KEYLESS ENTRY SYSTEM FOR AUTOMOTIVE DEVICES WITH FEATURE FOR GIVING CAUTION FOR LOCKING WIRELESS CODE TRANSMITTER IN VEHICLE

Abstract: A keyless entry system can lock and unlock an automo­ tive vehicle door, a trunk lid, a glove box and/or a steering column without an ignition key. The system comprises a transmitter (100) producing a radio signal indicative of a preset unique code, and a controller (200) receiving the radio signal and performing desired locking or unlocking opera­ tion when the code from the transmitter (100) matches a preset code. A manual switch (210) is provided to order the transmitter (100) to transmit the code-indicative radio signal to the controller (200). The transmitter (100) encloses a battery acting as a power source. Locking the transmitter in the vehicle is detected by detecting that the code signal level remains substantially unchanged for a given period of time after the vehicle is locked. In such cases, an alarm is produced to remind the driver to remove the transmitter (100) from the vehicle cabin by operating the manual switch to open the door. An optional feature disables the keyless entry system if the driver fails the retrieve the transmitter (100) after the alarm.

Description: The present invention relates to a keyless entry system for operating the door lock without requiring a key. US-A-4,205,325 discloses a keyless entry system in which a predetermined code has to be input by a keyboard mounted at the outside of the vehicle. Such keyless entry systems are well developed, however, have the disadvantage that a user can only enter his car when remembering a predetermined code. US-A-4,223,296 describes a system reminding a driver who is leaving his car of his engine key inadvertently left behind in the engine key switch of the car before he shuts car doors in locked condition. If the key is remained, the doors cannot be locked, to remind the driver of the left-behind engine key or an alarm is released. It is an object of the present invention to provide a keyless entry system of high security standard, which does not require to remember a predetermined code. The system of the present invention comprises: an electrical actuator connected to said vehicle device and responsive to a control signal ro reverse said vehicle device between said active and inactive states; a manual switch stationarily mounted at the vehicle and exposed to external access for commanding reversal of the state of said vehicular device; a transmitter responsive to a radio demand signal to output a radio code signal indicative of a unique code which identifies the transmitter, which transmitter has a transmitter antenna installed at a transmitter housing and designed for induction radio signal communication; a controller resopnsive to manual entry of a command through said manual switch for transmitting said radio demand signal through a controller antenna arrangement and recieving said radio code signal from said transmitter through said controller antenna arrangement, comparing the unique code indicated by said radio code signal with a preset code, and procuding said control signal, when said unique code matches said preset code; and a transmitter-locking alarm means comprising a signal level detector responsive to said signal level variations in said code signal within a given period of time to produce an alarm signal when the overall change in said code signal level over said given period of time is less than a predetermined value. In a parallel application having the number 84 111 198 protection is asked for a system comprising the first four of the above listed five features. Such a system has the advantage that it is not necessary to remember a code, as coded signals are transmitted from a transmitter carried by the user. When using such a system, a new problem arises: The transmitter may be left in the car when leaving the car. Then any person may enter the car just by touching the manual switch associated to the door lock. The system as listed above detects whether the transmitter is locked in the vehicle and it produces an alarm when this is the case. The alarm is released when the signal from the transmitter as received by a controller remains within a given range for a given period of time. The given period of time should be selected to be long enough for the user to walk a certain distance away from the vehicle, but short enough to produce the alarm before the user goes too far away to recognize the alarm. Preferably, the just mentioned level detection is only activated when a door lock changes from the unlocked to the locked state. It is to be noted that the use of radio signals in an entry system for a vehicle is already known. GB-A-2 051 442 describes a security system which sounds an alarm when a person tries to unlock a door using a key unless a coded signal is transmitted before, the code of which