Vehicle security apparatus and method

An anti-theft apparatus to prevent "car jacking" includes a transmitter carried by the driver and a receiver and a switch circuit installed in the vehicle such that, when the receiver fails to detect the signal broadcast by the transmitter, the switch circuit disables the vehicle for operation. Timer circuitry is disclosed to cause the disablement only after a selected period that the broadcast signal is lost. An event detector, such as a switch circuit connected to the door light switch circuit of the vehicle, may be used to arm the disable circuit for a selected period so that disablement occurs only when the transmitter and receiver are separated beyond their communication range during a defined time interval following the occurrent of the event.

FIELD OF INVENTION 
The present invention broadly concerns protective devices and methods used 
to provide security for vehicles against theft. More specifically, the 
present invention relates to apparatus and methods that may be employed to 
protect against theft while the vehicle is in operation by causing removal 
of the operator therefrom under force or threat of force. 
BACKGROUND OF THE INVENTION 
Ever since the development of a mechanized vehicle industry, the protection 
of such vehicles against theft has been of great concern, primarily due to 
their monetary value. In an early effort to protect such vehicles, 
manufacturers installed doorlocks so that the owner could lock the vehicle 
at times when the owner was not going to be present. Likewise, 
manufacturers fairly early began installing keyed locking switches that 
were interposed in the electrical ignition system of the vehicle. In such 
systems, an ignition key is necessary to actuate such a locking switch 
which then completes the electrical circuit in the electronic ignition 
system. While these systems proved useful, thieves have learned techniques 
for circumventing such systems. 
Subsequently, manufacturers developed mechanical locking systems for theft 
prevention. One such example is an internal lock on the steering mechanism 
of the vehicle. Again, methods of circumvention were developed by those 
who wanted to steal the vehicles. Retro-fit locking appliances, such as 
Steering wheel lock bars were developed, but these proved cumbersome and 
inconvenient to use. Various electronic alarms have been employed to 
signal an alarm, such as by blowing the vehicle horn, blinking the 
vehicle's lights and/or sounding sirens, in an effort to reduce the 
likelihood of vehicle theft. 
The aforementioned techniques, whether installed by manufacturers or 
employed as retro-fit systems, address the situation of theft of the 
vehicle usually while it is not in operation and unattended. For whatever 
reason, there has been a recent increase of vehicle theft just as the 
owner is starting the vehicle or while the vehicle is in operation but 
stopped in transit. Such latter situations often may occur at a traffic 
control signal or where the operator desires to momentarily step out of 
the vehicle such as for an errand. In this type of theft, recently 
referred to as "car jacking", a thief causes the operator to exit the 
vehicle either under force or under the threat of force, and the thief 
thereafter drives away with the vehicle, the operator's ignition keys 
necessary for maintaining access and operation of the vehicle and whatever 
possessions that are in the vehicle. 
The present invention addresses the need for security systems to prevent or 
deter car jacking and employs a new and non-obvious integration of 
electronic proximity detection with electronic control circuitry of a 
vehicle. To this end, it should be understood in this description that the 
word "vehicle" could broadly encompass any motor powered transportation 
vehicle including, but not limited to, cars, trucks, boats, etc. 
Furthermore, the term "motor powered" in this context is not limited to 
vehicles powered by internal combustion engines but could include the 
developing technology of electric vehicles or other power systems as well. 
The present invention is directed to interact with the electronic control 
system of such motor powered vehicles whether it be the electronic 
ignition system of a typical internal combustion engine driven vehicle or 
any of the electronic circuitry of an electrically powered vehicle. 
As noted above, the present invention integrates proximity detection with 
the electronic control circuitry of a vehicle. As is known, proximity 
detection may utilize a transmitter which transmits a signal, such as a 
radio signal, on a selected frequency, and a receiver tuned to receive 
that frequency. In some implementations of this technology, an alarm is 
sounded when the transmitter and receiver come within a threshold distance 
of one another, and the receiver thereby receives the transmitted signal, 
in order to sound an alarm indicating such closeness. Another 
implementation of such technology contemplates the indication of an alarm 
when the transmitter and receiver are separated a distance greater than a 
threshold communication distance. 
An example of this technology is described in U.S. Pat. No. 4,260,982 
issued Apr. 7, 1981 to DeBenedictis et al. In this patent, a pulse coded 
modulation responsive alarm system is provided to produce an alarm 
whenever the distance between a transmitter and a receiver exceeds a 
predetermined distance. This patent discusses that the system may be used 
to prevent loss of luggage or theft of other objects, and the patent 
discusses pre-existing alarm circuits used, for example, with automobiles. 
