United States Patent [19]
`Rackley
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,742,357
`May 3, 1988
`
`[54] STOLEN OBJECI‘ LOCATION SYSTEM
`[76] Inventor: Ernie C. Rackley, 1704 Rock?eld,
`Troy, Mich. 48098
`[21] Appl. No.: 908,156
`.
`.
`sep' 17’ 1986
`[22] Elm‘
`[51] Int. Cl.‘ .............................................. .. G015 3/02
`[52] US. Cl. .................................. .. 342/457; 342/450;
`342/463; 342/383
`
`[56]
`
`of Search ....................... ..
`342/457, 450, 463-465, 387, 389, 45, 455, 456
`References Cited
`U‘s' PATENT DOCUMENTS
`Re. 31,962 7/1985 Brodeur ............................ .. 342/389
`3,646,530 2/ 1972 Fuller ct 81-
`' 342/457 X
`3,665,312 5/1972 Jar‘"§_ ------ "
`32/61)‘
`3’747’1o4 7/1973 Panslm ‘ ‘ ' ‘ ' ‘ '
`' ' ' ' "
`2/ 57
`3,886,554 5/1975 Braun et al.
`342/457
`4,023,176 5/1977 Lume et aL n
`342/457 X
`4,145,692 3/1979 Armstrong at a’
`____ __ 342/173
`4,177,466 12/1979 Reagan ............ ..
`340/63 X
`4,229,620 10/1980 Schaible
`342/457 X
`4,494,119 V1935 wimbush
`---- ~ 342/ 457
`
`Assistant Examiner—-Tod R. Swann
`‘$13212; £53?’ or Flrm_James R‘ Ignatowskl; Remy
`'
`P
`ABSTRACT
`[57]
`A stolen object location system having a base station, a
`location network and an object unit which is associated
`with the object to be located. The location system is
`capable of operating in a plurality of different location
`modes ranging from simple triangulation to LORAN.
`The base Station’ upon being noti?ed that the Object has
`been stolen, will transmit a locate request message to
`the1 032cc: unit specifying the locaticfin?rlnode) ‘to in used
`e 0 _]CC unit’s
`e ransmisslon requency o
`an
`transmitter. An electronic control in the object unit will
`control the operation of the object unit’s receiver and
`transmitter in accordance with the location mode and
`transmission frequency speci?ed in the locate request
`message. The electronic control will also initiate the
`.
`.
`.
`.
`.
`transmissioniof an alarm message if the object unit loses
`communicatlon with the base station, and is capable of
`transmitting a tattle-tale message, effectively relaying
`the alarm message of another object unit if the base
`station does not respond to the other object unit’s alarm
`
`4,638,294 l/ 1987 Sakurai . . . . . .
`. . . . . . .. 340/63
`4,651,157 3/1987 Gray et a]. .................... .. 342/450 X
`Primary Examiner—-Thomas H. Tarcza
`
`message_
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`36 Claims, 10 Drawing Sheets
`
`30“
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`GOOGLE 1015
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`US. Patent
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`May 3, 1988
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`10
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`4,742,357
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`US. Patent
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`May 3, 1988
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`Sheet 3 0f 10
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`U.S. Patent
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`May 3,1988
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`

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`US. Patent May 3,1988
`
`Sheet 5 0f 10
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`4,742,357
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`US. Patent
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`May 3, 1988
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`Sheet 6 of 10
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`4,742,357
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`US. Patent May 3,1988
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`Sheet 7 0f 10
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`4,742,357
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`US. Patent
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`May 3, 1988
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`Sheet 8 of 10
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`4,742,357
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`US. Patent May 3, 1988
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`Sheet 9 0f 10
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`4,742,357
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`US. Patent
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`May3, 1988
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`Sheet 10 of 10
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`4,742,357
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`1
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`STOLEN OBJECI‘ ‘LOCATION SYSTEM
`
`4,742,357
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`2
`a ground station from the time a location request signal
`is received at each of the three satellites. The well
`known passive LORAN (Long Range Navigation) sys
`tem is still another method that may be used to deter
`mine a vehicle’s location.
`Although the various location techniques are well
`known, the utilization of these techniques for the loca
`tion of a stolen vehicle or object have not been fully
`exploited by the prior art, nor does the prior art teach a
`location system in which the transmission times by the
`vehicle mounted unit are not very short, difficult to
`detect, and dif?cult to jam or confuse.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The invention is related to the ?eld of radio location
`systems and, in particular, to a system for locating sto
`len objects or objects removed from the owner’s posses
`sion.
