Ulllted States Patent
`Luebke et al.
`
`[19]
`
`[11] Patent Number:
`45 Date of Patent:
`
`6,034,617
`9
`Mar. 7 2000
`
`US006034617A
`
`8/1991 Tholl et al.
`:C<C>11f16(lla1-
`e or
`..
`307/10.2 X
`12/1996 Kersten .......
`34g6872/$63;
`£233;
`g‘?y1‘v’S et ‘*1’
`'
`'
`3
`1°“ ''''' "
`307/10.2
`/1998 Glehr
`.. . .. 340/426
`8/1998 Iitsuka . . . . . . . . .
`340/825.31
`8/1998 Hettich etal.
`9/1999 Lhamon ........................... .. 340/825.44
`OTHER PUBLICATIONS
`
`
`
`........................ .. 123/179.2
`2
`
`5,042,439
`§,2§‘9Ligg
`,
`,
`5,583,486
`§’g(1)§’:_3§
`5,723,911
`,
`,
`5 790 015
`5:790:043
`5,959,545
`
`Mehrdad Foroozesh, “Protecting Your Data With Cryptog-
`raphy,” UNIX Review, Nov. 1996, V14, n12, p. 55(6).
`_
`_
`Primary Exam;/1er—Thornas Mullen
`Attorney, Agent, or Firm—Quarles & Brady LIP
`
`[75]
`
`[54] OPERATOR INTENT BASED PASSIVE
`KEYLESS VEHICLE CONTROL SYSTEM
`Inventors: Charles J_ Luebke, Sussex, Wis‘;
`Thomas J. Waraksa, Clarkston; John
`D. Prainito, Rochester Hills, both of
`.
`_
`Mlch-é Rlchard C- Barthel»
`_
`Libertyville, 111.; David 11-_ Kahl,
`Waterford; J=1meSA- Pmrler, Sterlmg
`Heights, both of Mich.
`
`[73] Assign“: Eaton Corporatiom C1eVe1and> Ohio
`
`[21]
`
`z\ppl.PJo; 09/205,914
`
`[22]
`
`Filed:
`
`Dec. 4, 1998
`
`[57]
`ABSTRACT
`Int. Cl.7 ...................................................... .. G06F 7/04
`[51]
`U.S. Cl.
`................................... .. 340 825.31‘ 307 '10.2'
`52
`Apassive remote operating system is disclosed which may
`/
`[
`]
`’
`34/0/522’
`:’:rf1.:”C{’%)°3':‘l1§;§a‘“e§:$;;fi
`fcfnfnfiffngifitioii
`[58] Field of Search ......................... 340/825.31, 825.34,
`y
`’P
`340/825.69, 522, 539, 573.1, 426; 307/102;
`‘ 3
`V .
`‘
`1
`76 :;*;::::;:;:;::11::: 5111:2111::::;;1e,::.‘£:,1?;1:;;
`reception trtelinge of a cogtrol cireu1%in thetvelgicrtlte, which the(ri1
`receives
`e comrnan
`signa .
`eceip o
`e comman
`signal activates the control circuit to begin sensing for an
`aC;1‘.°E l.’yd.thetd"V°r’. Stud} as ‘t’p°””t‘°"tfif 3 ‘L90; hégdle’
`W 1°.
`1“ ‘Ca ‘’s. an 1“ .°“ 1°‘?
`0 °“ 5”
`° "C 19°‘
`P0“
`sensing that action within a given period after receipt of the
`command signal, the doors of the Vehicle are unlocked.
`
`[56]
`
`Re. 30,686
`2,679,601
`4,674,454
`4,688,036
`4,928,778
`5,000,139
`
`References Cited
`U.S. PATENT DOCUMENTS
`7/1981 Bucher .................................. 290/38 R
`5/1954 Hart
`..................................... .. 307/10.6
`61,1987 Phairr _________________________________ __ 123/1792
`8/1987 Hiram ct a1.
`.
`N 340/825.07
`
`. . . . . .. 180/167
`5/1990 Tin . . .. . . . . . . . .