The earlier systems were proned to fail due to the possible presence of 
interference signals which the receiver would sense thereby falsely 
indicating that the transmitter was in the acceptable predetermined 
distance. To solve this, the transmitter in the '982 Patent broadcast a 
signal that is pulse coded at a selected frequency at a reduced duty 
cycle. The receiver, correspondingly, is tuned to the selected frequency 
and is adjustable in sensitivity to set the predetermined range of 
operation. A timer circuit is provided which reset each time a pulse is 
detected by the receiver but, after the absence of a series of pulses, the 
timer triggers and activates an alarm. 
Other prior inventions have described alarm or electronic monitoring 
circuits which may be employed in a variety of ways. For example, U.S. 
Pat. No. 4,785,291 issued Nov. 15, 1988 to Hawthorne discloses a 
monitoring apparatus that is affixed to a person, such as a child, to be 
monitored and a receiver/monitor apparatus that may be maintained, for 
example, by a parent to monitor the movement of the child beyond a 
predetermined range. U.S. Pat. No. 4,675,656 issued Jun. 23, 1987 to 
Narcisse likewise shows an out-of-range personal monitor and alarm. U.S. 
Pat. No. 4,101,873 issued Jul. 18, 1978 to Anderson et al discloses a 
system to interrogate the position of objects to sound an audible response 
so that the object can be located. U.S. Pat. No. 4,598,272 issued Jul. 1, 
1986 to Cox likewise shows an electronic monitoring system for monitoring 
a persons whereabouts. U.S. Pat. No. 4,792,796 issued Dec. 20, 1988 to XXX 
also shows an encoded transmission signal and circuitry that generates an 
alarm for indicating failure of reception of the coded signal to monitor 
the presence or absence thereof. 
Despite the development of both the security devices described above, there 
remains a need for improved security systems which protect owners and 
operators from theft of their vehicles. There is further a specific need 
for systems which protect against or serve to deter car jacking and 
similar crimes. There is a need for such system which can be manufactured 
as original equipment on a vehicle or easily integrated with an existing 
vehicle. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a new and useful 
apparatus and method for protecting against theft of a motor-powered 
vehicle. 
Another object of the present invention is to provide an apparatus and 
method for combating forced usurpation, i.e. "car jacking", of a vehicle 
from the rightful operator. 
A further object of the present invention is to provide an apparatus and 
method for temporarily disabling a vehicle should it be improperly removed 
from the vicinity of the rightful operator. 
A still further object of the present invention is to provide an apparatus 
that may retro-fit onto the existing electronic controlled systems of 
motor powered vehicles in order to monitor the presence of the rightful 
operator and to benignly disable operation of the vehicle should the 
operator be displaced and the vehicle stolen while the vehicle is in 
operation. 
Yet another object of the present invention is to provide an inexpensive, 
reliable security system and method of protecting a vehicle which is 
simple to install on existing vehicles without interfering with the normal 
operation thereof yet which will protect against car jacking. 
According to the present invention, then, an anti-theft apparatus and 
method is described for use with motor powered vehicles. The anti-theft 
apparatus is adapted to interconnect with an electronic control circuit of 
the vehicle and is operative to selectively disrupt the control circuit to 
disable the vehicle. Broadly, the apparatus includes a transmitter which 
is adapted to be carried by a driver of the vehicle and which is operative 
to produce a broadcast signal of selected frequency. The vehicle carries a 
receiver, and this receiver is operative to receive the broadcast signal 
when the transmitter is within a communication range. When the receiver 
fails to receive the broadcast signal, when the transmitter is out of the 
communication range, the receiver operates to produce an out-of-range 
signal. A switch circuit includes a switch element that is interposed in 
the electronic control circuit of the vehicle and has a switch active 
state wherein said control circuit is operative so that the vehicle is 
enabled and a switch inactive state wherein the control circuit is 
disrupted to disable the vehicle. A switch control circuit is provided and 
operates in response to the out-of-range signal to cause the switch 
element to change from the switch active state to the switch inactive 
state. 