corresponds to a predetermined code stored by a controller within the vehicle. In another version of the described security system, circuits are kept inoperative to immobilize the car unless signals having the correct code are received. When the user forgets the transmitter within the vehicle, the doors can be unlocked without an alarm being released. However, also in this case, it is necessary to have a key to open the door. Therefore, the danger induced by leaving the transmitter in the car, is not too high - only the extent of security decreases. The present application will be understood more fully from the detailed description given below and from the accompanying drawing of a preferred embodiment. Fig. 1 is a schematic block diagram showing the general concepts of a keyless entry system for an automotive vehicle device according to the present invention; Fig. 2 is a perspective view of an automotive vehicle to which the keyless entry system according to the present invention is applied; Fig. 3 is a block diagram of a transmitter in the preferred embodiment of a keyless entry system according to the present invention; Fig. 4 is a block diagram of a controller in the preferred embodiment of the keyless entry system according to the present invention; Figs. 5(A) and 5(B) are flowcharts of the operation of the transmitter and the controller, respectively; and Figs. 6(A) and 6(B) are flowcharts showing a modified mode of operation of the transmitter and the controller, respectively. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, particularly to Figs. 1 and 2, the preferred embodiment of a keyless entry system for an automotive vehicle according to the present invention generally comprises a code transmitter 100 and a controller 200. The controller 200 is connected via a driver signal generator 204 to actuators 202 for vehicle devices such as door lock device, a trunk lid lock device, a starter motor and a steering lock device. The controller 200 includes a demand signal SD generator 208 which sends a demand signal SD to the transmitter 100 to activate the latter. The demand signal SD generator 208 is connected to one or more manual switches 210 which are placed on the external surface of the vehicle so as to be accessible from outside the vehicle. The demand signal SD generator 208 produces a demand signal SD when one of the manual switches 210 is depressed. As shown in Fig. 3, the transmitter 100 includes a receiver circuit 102 for receiving the demand signal SD from the controller. The transmitter 100 becomes active when the receiving circuit 102 receives the demand signal SD to produce a code signal SC which is indicative of a preset specific code. The preset code of the portable transmitter 100 differs from that of the demand signal SD generator 208 so that the controller 200 can recognize when the transmitter 100 is responding. As shown in Fig. 3, the transmitter 100 encloses a thin, compact, long-life battery 304, such as a mercury battery, acting as a power source. The battery 304 is connected to a transmitter circuit to supply electric power. The transmitter 100 continuously transmits the code signal SC to the controller for as long as it remains active. The code signal SC is received by a receiver 212 in the controller 200. The controller 200 has a comparator 213 to compare the received code with a specific preset code. When the received code matches the code preset as compared in the comparator 215, the controller 200 sends a control signal SL to the driver circuit generator 204. The driver signal generator 204 in turn sends a drive signal to one of the actuators 202 corresponding to the manual switch 210 operated. The actuator 202 in activated by the driver signal from the driver signal generator 204 to operate the corresponding vehicle device. The receiver 212 of the controller 200 is connected to a signal level detector 302 of a transmitter-locking alarm system 300. The signal level detector 302 monitors the amplitude of the code signal SC from the transmitter 100 and produces a signal-level-indicative signal having a value which varies in proportion to the amplitude of the code signal. A signal level variation detector 304 is associated with the signal level detector 302 to detect the degree of change in the signal level within a given period of time. The signal level variation detector compares a detected signal level variation value with a reference value which is indicative of the expected reduction in the amplitude of the code signal within the given period as the user carries the transmitter away from the vehicle. The signal level variation detector 304 produces an alarm signal when the magnitude of the signal level variation is less than the reference value. The alarm signal produced by the signal level variation detector 304 is fed to an alarm device 306 which then produces an alarm or a caution to