`2. Description of the Prior Art
`One of the major problems facing the owner of an
`object or item having any value is the fact that there is
`a relatively high probability of it being stolen. In partic
`SUMMARY OF THE PRESENT INVENTION
`ular, automobiles, trucks, the contents of trucks, air
`craft, boats, and various types of off-road vehicles are
`The invention is a system for the location of an ob
`the primary targets of thieves. These vehicles may be
`ject. The system includes an object unit associated with
`moved a considerable distance in a very short time,
`the object to be located, a location network, and a base
`making recovery dif?cult, if not impossible. This prob
`station. The object unit has at least one receiver for
`lem has been further aggravated in recent years by the 2
`0 receiving locate request messages and echo pulses trans
`advent of the so called “chop shops” in which a stolen
`mitted by the base station, a variable frequency trans
`vehicle may be disassembled for parts in less than one
`mitter for transmitting messages and relaying the re
`hour, extinguishing any hope of recovery.
`ceived echo pulses, and an electronic control for con
`As is known, it is almost impossible to prevent the
`trolling the operation of the receiver and the variable
`vehicle from being stolen. Experienced thieves can
`frequency transmitter in response to the information
`break into a locked vehicle and drive it away in less than
`contained in the locate request message. The informa
`a minute while others have used a tow truck to steal the
`tion contained in the locate request message includes at
`vehicle. It, therefore, would be advantageous to locate
`least an identi?cation number uniquely identifying the
`the vehicle as soon as possible after it has been stolen to
`object unit associated with the object to be located, a
`prevent it from being disassembled in a “chop shop”,
`temporarily hidden for subsequent resale, or trans
`mode code identifying one of at least two different
`location methods to be used to locate the object, and a
`ported out of the state. In many of these cases, and in
`frequency code identifying the transmission frequency
`particular in the case of the “chop shop”, the owner or
`the police may have less than an hour to locate the
`of the variable frequency transmitter. The electronic
`vehicle if there is to be any hope of recovery.
`controller has means responsive to the identi?cation
`This problem is addressed by the auto theft detection
`number contained in the locate request message being
`system taught by Reagan in U.S. Pat. No. 4,177,466. In
`the same as its own identi?cation number to activate the
`Reagan’s theft detection system, each vehicle is identi
`object unit, means for placing the receiver and transmit
`?ed by a unique code and each vehicle has a transpon
`ter in the location mode identi?ed by the mode code
`der responsive to its unique code to transmit a continu
`and to change the transmission frequency of the vari
`ous locating signal. A plurality of location stations hav—
`able frequency transmitter to the frequency identi?ed
`ing proximity detection receivers and/or direction ?nd
`by the frequency code. The location network cooper
`ing receivers, will generate signals indicative of the
`ates with the messages and signals transmitted by the
`proximity of the vehicle to a particular location station
`base station and the object unit to generate signals and
`or the direction of the vehicle from each of a plurality
`messages to be used to determine the object’s location.
`of receivers so that its location can be determined.
`The base station includes a transmitter for transmitting
`Another location system is taught by Jarvis in U.S.
`the location request messages and the echo pulses, a
`Pat. No. 3,665,312. In Jarvis’ system, a radio alarm is
`receiver for receiving the messages and relayed echo
`activated by an illegal entry detector. Upon the detec
`pulses transmitted by the object unit and an operation’s
`tion of an illegal entry, the detector will activate a mul
`controller responsive to external inputs for ‘activating
`tiple frequency transmitter to transmit a coded signal
`the transmitter to generate the locate request messages
`which uniquely identi?es that particular vehicle. The
`and responsive to the messages and echo pulses re
`transmitter will sequentially shift the transmission fre
`ceived from the object unit and the messages generated
`quency at predetermined and different time intervals.
`by the location network to determine the location of the
`The transmitted signals are received by a plurality of
`object.
`direction ?nder receivers which permit the location of
`55
`One advantage of the location system is that it is
`the vehicle to be determined.
`capable of using several different location modes and
`In addition to proximity detectors and direction
`can be used even if one or the other mode is inoperative
`?nder receivers, various other methods are available for
`so that at least one location method is always available.