Preferably, the anti-theft apparatus includes timer circuitry associated 
with the receiver so that the out-of-range signal is produced only after 
the receiver fails to receive the broadcast signal for a selected time 
duration, for example, approximately five seconds. Furthermore, it is 
preferred that the anti-theft apparatus includes an event detector 
operative to sense the occurrence of a selected event, such as the opening 
of a door of the vehicle, and produces an arming signal in response to the 
occurrence. The switch control circuit is then operative in response to 
the out-of-range signal to cause the switch element to change from the 
switch active state to the switch inactive state only when the arming 
signal is present. In this case, the event detector includes a time out 
circuit operative to discontinue the arming signal following a time 
interval after the occurrence of the event, and this time interval may be 
selected to be in the range of two to ten minutes. Here, also, the event 
detector may be electrically connected to a standard door monitoring 
circuit provided in the vehicle. In any event, the switch control circuit 
preferably operates to lock the switch element in a switch inactive state 
in response to the out-of-range signal, and a reset circuit is provided in 
order to be selectively actuated to unlock the switch element from the 
switch inactive state. 
The broad method according to the present invention, therefore, 
contemplates the method of protecting a motor vehicle from theft 
accomplished by usurping operation of the vehicle from an operator 
thereof, displacing the operator out of the vehicle and removing the 
vehicle away from the operator. Here, the method is that method which is 
implemented by the above-described apparatus, and the method includes a 
first step of providing first means carried by the operator of the vehicle 
and second means carried by the vehicle with said first and second means 
for detecting a distance of separation between the operator and the 
vehicle. A second step includes the interposition of a switch element in 
the electronic control circuit of the vehicle wherein the switch element 
has a switch active state whereby the control circuit is operative and a 
switch inactive state whereby the control circuit is disrupted. Finally, 
the method includes the step of monitoring the distance of separation 
between the operator and the vehicle and changing the switch element from 
the switch active state to the switch inactive state when a distance of 
separation exceeds a threshold distance. 
This broad method may include the step of changing the switch element from 
the switch active state to the switch inactive state only after the 
distance of separation has exceeded the threshold distance continuously 
for a selected time duration. The broad method may also include the step 
of monitoring for an occurrence of a selected event and wherein the step 
of changing the switch element from the switch active state to the switch 
inactive state occurs only if the distance of separation exceeds the 
threshold distance within a selected interval of time following occurrence 
of the selected event. This selected event, then, is preferred to be the 
opening of a door, and the method includes the step of interconnecting a 
detector element to the door monitoring circuit of the motor powered 
vehicle. 
These and other objects of the present invention will become more readily 
appreciated and understood from a consideration of the following detailed 
description of the preferred embodiment when taken together with the 
accompanying drawings, in which:

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
The present invention is directed to providing an anti-theft apparatus and 
method adapted for use with standard motor powered vehicles in order to 
prevent or deter theft of such vehicles. The apparatus is constructed so 
that it may be included as original equipment with a vehicle during 
manufacturer or which may be easily and cheaply retro-fitted onto an 
existing vehicle. In either event, the apparatus and method concerns the 
interrupting of an electronic control circuit of the vehicle in order to 
disable the vehicle in the event of theft, and particularly, car jacking. 
To this end, it should be understood that the electronic control circuit 
of the vehicle may be the ignition circuit for an internal combustion 
engine driven vehicle or any electrical power circuit for an electric 
vehicle, and the like. 
A block diagram of a first exemplary embodiment of the present invention, 
and in this instance the preferred embodiment, is shown in FIG. 1, 
although it should be appreciated that modification of the particular 
selected circuit may be made without departing from the scope of this 
invention. In FIG. 1, it may be seen that anti-theft apparatus 10 includes 
a transmitter 12 having an antenna 13 and a receiver 14 having an antenna 
15. Receiver 14 includes a receiver unit 16 connected to antenna 15 and a 
signal loss timer 18 operative to receive signals from receiver unit 16. 
Transmitter 12 operates to produce a broadcast signal of a selected 
frequency as represented by broadcast signal "S". Receiver 14 operates to 
receive the broadcast signal at input 17. To this end, as described more 
thoroughly below, receiver unit 16 process analog signal "S" to produce a 
digital pulse signal that is counted by signal loss timer 18 so that, in 
the event that receiver 14 looses the broadcast signal for a selected time 
interval, signal loss timer 18 produces an "out-of-range" signal at output 
20. Transmitter 12 is adapted to be carried by a driver of the vehicle 
while receiver 14 is adapted to be mounted to or carried in the vehicle 
and is operative to receive the broadcast signal when transmitter 12 is 
within a communication range of the receiver 14. 
An event detector is provided and is operative to sense the occurrence of a 
selected event and to produce an arming signal in response to that 
occurrence. For example only, as is shown in FIG. 1, the occurrence to be 
sensed is the opening of a selected door of the vehicle. To this end, 
anti-theft apparatus 10 includes a detector circuit 30 having a door open 
detector sub-circuit 32 which produces an arming signal at output 34 when 
the event, such as the opening of the vehicle door, occurs. The arming 
signal is presented to a time out sub-circuit 36 which acts to present the 
arming signal to an inverter 38 which forms part of detector circuit 30. 