notify the user that the transmitter 100 is still locked in the vehicle. Since the door lock device can be operated by depressing the manual switch 210 which causes transmission of demand signal from the controller 200 to the transmitter placed inside of the vehicle and of code signal from the transmitter to the controller, the user can easily remove the transmitter 100 from the passenger compartment even if the transmitter 100 should be inadvertently locked in the vehicle. It should be appreciated that, since the vehicle devices to be operated by the first embodiment of the keyless entry system are two-state locking devices for locking and unlocking vehicle doors, the trunk lid and the steering column and two-state starter motor, the actuators 202 actuate the vehicle devices from the current position to the opposite position in response to the driver signal. For instance, when the vehicle device is in the locked position, the actuator unlocks the vehicle device in response to the driver signal. On the other hand, when the driver signal is sent to the actuator of a vehicle device which currently unlocked, that vehicle device is then locked. The transmitter 100 includes a transmitter/receiver antenna 104. In addition, a loop antenna 214 is built into one of the windows 216 of the vehicle. The loop antenna 214 transmits the demand signal SD to and receives the code signal SC from the transmitter 100. As shown in Fig. 2, the manual switches 210 are mounted on an escutcheon 218 of an outside door handle for operation from outside the vehicle. On the other hand, when the vehicle device is the starter motor which is normally off, the actuator turns the starter motor on for the period of time wherein the driver signal is applied thereto. Therefore, the starter motor is operated for the predetermined period of time in which the driver signal remains HIGH. The transmitter 100 is housed in a case small enough to hand-carry or to pocket. Fig. 3 shows the circuit structure of the transmitter 100. A microprocessor 106 is connected to the antenna 104 via a demodulator 108 which demodulates the received demand signal SD, and to the battery 304 via the battery checker 300 to receive power therefrom. The microprocessor 106 includes a memory 110 storing the preset code. In response to the demand signal SD, the microprocessor 106 reads out the preset code to a modulator 112. The modulator 112 is, in turn, connected to a carrier-wave generator 114 to receive a carrier wave. The modulator 112 modulates the carrier-wave with the code-indicative signal from the microprocessor 106 to produce the final code signal SC. In the preferred embodiment, the antenna 104 of the transmitter 100 is built into the transmitter circuit board or on the surface of the transmitter casing 116 (shown in Fig. 2). The casing 116 is the size of a name card and thin enough to carry in a shirt pocket. Fig. 4 shows the circuitry of the controller 200. As set forth above, the shown embodiment of the keyless entry system is adapted to operate the door locks, the trunk lid lock, the starter motor and the steering lock device. In addition, the shown embodiment is adapted to control operation of the locks for the right- and left-side doors independently. In order to allow independent operation of the lock devices, manual switches 210-DR, 210-DL, 210-TL, 210-GL and 210-ST are provided on the vehicle body somewhere nearby the devices to be operated. For example, the manual switches 210-DR and 210-DL are provided adjacent the door handles of respectively corresponding side soors. Similarly, the manual switch 210-TL to operate the trunk lid lock device would be placed adjacent the trunk lid. Though the specific embodiment has been illustrated to locate respective manual switches adjacent the corresponding vehicle devices to be operated, it would be possible to provide all of manual switched in concentric manner on the outside door handle escutcheon 218, for example. Each manual switch is operable independently to operate the corresponding lock device. For example, when the manual switch 210-DR is depressed, the right-side door lock 220-DR is actuated to either to the locked or unlocked state. Each manual switch 210-DR, 210-DL, 210-TL, 210-SM and 210-ST is connected to a timer 222-DR, 222-DL, 222-TL, 222-SM and 222-ST through a normally closed relay 224-DR, 224-DL, 224-TL, 224-SM and 224-ST. The timers, which will be referred to generically with reference numeral "222", are responsive to depression of the corresponding manual switch, which will be referred to generically with reference numeral "210", to produce a HIGH-level timer signal St for a given period of time. This given period of time should be long enough to cover the time required to transmit the demand signal SD from the controller to the transmitter 100 and to receive the code signal SC from the transmitter in return. The timer