`radio location of a transmitting source. Wimbush, in
`Another advantage of the location system is that the
`U.S. Pat. No. 4,494,119, discloses a distress radio loca
`tion system in which remotely located slave repeaters
`transmissions by the object unit are short and at differ
`report the strength of a received distress signal to a
`ent frequencies and, therefore, are difficult to detect and
`jam. Another advantage of the location system is that
`central station. The central station computes the vehi
`cle’s location from the strength of the distress signal at
`the power level of the object unit may be changed to
`each of the various slave repeaters. GEOSTAR is an
`enhance the accuracy of the location system when using
`other type of location system using three remotely posi
`direction ?nding receivers.
`tioned satellites. As described in Popular Science, Febru
`These and other advantages of the stolen object loca
`ary 1984, pp 76-78 and 130, the location is computed by
`tion system will become more apparent from a reading
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`?cation number, to the direction ?nding receivers. The
`of the detailed description in conjunction with the
`drawings appended hereto.
`direction ?nding receivers will lock on to the message
`transmitted by the vehicle unit 10 and each generate a
`BRIEF DESCRIPTION OF THE DRAWINGS
`message which is communicated to the base station 30.
`These messages will contain data indicative of the direc
`FIG. 1 is a block diagram showing the basic elements
`tion from which the transmission was received. The
`of the location system of the present invention;
`data transmitted by the receivers will correspond to the
`FIG. 2 is a block diagram of the location system in
`angle measured from a reference direction, such as true
`the direction or distance-triangulation location modes;
`north, as shown in FIG. 2. For example, the directional
`FIG. 3 is a block diagram of the location system in
`receiver RECI will transmit the angle 01, REC2 will
`the distance-direction location mode;
`transmit O2, and REC3 will transmit 03. The base sta
`FIG. 4 is a block diagram of the location system in
`tion 30, knowing the location of the three direction
`the LORAN location mode;
`?nding receivers RECl, REC2, and REC3, and the
`FIG. 5 is a block diagram of the vehicle unit 10;
`angles at which each receives the signal transmitted
`FIG. 6 is a block diagram of the base station 30;
`from the vehicle unit 10, can compute the exact location
`FIG. 7 is a circuit diagram of the vehicle unit’s re
`of the vehicle using a well-known triangulation algo
`ceiver and transmitter;
`rithm. This location can then be converted to the grid
`FIG. 8 is a block diagram of the ECU 14;
`coordinates of a map identifying the location of the
`FIG. 9 is an overall flow diagram of the system;
`vehicle. As is possible, the vehicle may be suf?ciently
`FIG. 10 is a ?ow diagram of the idle routine;
`FIG. 11 is a flow diagram of the read input routine;
`close to one or more of the direction ?nding receivers
`such that the transmitted signal will saturate their direc
`FIG. 12 is a flow diagram of the read bytes routine;
`tion ?nding receivers and degrade its angle detection
`FIG. 13 is a ?ow diagram of the de?ne message rou
`accuracy. In this case, the direction ?nder receiver will
`tine;
`transmit a code to the base station signifying that its
`FIG. 14 is a ?ow diagram of the keep alive routine;
`receiver was saturated. In response to this code, the
`and
`base station 30 will transmit another message to the
`FIG. 15 is a flow diagram of the location request
`vehicle unit 10 requesting that it repeat its transmission
`routine.
`at a reduced power level. This procedure will be re
`peated until none of the direction ?nding receivers
`report a saturated condition, insuring maximum accu
`racy of the measured angle.
`The second mode is a distance-triangulation (DST)
`mode in which the distance of the stolen vehicle is
`measured from three remotely located receivers, such
`as receivers RECl, REC2, and REC3, in FIG. 2. In this
`location mode, the base station 30, upon being noti?ed
`that the vehicle is stolen, will transmit a message to the
`vehicle unit 10. This message will contain at least the
`vehicle identi?cation number, a ?ag or code identifying
`the location method as the distance-triangulation mode,
`and the frequency at which the vehicle unit 10 is to
`transmit. This same information is transmitted to the
`three receivers so they can adjust their reception fre
`quency to the same frequency. In response to this mes
`sage, the vehicle unit 10 will activate an echo channel
`and await the transmission of an echo pulse by the base
`station 30. After a short period of time, the base station
`30 will transmit an echo pulse which is received by the
`vehicle unit 10 and the three remotely located receivers.