A switch control circuit 50 includes a logic element 52 that is operative 
to receive both the out-of-range signal from output 20 and the inverted 
arming signal from output 40 from inverter 38. The arming signal from time 
out sub-circuit 36 may be presented to an arm alarm 54 while the 
out-of-range signal may be presented to a signal loss alarm 56 as shown in 
this Figure. Alarms 54 and 56 may be audio alarms, visual displays, 
indicator lights or the like. In any event, logic element 52 acts to sense 
the presence of both the arming signal and the out-of-range signal to 
produce a control signal at output 58 thereof. Control signal 58 is 
presented to input 62 of flip-flop element 60 which, upon receipt of the 
control signal at input 62 produces a disable signal at output 64 thereof. 
If desired, the presence of a disabled signal may be presented to a 
disable alarm 66 which again may be an audio, visual or other indicator 
alarm. In any event, the disable signal from output 64 of flip-flop 60 is 
presented to a disable sub-circuit 68 that is operative to drive a control 
circuit switch 80 that is interposed in the control circuit of the 
vehicle. Control circuit switch 80 is normally biased into an active state 
wherein the electronic control circuit of the vehicle is enabled. However, 
upon receipt of the disable signal from flip-flop 60, disabled sub-circuit 
68 causes a control circuit switch to move into an inactive state which 
disrupts the electronic vehicle control circuit 80 of the vehicle thereby 
disabling operation of the vehicle. 
The block diagram circuit of FIG. 1 may be simply implemented by the 
electronic circuitry shown in FIG. 2. Here, it may be seen that door open 
detector 32 is connected to the door monitoring circuit 100 of a standard 
vehicle. To this end, it should be understood that this door monitoring 
circuit includes a door switch that normally in an open state but, when 
the door opens, the door switch activates, for example, to light the 
interior compartment of the vehicle by means of door or overhead lights. 
This circuit may also include a "door ajar" alarm to advise the operator 
that the door is not completely closed. The door monitoring circuit of 
most vehicles is powered at 12 volts and, when the door is opened, the 
switch connects the circuit to ground. Accordingly, the door open detector 
sub-circuit of the present invention includes a resistor 102 and a diode 
104 connected in series between a positive voltage source V.sup.+, and a 
door monitoring circuit 100. When the door monitoring circuit 100 is not 
activated, the connecting point 106 between resistor 102 and diode 104 is 
at voltage V.sup.+ ; however, when door monitoring circuit is activated, 
the negative side of diode 104, as indicated at location 108, goes to 
ground thereby causing location 106 to switch from voltage V.sup.+ to 
ground potential. 
Time out sub-circuit 36 includes a timer element 110 which may be standard 
"555" circuit device as known in the art, but is preferably 1/2 of a 
standard "556" microcircuit, again as known in the art. To this end, pin 6 
of the circuit chip 110 is pulled to ground when door monitoring circuit 
100 becomes activated which causes chip 110 to produce a positive voltage 
signal at location 112 corresponding to pin 5 of circuit chip 110. This 
positive voltage signal thus defines the "arm" signal and last for a 
duration that is set by resistor 114 and capacitor 116. Here, it may be 
seen that pins 1 and 2 of circuit chip 110 are interconnected and are 
connected voltage V.sup.+ through resistor 114 and to ground through 
capacitor 116. Resistor 114 and capacitor 116 thus form an RC circuit 
defining the time constant for timer circuit chip 110. Resistor 114 and 
capacitor 116 may be selected as desired, but it is preferred that they be 
selected to provide a time interval for the arm signal that is between 
approximately two and ten minutes. The arm signal is then presented to 
input 37 of inverter 38 so that an inverted arm signal may be outputted at 
output 40 at inverter 38. A light emitting diode 154 is connected in 
series with resistor 118 to ground so that, when the positive voltage 
alarm signal is present at output 112, diode 154 activates to define the 
arm alarm 54 described with respect to FIG. 1. 
Resistor 118 and diode 154 form part of switch control circuit 50 which 
includes an OR gate 152 that defines logic element 52, also described with 
respect to FIG. 1. As noted above, the out-of-range signal for receiver 14 
is outputted at 20, and this out-of-range signal is presented to OR gate 
152 at a second input 153 thereof. Light emitting diode 156 is connected 
between input 153 of OR gate 152 and ground so that the presence of the 
out-of-range signal causes light emitting diode 156 to activate, thus 
defining the signal loss alarm 56 described with respect to FIG. 1. 