signal St is fed to a corresponding AND-gate 226-DR, 226-DL, 226-TL, 226-SM and 226-ST, which will be referred to generically with reference numeral "226". At the same time, the timer signal St is fed to a corresponding switching circuit 228-DR, 228-DL, 228-TL, 228-SM and 228-ST, which will be referred to generically with reference numeral "228". The switching circuit 228 closes in response to the timer signal St to connect the corresponding antenna 214-DR, 214-DL, 214-TL, 214-SM or 214-ST, which will be referred to generically with reference numeral "214", to a demodulator 230, whereby the code signal SC received by the corresponding antenna 214 is conducted to the demodulator. The timers 222 are also all connected to a microprocessor 232 via a multi-input OR gate 234. The microprocessor 232 includes a memory 236 which stores the preset code corresponding to that stored in the transmitter 100. The microprocessor 232 responds to the timer signal St received via the OR gate 234 by outputting the demand signal SD to the transmitter through a modulator 238 and antenna 214. The modulator 238 is connected to the antennae 214 via the switching circuits 228 to transmit the demand signal SD to the transmitter 100. The microprocessor 232 receives the code signal SC via the antenna 214 and the demodulator 230 and compares the received code with the stored code. When the received code matches the stored code, the microprocessor 232 outputs the control signal SL to the other input terminal of the AND gate 226 corresponding to the depressed manual switch. Therefore, at this time, AND gate 226 transmits a HIGH-level signal to the driver signal generator 204-DR, 204-DL, 204-TL, 204-SM or 204-ST, which will be referred to generically with reference numeral "204". The driver signal generator 204 responds to the HIGH-level signal by outputting a driver signal to the corresponding actuator 202-DR, 202-DL, 202-TL, 202-SM or 202-ST of the lock 220-DR, 220-DL, 220-TL, 220-SM or 220-ST. The door locks 220-DR and 220-DL are connected to right- and left-side door lock switches 221-DR and 221-DL which turns ON when corresponding door lock is in locking state. The door lock switches 221-DR and 221-DL are connected to the microprocessor 232 to feed HIGH level door locking state indicative signals. The vehicle devices 220 also allows operations in a conventional mechanical key. When the mechanical key is used, the vehicle devices are operated independently of the keyless entry system. The microprocessor 106 of the transmitter 100 repeatedly executes the first control program illustrated in Fig. 5(A). In the first control program, the microprocessor 106 checks for receipt of the demand signal SD from the controller at a step 1002. The step 1002 is repeated until the demand signal SD is received. In other words, the transmitter 100 normally remains in a stand-by state, waiting to produce the code signal SC in response to the demand signal SD. When the demand signal SD is detected at the step 1002, the preset code C₁ is read from the memory 110 at a step 1004. The microprocessor 106 then outputs the code-indicative signal to the modulator 112 which in turn outputs the code signal SC in step 106. Control then returns to the stand-by step 1002. It should be noted that the code signal SC is transmitted from the modulator to the controller for a given period of time and terminates when the given period of time expires. The given period of time during which the code signal SC is transmitted is so chosen that the controller 200 can activate the actuator 202 designated by the operated manual switch before expiration of that period. In addition, the code stored in the memory 110 is preferably a binary code, such as an 8-bit serial datum. This binary code rides on the carrier wave as modulated by the modulator to form the code signal SC. The microprocessor 232 is programmed to sample the amplitude of the received code signal at a first timing upon initial receipt of the code signal and at a second timing a given period of time after the first timing. The microprocessor 232 derives the differences between the amplitudes of the received signals at the first and second timings. The derived amplitude difference is compared with the reference value representing the expected code signal amplitude reduction in cases where the transmitter 100 is not locked in the vehicle. If the difference is less than the reference value, the microprocessor 232 outputs an alarm signal to the alarm device 306 to activate the latter. The operation of the microprocessors in the transmitter 100 and the controller 200 will be described in more detail with reference to flowcharts of control programs executed thereby. The flowchart of Fig. 5(A) summarizes the first control program executed by the microprocessor 106 in the transmitter 100 and the flowchart of Fig. 5(B) summarizes the second control