`3/1991 Wong ................................. .. 123/179.2
`
`20 Claims, 3 Drawing Sheets
`
`CONTROL
`LOGIC
`
`46
`
`ASSA 100
`
`1
`
`ASSA 1008
`
`

`
`U.S. Patent
`
`M
`
`0
`
`3M1a
`
`6,034,617
`
`0‘M37:o_oo._Hmozéozmw._oEz8
`
`good
`
`om
`
`$5.8m5%.33
`
`.9H29:5
`
`
`
`
`
`%~m_$_$m_.:n_._.Dom_o._.om_.En_#zozoz
`
`8
`
`2
`
`
`
`

`
`U.S. Patent
`
`Mar. 7,2000
`
`Sheet 2 0f3
`
`6,034,617
`
`SEND ID &
`
`
`
`ACTIVE
`
`COMMAND
`
`64
`
` MOTION
`DETECTOR
`
`
`
`
`PASSIVE COMMAND
`
`
`ACTIVE
`
`YES
`
`7 -
`
`SEND ID AND
`
`FIG. 2
`
`3
`
`

`
`U.S. Patent
`
`Mar. 7,2000
`
`Sheet 3 0f3
`
`6,034,617
`
`SIGNAL RECEIVED
`
`N0
`
`70
`
`72
`
`
`
`PASSIVE
`COMMAND
`2
`
`NO
`
`YES
`
`76
`
`SET DELAY TIMER
`
`74
`
`GO TO ACTIVE
`COMMAND
`ROUTINE
`
`78
`
`80
`7
`
`
`
`
` DRIVER
`INTENTION TO
`
`UNLOCK
`
`UNLOCK
`
`YES
`
`DOORS
`
`NO
`
`TIMER
`
`NO
`
`ELAl;SED
`
`3
`
`YES
`
`END
`
`4
`
`

`
`6,034,617
`
`1
`OPERATOR INTENT BASED PASSIVE
`KEYLESS VEHICLE CONTROL SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`invention relates to keyless systems for
`The present
`gaining entry into motor Vehicles, and more particularly to
`passive remote keyless vehicle entry systems, which do not
`require activation by a user.
`Automobiles traditionally have used mechanical keys and
`locks to protect against unauthorized access to the vehicle.
`However, mechanical
`locks are vulnerable to a criminal
`forcibly removing the lock cylinder, thereby being able to
`release the door catch without a key. Other vulnerability
`arises from the ability to duplicate easily most mechaincal
`keys.
`With the increased use of electronic systems in vehicles
`came the ability to provide more sophisticated access con-
`trol. Remote keyless entry (RKE) systems commonly take
`the form of a fob which is attached to the driver’s key ring.
`The fob houses a radio transmitter which sends a digital code
`via a radio frequency (RF) signal to the vehicle when the
`driver presses a switch on the fob. The digital code prevents
`spurious radio signals from activating the door lock, as well
`as making it difficult for unauthorized persons to gain access
`to the motor vehicle. The RF signal also encodes whether the
`user wishes the doors to be locked or unlocked, the trunk to
`be unlatched or another function to be performed, as deter-
`mined by which switch on the fob is pressed by the user.
`Encryption algorithms often are employed to make it
`extremely difficult for a thief to eavesdrop on the fob
`transmissions and learn the security codes.
`A receiver mounted in the motor vehicle detects the
`
`transmission from the fob and decodes the RF signal to
`determine whether it is Valid for that vehicle and which one
`
`of the various functions is to be performed. The receiver then
`activates the appropriate components to perform that func-
`tion.
`
`Conventional keyless entry systems require that the user
`activate the fob by pressing a switch in order to send a signal
`to the vehicle. If the user’s arms are carrying packages or a
`child, it may not be convenient to activate the small fob
`located in a pocket or purse. Thus it is desirable to provide
`a passive keyless entry system that does not require fob
`activation by the user.
`It is not uncommon for a family to have two or more
`vehicles each with a separate fob for remote access. This
`requires a person to either select the correct fob for the
`vehicle that is desired to be driven or to carry a fob for each
`vehicle. Thus it is advantageous to permit a single fob to
`access multiple vehicles. However, it is undesirable to have
`a single transmission from this fob unlock several vehicles
`when the user only wants access to one.
`SUMMARY OF THE INVENTION
`
`A general object of the present invention is to provide a
`passive remote keyless vehicle entry system which does not
`require manual activation by the user.
`Another object is to provide an unlocking sequence that
`protects vehicles from being unlocked inadvertently.