Receiver 14 is constructed so that when it is receiving the broadcast 
signal from transmitter 12 , receiver 14 outputs a positive voltage at 
potential V.sup.+. However, should a loss of the broadcast signal occur 
for longer than a selected duration, receiver 14 produces a logic "low" 
corresponding to ground potential so that input 153 goes to ground, in 
such event. The output 158 of OR gate 152 therefore is high, that is 
voltage V.sup.+, if either of inputs 151 or 153 are at a logic high. 
However, if both of inputs 151 and 153 are at a logic low, output 158 is 
at a logic low. The output of OR gate 152 is presented to flip-flop 60 
which, is as seen in FIG. 2, comprises a second half of the standard "556" 
circuit chip 110. Accordingly, input 62 of flip-flop 60 corresponds to pin 
8 of circuit chip 110, and flip-flop 60 has an output 64 at pin 9 . Output 
64 is at ground potential in the normal state, that is, when input 62 is 
at a logic high. However, when a logic low is inputted at input 62, 
flip-flop 60 changes its output from a logic low to a logic high and 
remains in that state until reset. To accomplish this, pins 7 and 12 of 
circuit chip 110 are interconnected to one another and to ground. 
The disable sub-circuit 68 is provided by resistor 120, transistor 122 and 
relay switch 124 which is interposed in the vehicle control circuit 80. 
When output 64 of flip-flop 60 goes to positive voltage, that is, to the 
logic high, transistor 122 becomes conductive to ground thereby allowing 
light emitting diode 166 to activate and define disable alarm 66 described 
with respect to FIG. 1. Relay switch 124 is connected between the 
vehicle's power circuit, normally at 12 volts and to transistor 122. Thus, 
when transistor 122 becomes conductive, current can flow through relay 
switch 124 to ground. Relay switch 124 is selected to be of a type that is 
biased into the switch active state that, despite its interposition in the 
electronic control circuit of the vehicle, acts to allow normal operation 
of the vehicle. However, when transistor 122 becomes conductive, relay 
switch 124 places its switch portion in an inactive state thereby 
disrupting the control circuit of the vehicle and thus causing the vehicle 
to become disabled. 
The vehicle will remain disabled until the circuit is reset by means of 
reset circuit 82 which includes a resistor 126 and a capacitor 128 
connected between pin 4 of circuit chip 110 and ground. Pin 14 is 
connected to voltage V.sup.+, and pin 10 of circuit chip 110 is connected 
at location 130 between resistor 126 and capacitor 128. A momentary switch 
132 is interposed between pin 14 and voltage V.sup.+ and is normal biased 
into a conductive state but may be momentarily opened to interrupt power 
to pin 14. When switch 132 is opened, pins 4, 10 and 14 of circuit chip 
110 are discharged to ground through capacitor 128. This creates a logic 
low at these pins. When switch 132 then closes, pins 4, 10 and 14 power up 
through the logic high when capacitor 128 charges. This then resets 
flip-flop 60 and signal loss timer 18. 
With respect to the circuit shown in FIG. 2, the following component table 
is provided to define the values selected according to this exemplary 
embodiment of the present invention: 
TABLE I 
______________________________________ 
Value Value 
Resistors (ohm) Capacitors 
(micro farads) 
______________________________________ 
102 10K 116 10 
114 10 Meg 128 .1 
118 470 
120 100 
126 10K 
______________________________________ 
It should be understood that the ordinarily skilled circuit designer may 
make modification to the components and values thereof in order to adjust 
the parameters of the above described circuitry without departing from the 
scope of this invention. 
Transmitter 12 is preferably of a standard, low power battery type, which 
may be conveniently carried in the pocket of the operator. This 
transmitter may, for example, operate on a carrier frequency in the range 
of slightly over 312 MHz which is the carrier frequency the type commonly 
used for garage door openers. The broadcast signal is shown in FIG. 3 as 
signal 200 where it may be seen that broadcast signal 200 is a series of 
pulse packets 202 each formed as a plurality of pulse bursts such as pulse 
burst 204 having the carrier frequency. Pulse packets 202 are spaced at 
one second intervals while pulse bursts 204 may have a coded pattern so 
that the receiver and transmitter may be coded such that receiver 14 only 
responds to the broadcast signal of transmitter 12. Receiver 14 converts 
pulse burst 204 into digital bursts 214 which are organized in digital 
packets 212 as is shown for signal 210 in FIG. 3. This signal is then 
converted into signal 220 which comprises digital packets 222 appearing as 
a pulse train having a frequency of one second. Pulse bursts 214 
preferably have a frequency of approximately 700 Hz while each of pulse 
packets 202, 212 and 222 have a pulse width of approximately 20 
millseconds. Signal 220 is presented to signal loss timer which monitors 
the presence and absence of pulse packets 222. The signal loss alarm 
signal is then outputted, at output 20, for example, when five consecutive 
pulse packets 220 are missing. 