program executed by the microprocessor 232 of the controller 200. Fig. 5(B) is a flowchart of a program executed concurrently and independently of the that illustrated in Fig. 5(A). In initial step 2002, the output of OR-gate 234 is checked if any of the manual switches 210 have been depressed. If not, the program ends and is repeated again from the beginning. If one or more of the manual switches 210 has been closed, control passes to step 2004 wherein the demand signal S D is broadcast for reception by the transmitter 100. Thereafter, the microprocessor 232 waits at step 2006 for receipt of the code signal S C from transmitter 100. Upon receipt of code signal S C , its amplitude S₁ is recorded in step 2008 for later use and then a read-time counter or timer is reset and started in step 2010. In this embodiment, the timer clocks a predetermined period of time which is long enough for the signal level from a slowly receding transmitter to diminish noticeable, but not so long as to allow a walking driver to leave sight or earshot of the vehicle and its alarm device 306. Following step 2010, the demodulator 230 and microprocessor 232 extract the coded information from the code signal S D in step 2012. The analogous code information is then retrieved from memory 236 in step 2014 for verification of the received code. if the received code matches the stored code when checked in subsequent step 2016, then the vehicle device associated with the particular manual switch closed in step 2002 is actuated in step 2018. An incorrect code match at step 2016 causes the current cycle of program execution to end. Of the steps executed up to this point, only step 2010 is directly concerned with checking for a transmitter left in the passenger compartment by a foretful driver. In fact, if the program were to end here, bypassing the subsequent steps 2022-2032, the keyless entry system could still function satisfactorily, although without the alarm feature described later. This would actually be preferrable in cases where only the glove box, trunk, starter, or the like are being used, as in such cases there is no chance of the driver leaving without the transmitter and an alarm to that effect would only be a niusance. Accordingly, in step 2020 following actuation step 2018, the door switch positions are checked to check if all of the doors are checked. If it was the all of the doors being locked, the program continues to step 2022 et seq., as this is the only instance in which an alarm might be useful. Although which device is to be actuated and its state of actuation at any time are not easy to check in the circuit shown in Fig. 4, modern vehicles commonly have accessory safety systems which monitor door locks and the like, and such a system may be tapped to detect when the driver's door or other doors are being locked. Of course, step 2020 may be omitted altogether. In step 2022, the microprocessor 232 waits for the timer activated in step 2010 to count out the predetermined period of time. After this period has elapsed, the demand signal S D is again transmitted in step 2024 to elicit the code signal S C from transmitter 100. The amplitude S₂ of the received code signal is again sampled in step 2026, and this value is subtracted from or divided into the signal amplitude value S₂ recorded earlier to obtain an amplitude change value ΔS in step 2028. The amplitude change value ΔS is then compared in step 2030 to a reference amplitude change value ΔS ref which represents a minimal expectable drop in the signal level of the code signal S C if the transmitter 100 were being carried away from the vehicle. If the detected change ΔS matches or exceeds the predetermined threshold value ΔS ref , then it can be assumed that the driver has taken the transmitter with him or her, and the program ends without further operation. Otherwise an alarm is produced in step 2032 to warn the driver of his impending mistake. It should be noted that the predetermined period of time spent predominantly at step 2022 needs to be selected suitably, but that this can be done with confidence. Specifically, since the transmitter 100 will be quite close to the antennas 214 when the manual switch 210 is first depressed and the transmitted signal level will drop off with the square of the distance from the vehicle thereafter, a significant amplitude drop should be resolvable after only a short time. In the shown embodiment as set forth above, since the code signal SC is output only when the demand signal SD is input from the controller, consumption of electric power of the battery in the transmitter is significantly reduced in comparison with system which might employ constant transmission of the code signal SC. Thus, the life-time of the battery of the transmitter is prolonged even though electric power is constantly supplied to the microprocessor to hold same in stand-by. It