`The vehicle unit 10 will echo pulse to the three receiv
`ers after a predetermined delay. Each of the receivers
`will start a timer in response to the echo pulse transmit
`ted by the base station 30 which will be stopped in
`response to receiving the echo pulse retransmitted by
`the vehicle unit 10. Each receiver will report to the base
`station 30 the time between the reception of the echo
`pulse transmitted by the base station 30 and the echo
`pulse transmitted by the vehicle unit 10. The base sta
`tion will then be able to determine from these time
`measurements the distance of the vehicle unit from each
`of the three receivers.
`The third location method that is capable of being
`used by the vehicle unit 10 is a distance-direction mea
`suring (DDM) mode, illustrated in FIG. 3. In this loca
`tion mode, the location network includes a single direc~
`tion ?nding receiver REC4 located adjacent to the base
`station 30, to prevent ambiguity. The direction ?nding
`receiver REC4 may be one of the three direction ?nd
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`The location system-will be described with reference
`to a stolen vehicle; however, the location system is not
`limited to stolen vehicles, but may be used to locate any
`object which may be stolen or removed from the own
`er’s posession. FIG. 1 is a block diagram of a stolen
`vehicle location system. The system includes a vehicle
`unit 10 which is mounted in the vehicle which is to be
`located, a stationary base station 30 having a transceiver
`capable of communicating with the vehicle unit 10, and
`a location network 50 capable of receiving transmis
`sions from or transmitting to the vehicle unit 10 for
`location purposes. The vehicle may be an automobile,
`truck, aircraft, boat, or off-road vehicle. The location
`network 50 may consist of one or more receivers or
`transmitters, which are in direct communication with
`the vehicle unit 10 and/or the base station 30 as shall be
`explained hereinafter.
`The vehicle or object unit 10 is capable of operating
`in at least two, but preferably three or four, different
`types of location modes upon command from the base
`station 30. The ?rst location mode is a direction-triangu
`lation (DRT) mode in which a transmission by the vehi
`cle unit 10 is received by a location network, which
`consists of at least three remotely located direction
`?nding receivers designated RECl, REC2, and REC3,
`as shown in FIG. 2. In this vehicle location mode, the
`base station 30, upon being noti?ed that the vehicle is
`stolen, will transmit a message to the vehicle unit 10.
`This message will contain, at least, a vehicle identi?ca
`tion number uniquely identifying the stolen vehicle, a
`?ag or code identifying the location method as the
`direction-triangulation mode, and the frequency at
`which the vehicle unit 10 is to transmit. The same infor
`mation is also transmitted to the direction ?nding re
`ceivers so that they can adjust their reception frequency
`to the vehicles unit’s transmission. In response to this
`message a transmitter in the vehicle unit 10 will transmit
`a short message, normally containing the vehicle identi
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`ing receivers REC], RECZ, or REC3, used in the trian
`gulation method illustrated in FIG. 2, or a separate
`direction ?nding receiver. As before, the base station
`30, upon being noti?ed that the vehicle has been stolen,
`will transmit a message to the vehicle unit 10 which,
`again, will contain its vehicle identi?cation number, a
`flag or code identifying the location mode as the dis
`tance-direction measuring mode, and a code specifying
`the frequency at which the vehicle unit 10 is to transmit.
`In response to this message, the vehicle unit 10 will
`activate its echo channel and await a second transmis
`sion by the base station 30. After a short period of time
`the base station 30 will transmit an echo pulse and simul
`taneously start a timer. As in the distance-triangulation
`method, the vehicle unit 10 will receive the echo pulse,
`then retransmit it back to the base station 30 after a
`precise ?xed period of time. The timer in the base sta
`tion 30 will measure elapsed time between the transmis
`sion of the echo pulse and the receipt of its transmission
`from the vehicle unit 10. The base station 30 will then
`subtract the precise delay period from the elapsed time
`and compute the distance “d” of the vehicle from the
`base station 30. The algorithm for computing distance
`“d” is the same as used for radar ranging, which is well
`known in the art. Simultaneously, the direction ?nder
`receiver REC4 will measure the angle 04, which is the
`direction of the vehicle from the base station 30. Know
`ing both the direction and distance of the stolen vehicle
`from the base station 30, its position can be converted to
`map coordinates for pin-pointing its location.