The interaction of the arm signal, the out-of-range signal and the disable 
signal is best diagrammed in FIG. 4. Here, a representative arm signal is 
shown as signal 250 which is shown to be in a logic high, that is, at a 
positive 5 volts, at time "zero" and remains at this state until five 
minutes have passed. At the five minute mark, the operator opens the door 
so that the door open detector circuit is pulled to a logic low, at the 
five minute interval. This logic low, designated 252, lasts for the time 
interval set by resistor 114 and resistor 116 for the RC time constant of 
the time out sub-circuit 36. Thus, at the ten minute mark, the alarm 
signal 250 returns to a logic high, designated at 254, for a ten minute 
interval. At the twenty minute mark, the operator again opens the door so 
that the alarm signal is inverted to a logic low, again for a five minute 
interval as represented at 256. After the time out, at the twenty-five 
minute mark, the signal again inverts to a logic high. 
A representative out-of-range signal 260 is diagrammed in FIG. 3 to occur 
contemporaneously with the example of alarm signal 250. Here, for 
approximately twelve minutes, until point 261, the transmitter and the 
receiver remain in range of one another but, at that interval, it may be 
seen that the transmitter and receiver are separated beyond the 
communication range so that receiver 14 generates a logic low signal for a 
period of approximately six minutes, until the eighteen minute mark when 
the transmitter and receiver again come within range. This corresponds to 
logic low 262. The out-of-range signal remains at a logic high, as 
represented at 264, until the twenty-four minute mark when again the 
transmitter and receivers are separated a distance further than the 
communication range so that the out-of-range signal is pulled to a logic 
low. 
Finally, with reference to FIG. 4, it may be seen that the disable signal 
remains constant, at a logic low, until the twenty-four minute mark 
notwithstanding the changes between the alarm signal and the out-of-range 
signal. However, at the twenty-four minute mark, the out-of-range signal 
goes to a logic low concurrently with the time out interval of the alarm 
signal. This corresponds to the vehicle door opening and the separation of 
the transmitter and the receiver within four minutes following the opening 
of the door. Upon simultaneous occurrence of the two logic lows, the OR 
gage 152 generates a logic low which toggles flip-flop 60 to generate a 
logic high activating the disable signal to disrupt the electronic control 
circuit of the vehicle and disable the vehicle from operation. This state 
would continue until the reset circuit, or activated, as described above. 
From the foregoing, it may be seen that in real life, this situation might 
be one where an operator got out of his/her vehicle at the five minute 
mark, for example to get gasoline. The operator made his/her purchases 
during the five minute interval and inadvertently left the transmitter on 
the counter of the station. After driving off, at the twelve minute mark, 
the operator drove a short distance and, upon observing the out-of-range 
signal realized that he/she had left the transmitter at the station 
returned at the eighteen minute mark. At this point, a theft accosted the 
driver, at the twenty minute mark, and forced him/her to exit the vehicle 
which again armed the system. The theft then drove away with the vehicle 
and went out-of-range at the twenty-four minute mark, at which time the 
vehicle became disabled thereby thwarting the theft. 
It should be appreciated from the foregoing scenario, that the sole 
presents of the out-of-range signal or the door open signal will not 
activate the vehicle disable system. However, in the usual event an 
operator is accosted at a traffic signal or other location while the 
vehicle is in operation, the operator will be forced out of the vehicle 
thereby arming the system at which time the theft will immediately drive 
off which result in a disabling of the vehicle. 
A representative transmitter circuit 12 is shown in block diagram form, in 
FIG. 5, and in schematic in FIG. 6. In FIG. 5, it may be seen that 
transmitter 12 primarily comprises a Hartley magnetic dipole transmitter 
28 which is driven by a square-wave generator 22, a positive going edge 
detector 24 and a gated square-wave generator 26. Square-wave generator 22 
operates to produce a square-wave having a frequency of 0.1 hertz. That 
is, square-wave generator 22 produces a voltage pulse every ten seconds, 
and this pulse is presented to positive going edge detector 24. Going edge 
detector 24 responds to the occurrence of each pulse to produce a pulse 
having a duration of approximately 0.1 seconds so that the resulting 
signal is a pulse train wherein each pulse has a pulse width of 0.1 
second, and where a pulse occurs every ten seconds. This pulse is then 
presented to a gated square-wave generator 26 which modulates the pulses 
at a selected frequency; this frequency is preferably approximately 700 
hertz. This pulse is then presented to the Hartley magnetic dipole 
transmitter 28 so that is operative to switch and off the transmitter with 
a modulation frequency of 700 hertz for a period of 0.1 seconds at ten 
second intervals. 