`These and other objectives are satisfied by a keyless
`motor vehicle control system having a remote control
`adapted to be carried by a driver. The remote control
`occasionally transmits a command signal. In the preferred
`embodiment, the remote control senses when it is moving
`and while moving periodically transmits the command sig-
`nal.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`A receiver in the vehicle receives the command signal
`from the remote control, and in response produces a receiver
`signal. A sensor also is located on the vehicle to detect an
`action by the driver which indicates an intention to operate
`the device. That action may involve touching a part of the
`vehicle such as a door handle or lock cylinder, or the driver
`simply being within a given distance from the vehicle. A
`sensor signal is produced to indicate the occurrence of that
`action by the driver.
`A controller in the motor vehicle is connected to the
`
`sensor, the receiver and a device to be operated, such as the
`door locks. An activation signal is sent to the device when
`the controller receives the receiver signal and the sensor
`signal. Preferably,
`the activation signal is produced only
`when the sensor signal is received within a predefined period
`of time after receipt of the receiver signal.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block schematic diagram of a remote keyless
`entry (RKE) system for a motor vehicle; and
`FIG. 2 is a flowchart of the process by which a portable
`remote control of the RKE sends commands to a control
`circuit in the vehicle; and
`FIG. 3 is a flowchart of the sequence by which the control
`circuit processes the command
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`With initial reference to FIG. 1, a keyless motor vehicle
`control system 10 comprises a portable remote control 12
`carried by a driver and a control circuit 14 located in the
`motor vehicle. The control circuit 14 includes a controller 16
`
`such as a microcomputer with an internal memory in which
`a control program and operating data are stored. A conven-
`tional clock circuit 22 supplies timing pulses to the control-
`ler 16. Aplurality of manual input switches 24 and 25 enable
`a service technician to place the controller 16 into different
`operating modes, such as a programming mode in which
`access codes are stored in the controller’s memory.
`The control circuit 14 also incorporates a mechanism
`which detects the proximity of a person to the motor vehicle.
`This mechanism may constitute a conventional proximity
`detector 26, such as one that transmits ultrasound, micro-
`waves or infrared light and senses when that radiation is
`reflected back by an object in close proximity to the vehicle.
`Alternatively, the proximity sensor can be replaced by a
`switch 27 that closes when someone touches or operates a
`door handle of the vehicle. Such a switch may be a capaci-
`tive sensor at the door handle.
`
`The control circuit 14 operates several functions, such as
`locking and unlocking the doors and unlatching the trunk lid.
`For that functionality, the controller 16 is interfaced to the
`corresponding actuating devices on the motor vehicle. In
`some motor vehicles, the various functions are controlled by
`an another computer to which the controller 16 sends
`operating commands via a communication bus 18. In other
`installations, the controller 16 has individual output lines 20
`connected directly to the control devices for the respective
`functions to be operated. Specifically, separate wires may be
`coupled to actuators which lock and unlock the doors and
`unlatch the trunk lid.
`
`A serial output line 28 and a serial input line 29 of the
`controller 16 are connected to a first radio frequency trans-
`ceiver 30. The first transceiver 30 modulates a standard radio
`frequency carrier with the serial data received on line 28 and
`
`5
`
`

`
`6,034,617
`
`3
`transmits that modulated radio frequency signal via an
`antenna 32. The first transceiver 30 also demodulates other
`
`radio frequency signals received by the antenna 32 to
`recover serial digital data which then is sent via line 29 to the
`controller 16.
`
`The first transceiver 30 is designed to communicate with
`a second radio frequency transceiver 40 within the remote
`control 12, which may have the form of a key ring fob. The
`second transceiver 40 has a receiver section coupled to an
`antenna 42. The receiver section demodulates a received
`
`radio frequency signal to recover digital data that modulates
`that signal and the recovered data is sent in a serial format
`to an input register 44. The input register 44 converts the
`serial data stream from the second transceiver 40 into a
`parallel format which is read by a control logic 46. The
`control
`logic 46 may be either a hardwired device for
`sequentially performing the remote control operations, or a
`programmable device which executes a software program to
`perform those operations. Control logic of this general type
`is similar to that used in previous types of RKE transponders
`and their conventional technology can be utilized to imple-
`ment the functions of the present control logic 46.