should be appreciated that the electric power needed to power the microprocessor is substantially smaller than that consumed in transmitting the code signal SC. Therefore, constant power supply to the microprocessor will not significantly affect the life-time of the battery. Similarly, since the demand signal SD is produced only when at least one of the manual switches is depressed, consumption of the electric power by the controller is significantly limitted. It is also to be noted that transmission of the demand signal SD and the code signal SC is performed by electromagnetic induction. Since locking and unlocking operations of the lock devices will generally be performed only when the transmitter is near the controller, good communication between the transmitter and the controller can be obtained by electromagnetic induction without significant power consumption. In order to unlock the right-side door lock device 220-DR, the manual switch 210-DR is depressed. When the ignition switch 302 is in the OFF position, the timer 222-DR becomes active to output the timer signal St. The timer signal St is applied to the AND gate 226DR and to the switching circuit 228-DR, the latter of which then closes to connect the antenna 214-DR to the microprocessor 232. The timer signal St from the timer 222-DR is also input to the microprocessor 232 via the OR gate 234. The microprocessor 232 responds inputs from the OR gate 234 by activating the modulator 238 to transmit the demand signal SD via the antenna 214-DR. The demand signal SD transmitted via the antenna 214-DR is received by the antenna 104 of the transmitter 100. Then, the demand signal SD is demodulated by the demodulator 108 to remove the carrier-wave components. The microprocessor 106 of the transmitter 100 then executes the steps 1004 and 1006 of the first control program of Fig. 5(A) and outputs the code-indicative signal to the modulator 112. The modulator 112 thus transmits the code signal SC to the controller 200 via the antenna 104. The code signal SC is received by the antenna 214-DR and fed to the demodulator 230. The demodulator 230 demodulates the code signal SC to remove the carrier-wave components. The microprocessor 232 receives the demodulated code signal SC and executes the steps 2008 to 2016 of the second control program. When the input code matches the preset code in the memory 236, the microprocessor 232 feeds the control signal SL to the AND gate 226-DR. At this time, since the timer signal St is still being applied to one of the input terminals of the AND gate, the AND condition of the timer signal St and the control signal SL is established and as a result, the AND gate passes a HIGH-level signal to the driver signal generator 204-DR which produces the driver signal. The driver signal is applied to the actuator 202-DR of the right-side door lock device 220-DR to reverse the lock position. Since the right-side door lock device 220-DR was originally locked, it becomes unlocked upon activation of the actuator 202-DR. Similarly, when the manual switch 210-DL is closed to operate the left-side door lock device, the antenna 214-DL sends the code signal SC to the microprocessor. If the input code matches the preset code, the AND gate 226-DL opens to activate the driver signal generator 204-DL. Thus, if the left-side door lock device is originally unlocked, it becomes locked. When the manual switch 210-TL is operated, the timer 222-TL become active to send a timer signal St to the AND gate 226-TL and the switching circuit 228-TL. The switching circuit 228-TL then closes to establish electrical communication between the antenna 214-TL and the demodulator 230 and the modulator 238. The code signal SC is transmitted from the transmitter 100 to the antenna 214-TL in response to the demand signal SD. If the input code is the same as the preset code, then the AND gate 226-TL opens to activate the driver signal generator 204-TL. Therefore, the trunk lid lock device 220-TL switches from its current position to the other position. When the manual switch 210-GL is operated to open the glove box lid, the timer 222-GL is activated to output the timer signal St. In response to the timer signal St, the switching circuit 228-GL establishes electrical communication between the antenna 214-GL and the demodulator 230. The code signal SC transmitted from the transmitter 100 is thus demodulated by the demodulator and input to the microprocessor 232. The AND gate 226-GL opens in response to the control signal SL from the microprocessor 232 to activate the driver signal generator 204-GL by the gate signal thereof. In response to the driver signal from the driver signal generator 204-GL, the actuator 202-GL become active to reverse the position of the glove box lid lock from locked state to the unlocked state to allow access to the glove box. In order to release the steering wheel from the