate and thus in a housing. In this case, the lines 52, 60 are only after opening the housing of the Semiconductor device accessible. This can also be accommodated in a capsule 70, as described above.

Data can only be read into the memory 64 via an interface, which only enables data transfer to the memory 64, but not from it. For this purpose, for example, a photodiode 77 is provided, which is embedded in the wall of the capsule 70 and is firmly connected to it. This diode 77 is supplied with the data via a T.FΠ (diode), which is not provided in the car radio. Reading the data from the memory 64 is extremely difficult as a result.

The coding of the information contained in the RAM memory 54 and thus also in the transmitter 58 takes place at the manufacturer of the car radio and is known only to a very small group of employees. The relevant information is kept inaccessible to the general public. A random generator is used in the selection of the identification information in order to avoid that the coding is recognized on the basis of a continuous law.

The transmitter 58 is made as small as possible, it is the size of a key fob. If it is lost, another electronic key with the correct coding can be produced by presenting a proof of purchase and the serial number. The information output by the transmitter 58 is either encrypted or modified by double modulation in such a way that the content cannot be decrypted by querying the emitted signal.

Claims

Expectations

1. Car radio with anti-theft device that includes a microprocessor (40) which is associated with ^"provide a memory (54) for coding for focusing and disarmed, and a separate device for entering a code (transmitter 58) and an associated receiving means (Brpfänger 56), at least one tuner (22, 24), an LF part and a display unit (48), characterized in that the receiver (56) is connected to a comparator (53) which in turn is connected to the memory (54) is sen angeschlos¬ that the output of the comparator (53) via a line Interrupt¬ (52) is connected to the microprocessor (40) that the microprocessor ^"(40) circuit in response to the signal of the Interrupt¬ (52) either is inactive or active, and that the microprocessor (40) is connected via a bus line (38) to a synthesizer (28), the tuner (22, 24), the LF part (34) and the display unit (48) and controls it.

2. Car radio according to claim 1, characterized in that the comparator (53) is additionally connected via a status line (60) and preferably additionally via a time loop (62) to the microprocessor (40).

3. Car radio according to claim 1 or 2, characterized in that the microprocessor (40), the comparator (53) and the memory (54, 64) are in a mechanically protected part, in particular in a capsule (70).

4. Car radio according to one of claims 1 to 3, characterized in that the microprocessor (40), the comparator (53) and the two memories (54, 64) are arranged on a semiconductor substrate and are housed in a common component housing.

5. Car radio according to one of claims 1 to 4, characterized in that the information transmitted by the transmitter (58) on the one hand and in time beforehand comprises the information contained in the memory (54) and on the other hand and in time thereafter contains information which is part of the data contained in the memory (64), and that an erasure device is provided for this data of the memory (64).

6. Car radio according to one of claims 1 to 5, characterized in that a turning part is also housed in the receiver (56) to which an Eirpfangteil the transmitter (58) is assigned so that the connection between the Bipfänger (56) and transmitter (58 ) is bidirectional.

7. Car radio according to claim 6, characterized in that the transmitting part in the receiver (56) is connected to the memory (64) or the memory (54) and by this after each vo receiver (56) recorded arming or disarming the Car radios receive a random code, which is transmitted from the transmitting part of the receiver (56) to the transmitter (58) and stored in the transmitter (58) in a memory provided there, and that this random code is a necessary component of a transmission signal of the transmitter (58 ) for later arming or disarming.

8. Car radio according to one of claims 1 to 7, characterized in that it has a memory in which in digitalized form individually inputable speech data are stored via a charging device provided for this purpose, which, for example, provide information about the rightful owner of the car radio and / or at least include a telephone number, which is automatically dialed in the event of the theft beginning to be detected by the car radio, via an existing car telephone system, after which the voice announcement is made.