`The control logic 46 of the remote control 12 is connected
`to an electrically erasable programmable read only memory
`(EEPROM) 48 which stores codes to be transmitted to the
`motor vehicle control circuit 14 when the remote control is
`
`activated. A clock circuit 52 provides timing signals for the
`remote control 12. A plurality of user operable switches 54
`are connected to different input lines of the control logic 46
`allowing the driver to select the specific functions to be
`performed on the motor vehicle. For example, a pair of
`switches can be provided for locking and unlocking the
`passenger doors, while another switch is for unlatching the
`trunk lid. In addition a motion detector 55, for example a ball
`in a cage type, provides an input signal to the control logic
`46 whenever the remote control 12 is being moved, such as
`when the driver carrying the remote control is walking.
`The remote control 12 also includes an encryptor 50
`connected to the control logic 46 to encrypt a remote control
`security number for transmission to the control circuit 14.
`The encryptor 50 utilizes a secret-key cryptography algo-
`rithm to encrypt data being transmitted. For example, the
`algorithm specifies a sequence of logical operations which
`are performed on a known seed number and a challenge
`number received from the control circuit 14 to produce a
`security number for transmission by the remote control.
`Several cryptography algorithms of this type are described
`by Mehrdad Foroozesh in an article entitled “Protecting
`Your Data With Cryptography,” UNIX Review, November
`1996, V14, n12, page 55(6), which description is incorpo-
`rated herein by reference. These types of encryption tech-
`niques and algorithms are commonly used to encrypt com-
`puter data being transmitted over common carriers.
`Digital data to be transmitted is sent by the control logic
`46 in parallel form to a parallcl-in/scrial-out output register
`56. The serial data from the output register 56 is applied to
`the input of a transmitter section in the second transceiver 40
`which modulates a radio frequency carrier signal with that
`data. The resultant RF signal is sent via the antenna 42 to the
`control circuit 14 in motor vehicle. The components of the
`remote control preferably are powered by a battery (not
`shown).
`The remote control 12 can be employed in a conventional
`manner to unlock the doors of the vehicle or unlatch the
`trunk lid. In this instance,
`the driver presses one of the
`switches 54 that corresponds to the desired function. This
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`action causes the control logic to transmit a signal to the
`control circuit 14 in motor vehicle. That signal carries a
`unique identification code for that particular remote control
`12 and a designation of the selected function. If the control
`circuit 14 recognizes that remote control identification code
`as being authorized to operate this particular vehicle, the
`control circuit 14 immediately activates the desired function
`on the vehicle. This is an active mode of operation, as it
`requires action by the driver in order for the keyless motor
`vehicle control system 10 to operate.
`The keyless motor vehicle control system 10 also operates
`in a passive mode in which the driver or other user does not
`have to press a switch on the remote control 12. With
`reference to FIG. 2, the remote control 12 typically is in a
`“sleep state” in which most of its circuits are not powered to
`conserve battery power. When the user presses one of the
`switches, the control logic “wakes up” as denoted by step 60.
`Upon identifying a switch closure the process branches to
`step 62 at which a command signal is transmitted to the
`control circuit of the vehicle as described immediately
`above.
`
`If a switch closure is not detected, the process advances
`to step 64 where the input from the motion detector 55 in the
`remote control 12 is examined. If motion is not occurring,
`the remote control enters the sleep state at step 66.
`Otherwise,
`the process branches to step 68 at which the
`remote control transmits its identification code and a com-
`mand indicating the passive mode. Specifically the control
`logic 46 in FIG. 1 obtains the identification code and the
`passive mode command from the EEPROM 48 and uses that
`data to form the message packet to send. The message packet
`is transferred in parallel to the output register 56 and then
`sent serially to the second radio frequency transceiver 40
`from which the signal is transmitted via antenna 42. The
`second radio frequency transceiver 40 transmits the passive
`command signal at a lower power level at step 68 than the
`power level used to send the active command at step 62. This
`lower power level conserves the battery in the remote
`control 12.
`
`Thereafter at step 69, the remote control sets a timer to a
`given dclay period. When the delay pcriod expires the
`process executed by the remote control 12 returns to step 60.
`It should be understood that if at anytime during the delay
`period the user activates one of the switches on the remote
`control 12, the process immediately jumps to step 60.
`Thus while the remote control 12 is in motion, as occurs
`when it is being carried by a moving user, the remote control
`identification code and the passive command are periodi-
`cally being sent from the second radio frequency transceiver
`40.