locked state, the manual switch 210-ST is depressed. The timer 222-ST becomes active to output the timer signal St for the given period of time. During the period of time in which the timer 222-ST is active, the antenna 214-ST is connected to the microprocessor 232 via the demodulator 230 to receive the code signal SC from the transmitter 100. When the input code matches the preset code in the memory 236, the driver signal generator 204-ST outputs the driver signal to reverse the position of the steering lock device 220-ST from the locked state to the unlocked state. Fig. 6 is a flowchart of a modified version of the program illustrated in Fig. 5(B), from which it differs only by the inclusion of steps 2017 and 2034-2040. These added steps enhance the alarm feature of Fig. 5(B) by locking up the keyless entry system in cases where an alarm is produced in step 2032 but not heeded, so that the transmitter 100 remains locked inside the vehicle. This lock-up feature prevents unauthorized entry via the manual switches 210, forcing the vehicle user to re-enter the vehicle by means of conventional mechanical keys after forgetting the transmitter. Step 2017 is inserted between steps 2016 and 2018 and serves to prevent actuation of any vehicle devices by means of the keyless entry system in cases of lock-up. Specifically, a lock-up flag F L is checked at step 2017 and if set, the program ends rather than proceeding to step 2018. The flag F L is normally reset, allowing normal program flow from step 2016 to step 2018, and can only be set in step 2040 described below. Step 2034 follows step 2032. After the alarm is produced, the timer is restarted in step 2034 to clock a second predetermined period of time allowed for the driver to re-enter the vehicle and retrieve the transmitter. In subsequent step 2036, the timer value is checked to see if the second period has expired. During the second period, control passes from step 2036 to step 2038, in which the output of OR-gate 234 is again checked to see if any manual switches are being operated. If so, the current program cycle ends; otherwise, control returns to step 2036. After the second period has expired without actuation of any of the manual switches 210, control passes from step 2036 to step 2040, in which lock-up flag F L is set. Thereafter, the program ends and step 2017 takes effect, locking up the keyless entry system. When the keyless entry system is disabled as set forth above, the vehicle devices, i.e. door locks, trunk lid lock, and so forth, are operated by means of a mechanical key.

Claims: A keyless operating system for an automotive vehicle locking device for setting the vehicle locking device to either locked or an unlocked state, said system comprising an electrical actuator (202) connected to said vehicle locking device and responsive to a control signal to reverse said vehicle locking device between said locked and unlocked states; a manual switch (210) stationarily mounted at the vehicle and exposed to external access for commanding reversal of the state of said vehicle locking device; a transmitter (100) responsive to a radio demand signal to output a radio code signal indicative of a unique code which identifies the transmitter, which transmitter has a transmitter antenna (104) installed at a transmitter housing and designed for induction radio signal communication; a controller (200) responsive to manual entry of a command through said manual switch for transmitting said radio demand signal through a controller antenna arrangement (214;) and receiving said radio code signal from said transmitter through said controller antenna arrangement, comparing the unique code indicated by said radio code signal with a preset code, and producing said control signal, when said unique code matches said preset code; and a transmitter-locking alarm means (302 ... 306) comprising a signal level detector (302) responsive to said signal level variations in said code signal within a given period of time to produce an alarm signal when the overall change in said code signal level over said given period of time is less than a predetermined value. A system as set forth in claim 1, characterized in that said transmitter-locking alarm means produces said alarm signal when said code signal level is substantially unchanged within said given period of time. The system as set forth in claim 1 or claim 2, characterized in that said transmitter locking alarm means includes a detector (304) for detecting actuation of a door lock device to the locked state from the unlocked state in response to said code signal, and for enabling said signal level detector when the door lock device is actuated to the locked state from the unlocked state.

Inventors: HIRANO, MOTOKI, TANIGUCHI, YOSHIYUKI
Applicants: NISSAN MOTOR CO., LTD.
Application year: 1984
Main classification: E05B49
IPC codes: G07C9, E05B65, E05B49