The schematic circuitry for transmitter 12 is shown in FIG. 6. Here, four 
nand gates are connected in series as is shown at 301, 302, 303 and 304. 
Preferably, this four nand gates are a single circuit element, such as a 
74HC00 CMOS quad nand gate, which is divided to form two oscillators. Nand 
gate 301 acts as the square-wave generator 22 and produces a square-wave 
having a period determined by the values of resistor 310 and capacitor 
311. Resistor 310 is selected to have a value of approximately ten megohm 
and capacitor 311 is selected to have a capacitance of 0.33 micro farad so 
that resulting period is approximately ten seconds. The duration of this 
pulse is controlled by resistor 312 and capacitor 313 which are 
effectively selected to have values of approximately ten megohms and 0.01 
micro farads. Thus, the duration of the pulse is approximately 0.1 
seconds, thus providing a duty cycle of approximately 1%. Nand gates 303 
and 304 form the gated square-wave generator 26 and act to modulate the 
pulse from nand gates 301, 302 at a frequency determined by resistor 314 
and capacitor 315. Resistor 314 is selected again to have a resistance of 
approximately ten megohm while capacitor 315 is selected to have a 
capacitance of approximately forty-seven pico farad so that resulting 
modulation frequency is approximately 700 hertz. This signal is fed 
through resistor 320 to a transistor 322 and is part of the Hartley 
magnetic dipole transmitter. Resistor 320 preferably has a resistance of 
approximately 100K ohms and transistor 322 may be any suitable transistor, 
such as that designated 2N3904. The emitter of transistor 322 is connected 
to ground through resistor 330 which may be 150 ohms while the collector 
of transistor 322 is connected to one side of a magnetic dipole 
transmitter coil 350. The base of transistor 322 is connected to the 
opposite side of transmitter coil 350 through a capacitor 324 that has a 
value of approximately 5 pico farads. Furthermore, a variable capacitor 
340 is connected across magnetic dipole transmitter coil 350 and varies in 
a value of approximately 1-10 pico farads. Furthermore, magnetic dipole 
transmitter coil 350 is connected to positive voltage through a coil 360 
having a value of 0.25 microhenries. The circuit of FIG. 6 may be placed 
on a printed circuit board, as is known in the art. Magnetic dipole 
transmitter coil 350 may then be actually a printed circuit board trace 
and should have a diameter of approximately 5/8 of an inch (.about.1.6 
centimeters). Accordingly, transmitter 12 will produce a broadcast signal 
200 of the type described with the respect to FIG. 3. 
A representative receiver block diagram is shown in FIG. 7, and in 
schematic in FIG. 8. Here, it should be understood that a variety of 
different receivers and/or transmitters could be implemented with the 
present invention so that the electronic circuitry described herein is by 
way of representation only. Indeed, circuitry, such as that disclosed in 
various patents described in the background of this invention, could be 
implemented as a component of the present invention without departing from 
the inventive scope. 
In FIG. 7, then, it may be seen that receiver 14 broadly includes a signal 
detector 42 which receives at antenna 15 a broadcast signal generated by 
transmitter 12 when transmitter 12 is within the predetermined range. 
Signal detector 42 could, for example, be a super regenerative detector 
that decodes the signal similar to pulse train 220 shown in FIG. 3. This 
signal is then presented to audio amplifier 44 which amplifies the 
detected signal and the amplified pulse train is then presented to pulse 
counter 46 which senses the presence or absence of voltage pulses. So long 
as the pulses are present, no alarm signal is generated; however, when 
pulse counter 46 fails to detect pulses for a defined time interval, as 
measured by a sequence of the pulses, pulse detector 46 generates the 
out-of-range signal 20 which may be presented to the signal loss alarm 56 
and the logic element 52, as described above. 
One very useful circuit for receiver 14 is shown in FIG. 8. It is believed 
that this circuit is understandable to the ordinarily skilled person in 
the electrical engineering field when taken in conjunction with the 
following table which sets forth a preferred circuit elements. 