`
`When the person with the remote control 12 is within
`approximately two meters of the vehicle, for example, the
`control circuit 14 will receive the passive mode signal from
`the remote control. Upon detecting a signal on the proper
`carrier frequency, the control circuit 14 begins executing a
`signal processing routine depicted by the flowchart of FIG.
`3. At step 70, the identification code from the received signal
`is inspected to determine if it
`is one that has been pro-
`grammed into the controller as designating a remote control
`that is authorized for this particular vehicle. If not, process-
`ing of the received signal terminates. It should be understood
`that the authentication procedure may be more involved
`when an encryption algorithm is employed for greater
`security, as mentioned previously.
`If the identification code is from an authorized remote
`control, the signal processing advances to step 72 at which
`
`6
`
`

`
`6,034,617
`
`5
`a determination is made by the microcomputer of controller
`16 whether the signal carried a passive command. If not the
`process branches to step 74 and a routine that responds to
`active commands. When the passive command is found at
`step 72 the signal processing branches to step 76.
`At this juncture, a delay timer within controller 16 is set
`to a predefined period at step 76. Next, the controller makes
`a determination at step 78 whether the driver has an intention
`to enter the vehicle. Rather than simply unlocking the
`vehicle when the control circuit receives the passive com-
`mand signal, an additional act is required on the driver’s part
`before unlocking occurs. Otherwise, the mere presence of
`the driver near the vehicle, such as simply walking along an
`adjacent sidewalk, would unlock the doors even when the
`person carrying the remote control has no intention of
`entering the vehicle. Several different mechanisms can be
`employed to provide an indication of a driver’s intent to
`enter a vehicle.
`
`The first of these mechanisms involves touching a door of
`the vehicle. For example, a switch 27, shown in FIG. 1, may
`be connected to the door handle to provide a signal when the
`driver operates that handle. This switch 27 could be a
`capacitive type sensor connected to the door handle to detect
`touching by the driver. However, it may be preferred to
`connect the capacitive type sensor to the lock cylinder of the
`door, because a driver often operates the door handle upon
`exiting the vehicle to ensure that the door is locked. As the
`remote control 12 already may have sent the passive com-
`mand to the control circuit 14, the driver’s test operation of
`the door handle will unlock and open the door when the
`detection mechanism is attached to the handle. Alternatively,
`the passive remote unlocking may be inhibited for a period
`of time upon the vehicle being locked.
`Aproximity sensor 26 may be used to detect the intention
`of a driver to enter the vehicle after the passive command
`has been received. This conventional proximity detector 26
`may be one that transmits ultrasound, microwaves or infra-
`red radiation and senses when that radiation is reflected back
`
`by an object in close proximity to the vehicle. In order to
`prevent an inanimate object, such as a lamp post, a tree or
`another vehicle, from being erroneously detected and caus-
`ing the doors to unlock, the range of the proximity detector
`should be relatively small, e.g. less than one meter.Amotion
`detector, similar to those used in security systems, also can
`be employed to detect the proximity of the driver and yet
`exclude false triggering by inanimate objects.
`Alternatively, detection of the driver‘s intention to enter
`the vehicle can be based on the strength of the passive
`command signal received by the control circuit 14. The
`vehicle will unlock only when that signal strength exceeds
`a predefined level which corresponds to the driver being in
`close proximity (e.g. within one meter) of the vehicle. In this
`embodiment,
`the first
`radio frequency transceiver 30
`includes a circuit for measuring the signal strength and
`providing an indication to the controller 16 when the pre-
`defined level is exceeded.
`
`When one of these proximity detection mechanisms is
`used, it is necessary to inhibit the passive unlocking of the
`vehicle immediately upon locking until the driver has moved
`beyond the range of the proximity detector or the receiver of
`the first radio frequency transceiver 30. Otherwise,
`the
`vehicle will unlock immediately as the driver, upon exiting,
`is within the range of the proximity detector and the first
`radio frequency transceiver 30.
`Referring again to FIG. 3, when the driver’s intention to
`unlock the vehicle is found at step 78 the controller 16
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`responds by sending a signal that unlocks the doors. Oth-
`erwise the process advances to step 82 at which the status of
`the timer is examined. If the delay period has not elapsed the
`process returns to step 78 to test again for the driver’s
`intention to enter the vehicle. The signal processing termi-
`nates when the timer expires at step 82. Thus if a valid
`passive command is received and the driver does not act in
`a manner that indicates an intention to enter the vehicle
`
`within the delay period, the control circuit 14 cancels the
`passive command and returns to wait for another signal from
`the remote control 12.