`The fourth method for locating the vehicle is based
`on the well known LORAN (Long Range Navigation)
`system developed by the Coast Guard during World
`War II. In this mode, the location network 50 includes
`a master transmitter MTX and two remotely located
`slave transmitters SXl and SX2 as shown in FIG. 4. In
`the LORAN location mode, the base station 30, in re
`sponse to being noti?ed that the vehicle is stolen, trans
`mits a message to the vehicle unit 10 in which the loca
`tion method is identi?ed as the LORAN location mode.
`The base station 30 will then wait until it receives loca
`tion data transmitted by the vehicle unit 10. The vehicle
`unit 10, in response to receipt of the message from the
`base station 30, will activate a LORAN receiver 18 as
`shown in FIG. 5. The LORAN receiver 18 is of a type
`corresponding to those commercially available for pri
`vate aircraft or small boats. In the LORAN system, the
`master transmitter MTX will repeatedly transmit a mas
`ter pulse signal at a known repetition rate. The two
`slave transmitters, SX1 and SC2, will also transmit slave
`pulse signals at predetermined times after the master
`pulse signal is transmitted. The delay times of the slave
`pulses are differnet so that the LORAN receiver can
`distinguish between the two. Using the well known
`LORAN algorithm, the LORAN receiver 18 will deter
`mine its geographical position with respect to the mas
`ter and salve transmitters which are stored in the vehi
`cle unit 10, then transmitted back to the base station 30.
`The base station 30 will then convert this location data
`to map coordinates.
`The stolen vehicle unit 10 may also have a alarm
`mode of operation in which, for some reason, the vehi
`cle unit 10 is no longer able to communicate with the
`base station 30. This may be caused because the vehicle
`is taken outside the range of the base station’s transmit
`ter or because the vehicle unit’s antenna or receiver is
`disabled.
`
`6
`In the operation of the stolen vehicle location system,
`the base station 30 periodically transmits a “keep alive”
`signal received by each vehicle having a vehicle unit 10.
`In response to the “keep alive” signal, the vehicle unit
`10 sets a “keep alive” timer, which will time out at a
`predetermined time which is slightly longer than the
`interval between the “keep alive” signals. As long as the
`vehicle unit 10 keeps on receiving “keep alive” signals,
`its “keep alive” timer is reset before it times out and the
`system remains passive. However, if the vehicle unit 10
`for any reason fails to receive a “keep alive” signal, its
`“keep alive” timer will time out and activate the vehcile
`unit 10 to transmit an alarm message containing the
`vehicle identi?cation number and an alarm code.
`Any vehicle within the transmission range of the
`vehicle transmitting the alarm message will receive and
`temporarily store the alarm message and set a tattle-tale
`timer. It then will wait a predetermined period of time,
`determined by the tattle-tale timer, for a response by the
`base station 30 to the alarm message. If the base station
`30 responds by sending a locate request message con
`taining the vehicle identi?cation number contained in
`the alarm message, the other vehicle units 10 temporar
`ily storing this alarm signal will dump it since they
`know the alarm message was received by the base sta
`tion 30. However, if the other vehicle units 10 do not
`receive a locate request message containing the vehicle
`identi?cation number contained in the alarm message
`before their tattle-tale timer times out, they will activate
`their own transmitter to transmit a tattle-tale message
`containing both its own vehicle identi?cation number,
`the vehicle identi?cation number contained in the alarm
`message, and a code or ?ag identifying it as a tattle-tale
`message. The base station 30 will respond to the tattle
`tale message and send a locate request message to the
`vehicle unit 10 which sent the tattle-tale message re
`questing that it transmit in one of the four location
`modes described above so that its location can be deter
`mined. Although the exact location of the vehicle gen
`erating the alarm message cannot be pin-pointed by the
`tattle-tale message, its general location and/or direction
`from the base station 30 can be determined. Further,
`since it is possible that more than one vehicle unit 10
`may transmit a tattle-tale message, the location of all of
`these vehicles may be used to help pin-point the vehicle
`transmitting the alarm signal.
`The details of the vehicle unit 10 are shown in FIG.
`5. Referring FIG. 5, the vehicle unit 10 includes a re
`ceiver 12 responsive to the messages sent by base station
`30, an electronic control unit (ECU) 14, a transmitter
`16, and the LORAN receiver 18. The vehicle unit 10
`may also contain a visual display 26 and an illegal entry
`alert detection system consisting of an illegal entry
`detector 20, an illegal entry transmitter 22, and a per
`sonal receiver 24.