TABLE II 
______________________________________ 
Resistors 
Value Value 
Element (ohm) Element (ohm) 
______________________________________ 
410 82K 419 5.6K 
411 27K 420 7.5K 
412 1.5K 421 15K 
413 27K 422 1M 
414 5.6K 423 1M 
415 330K 424 10M 
416 0-1 Meg 425 470K 
417 15K 426 5.6K 
418 1M 427 510 
______________________________________ 
Capacitors 
Value Value 
Element (micro farad) 
Element (micro farad) 
______________________________________ 
430 .000033 438 .01 
431 .001 439 .022 
432 .01 440 .01 
433 .022 441 .00047 
434 .001 442 2.2 
435 .01 443 .01 
436 .022 444 33 
437 .01 445 .000013 
______________________________________ 
Transistors 
Element Part No. 
______________________________________ 
460 C 1730 NPN 
416 H 9015 PNP 
______________________________________ 
Diodes 
Element Part No. 
______________________________________ 
490 IN4148 
491 IN4148 
492 IN4148 
______________________________________ 
Furthermore, inverters 470-475 are preferably provided by a single hex 
inverter 4069UB and nor gates 480-483 are provided by a single quad nor 
gate 4001B. Loop 450 is the receiving antenna that is electrically and 
magnetically coupled to tuning tank loop 451. The antenna preferably is a 
"C-shaped" loop printed on the circuit board with an OD of 5/8 inch and an 
ID of 3/8 inch with a gap of 1/16 inch. Loop 452 is a choke valued at 
approximately 0.02 microhenries. Crystal 500 is provided in parallel to 
loop 453. 
An alternative embodiment of the present invention, in a more simplified 
form, is shown in FIG. 9. Here, a signal S' is generated by transmitter 
512 with signal S' being received by receiver 514 which includes a signal 
loss timer 518. Signal loss timer 518 generates an out-of-range signal 520 
when the distance "d'", exceeds a preselected threshold distance of 
detection of signal S' by receiver 514. Here, however, rather than 
utilizing an event detector in conjunction with the absence of the 
detected signal, failure of receiver 512 to receive signal S' after a 
selected interval, such as a series of counted lost pulses, causes a 
disabled relay to activate directly. Disabled relay 530 thus directly 
responds to out-of-range signal 520 to interrupt the vehicle ignition 
system 580. Thus, in this embodiment, as soon as the vehicle carrying 
receiver 514 travels a distance greater than the predetermined threshold 
distance d', the vehicle is disabled and cannot be restarted until such 
time as that transmitter 512 is brought back within range. 
Based on the foregoing, it should be understood that the general method 
according to the present invention contemplates the protection of a motor 
vehicle wherein the theft is accomplished by usurping the operation of the 
vehicle from an operator by displacing the operator out of the vehicle and 
removing the vehicle away from the vicinity of the operator. In this 
method, it is necessary that the vehicle be motor powered and include an 
electronic control circuit that allows the vehicle to function and 
disables the vehicle when disrupted. The broad method includes several 
steps, the first of which is the providing of a first means carried by the 
operator of the vehicle and a second means carried by the vehicle with the 
first and second means for detecting a distance of separation between the 
operator and the vehicle. Preferably, the first and second means are 
respectively a transmitter and a receiver which are coded to communicate 
with one another within a selected communication range so that the 
receiver generates an out-of-range signal when the separation range is 
exceeded. Preferably this occurs after a distance of separation has 
exceeded the threshold distance continuously for a selected time duration. 
Returning to the general mode of methodology, a second step then 
contemplates interposing a switch element in the control circuit of the 
vehicle or in the switch element has as switch active state whereby the 
control circuit remains operative and a switch inactive state whereby the 
control circuit is disrupted to disable the vehicle. The third step of a 
general method includes the monitoring of the distance of separation 
between the operator and the vehicle and changing said switch element from 
the switch active to the switch inactive state when the distance of 
separation exceeds the threshold distance. This broad methodology may also 
include the step of monitoring for an occurrence of a selected event, such 
as a door opening, and wherein the step of changing the switch element 
from the switch active state to the switch inactive state occurs only if 
the distance of separation exceeds the threshold distance within a 
selected interval of time following occurrence of the selected event. 
Accordingly, the present invention has been described with some degree of 
particularity directed to the preferred embodiment of the present 
invention. It should be appreciated, though, that the present invention is 
defined by the following claims construed in light of the prior art so 
that modifications or changes may be made to the preferred embodiment of 
the present invention without departing from the inventive concepts 
contained herein.