`
`The foregoing description is directed primarily to pre-
`ferred embodiments of the invention. Although some atten-
`tion was given to various alternatives within the scope of the
`invention, it is anticipated that skilled artisans will likely
`realize additional alternatives that are now apparent from the
`disclosure of those embodiments. Accordingly, the scope of
`the invention should be determined from the following
`claims and not limited by the above disclosure.
`We claim:
`
`1. A method for operating a device on a motor vehicle
`using a system which includes a remote control carried by a
`driver and a control circuit in the motor vehicle, said method
`comprising the steps of:
`
`the remote control occasionally, automatically transmit-
`ting a command signal;
`the control circuit, upon receiving the command signal,
`sensing an action by the driver which indicates an
`intention to operate the device, and
`sending an activation signal to the device in response to
`sensing the action by the driver.
`2. The method as recited in claim 1 further comprising the
`remote control detecting when the remote control is moving.
`3. The method as recited in claim 2 wherein when the
`
`remote control is moving, the remote periodically transmits
`the command signal.
`4. The method as recited in claim 1 wherein sensing an
`action by the driver comprises sensing the driver touching
`the motor vehicle.
`
`5. The method as recited in claim 1 wherein sensing an
`action by the driver comprises sensing the driver touching
`part of a door lock of the motor vehicle.
`6. The method as recited in claim 1 wherein sensing an
`action by the driver comprises sensing the driver operating
`a door handle of the motor vehicle.
`
`7. The method as recited in claim 1 wherein sensing an
`action by the driver comprises sensing the driver being
`within a given distance of the motor vehicle.
`8. The method as recited in claim 7 wherein sensing the
`driver being within a given distance of the motor vehicle
`comprises transmitting radiation from the motor vehicle and
`detecting reflection of that radiation back to the motor
`vehicle.
`
`9. The method as recited in claim 1 wherein sensing an
`action by the driver comprises detecting an object moving
`within a given distance of the motor vehicle.
`10. The method as recited in claim 1 wherein the sensing
`an action by the driver must occur within a predefined period
`of time from when the control circuit received the command
`
`signal in order for the activation signal to be sent to the
`device.
`
`7
`
`

`
`6,034,617
`
`7
`11. An apparatus for operating a device on a motor
`vehicle, the apparatus comprising:
`a remote control adapted to be carried by a driver, the
`remote control occasionally, automatically transmitting
`a command signal;
`a receiver on the vehicle to receive the command signal
`from the remote control and in response produce a
`receiver signal;
`a sensor on the vehicle to detect an action by the driver
`which indicates an intention to operate the device and
`in response produce a sensor signal; and
`controller in the motor vehicle and connected to the
`sensor, the receiver and the device, the controller upon
`receiving the receiver signal and the sensor signal sends
`an activation signal to the device.
`12. The apparatus as recited in claim 11 wherein the
`remote control includes a motion detector and wherein the
`
`command signal is sent in response to the motion detector
`sensing movement of the remote control.
`13. The apparatus as recited in claim 11 wherein the
`sensor detects the driver touching part of the motor vehicle.
`14. The apparatus as recited in claim 13 wherein the
`sensor is a capacitive sensor connected to the part of the
`motor vehicle.
`
`8
`15. The apparatus as recited in claim 11 wherein the
`sensor comprises a switch coupled to a door handle of the
`motor vehicle.
`
`16. The apparatus as recited in claim 11 wherein the
`sensor detects when the driver is within a given distance of
`the motor vehicle.
`
`17. The apparatus as recited in claim 16 wherein the
`sensor detects strength of a signal from the remote control to
`determine when the driver is within a given distance of the
`motor vehicle.
`
`18. The apparatus as recited in claim 16 wherein the
`sensor transmits radiation and detects reflection of that
`radiation.
`
`19. The apparatus as recited in claim 18 wherein the
`sensor transmits radiation selected from the group consisting
`of infrared light, microwaves and ultrasound.
`20. The apparatus as recited in claim 11 wherein the
`controller produces the activation signal only when the
`sensor signal is received within a predefined period of time
`after receipt of the receiver signal.
`
`5
`
`10
`
`15
`
`20
`
`8