`The illegal entry detector 20 may be any of the con
`ventional detectors used to detect illegal entry of the
`vehicle, such as a seat pressure sensor, a motion sensor,
`an infrared (IR) sensor, or a combination of several
`sensors. Upon the detection of an illegal entry, the ille
`gal entry detector 20 will activate the illegal entry trans
`mitter 22v to transmit a signal activating the personal
`receiver 24 to generate an audio and/or visual signal.
`The personal receiver 24 is normally carried by the
`owner or operator of the vehicle when he leaves the
`vehicle. Preferably, the personal receiver 24 can re
`spond to the signal transmitted by the illegal entry
`transmitter 22 up to 1,000 yards. Upon being alerted of
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`an illegal entry of the vehicle, the owner or operator
`will check to see if the vehicle has actually been stolen.
`If it has, he will contact the base station 30, informing an
`operator that the vehicle has been stolen and giving the
`operator the vehicle’s identi?cation number (VIN).
`This vehicle identi?cation number will then be entered
`into the base station 30, which will transmit a locate
`request message to activate the stolen vehicle’s unit 10.
`To avoid accidental activation, the base station 30 will
`transmit two identical locate request messages sepa
`rated by a ?xed time period. The vehicle unit 10 will
`only respond to the receipt of both the ?rst and second
`locate request messages within the ?xed time period.
`The ECU 14 may be a hard-wired logic control but,
`preferably, is a programmed microprocessor, such as an
`INTEC 8086 or any other comparable commercially
`available microprocessor. The ECU 14 will decode the
`?rst locate request message and set a flag indicating its
`receipt. It will then set a delay timer and wait for the
`second locate request message. Upon receipt of the
`second locate request message, the ECU 14 will activate
`the transmitter 16 or the LORAN receiver 18 in accor
`dance with the location mode contained in the message.
`If the location mode is the direction-triangulation mode,
`the transmitter 16 will transmit at the designated fre
`quency a short message stored in the ECU 14 which
`contains only its vehicle identi?cation code. The base
`station 30 will continue to transmit similar messages to
`the vehicle unit 10 each time changing the frequency of 30
`the signal to be transmitted so that it would be very
`dif?cult for the thieves to generate a signal which
`would interfere with the transmission of the transmitter
`16. The subsequent messages may also instruct the vehi
`cle unit to change the power level of its transmitted
`message as previously described.
`In a like manner, if the location method code or ?ag
`in the received message is indicative of the distance
`triangulation or distance-direction mode, the transmit
`ter 16 will await the receipt of the echo pulse transmit
`ted by the base station 30. It will then delay this echo
`pulse a precise period of time, then transmit it to the
`remotely located receivers or transmit it back to the
`base station 30; at the frequency contained in the locate
`request message.
`Finally, if the location method code or flag is indica
`tive of the LORAN mode, the vehicle unit 10 will acti
`vate its LORAN receiver 18. The LORAN receiver 18
`will then receive the transmission by the LORAN net
`work and determine its geographical location, which is
`communicated to the ECU 14 where it is stored. The
`ECU 14 will then construct a message containing the
`geographical data generated by the LORAN receiver
`18 which is transmitted back to the base station 30 by
`the transmitter 16. For these latter transmissions, the
`base station 30 will have the capabilities to compute the
`map coordinates of the vehicle from the received infor
`mation.
`The ECU 14 also includes the “keep alive” timer and
`will activate the transmitter 16 when the “keep alive”
`timer times out and output the alarm message to the
`transmitter 16 for transmission. Any alarm messages
`received by the receiver 12 from a different vehicle unit
`10 will be stored in the ECU’s memory and the tattle
`tale timer activated. A response message from the base
`station 30 before the tattle-tale timer times out will
`cause the ECU 14 to dump the stored alarm message.
`Otherwise, the ECU 14 will construct a tattle-tale mes
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`sage, as previously described, which will be transmitted
`by the transmitter 16 after the tattle-tale timer times out.
`The details of the base station 30 are shown in FIG. 6.
`Referring to FIG. 6, the base station 30 includes a base
`station electronic control unit (ECU) 32, which is capa
`ble of receiving inputs from an external source, such as
`an operator, and receive inputs from a receiver 36, and
`from the location network 50 through a modem 44. The
`ECU 32 stores the vehicle identi?cation number of each
`vehicl