Note: Descriptions are shown in the official language in which they were submitted.
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1.
INTRUSION ALARM SYSTEM FOR VEHICLES
TECHNICAL FIELD
The present invention pertains generally to an
alarm system for vehicles. More particularly, the present
invention relates to an alarm system for detecting unautho-
rized intrusion into a vehicle and determining the location
of such vehicle.
BACKGROUND ART
In recent times the theft of mobile vehicles such
as boats, planes, recreational vehicles, trucks and, in
particular automobiles has grown to alarming proportions.
In an attempt to reverse this trend and defeat theft
attempts, numerous devices have been devised to provide an
alarm signal or to disable the vehicle in the event of an
unauthorized entry~
Those deterrent systems which provide an alarm
utilize an audio alarm hoping to frighten the prospective
thief and/or broadcast a radio frequency alarm signal.
However, because such systems normally rely for their
power on the vehicle electrical system, it is possible to
quickly disable the same. Moreover, those systems which
broadcast a radio frequency alarm signal require the
~5 construction of extensive and costly receiving networks
and/or mobile telemetry transceivers to detect and locate
an alarm signal.
Those deterrent systems which attempt to disable
the vehicle, as by ignition or fuel cut-off, or steering
column lock-out, also may be disabled by the experienced
thief, may inadvertantly preclude the vehicle's operation
by an authorized individual, and are not capable of indi-
cating to law enforcement officials the location of the
vehicle after its successful theft. Some lock-out systems
operate after a fixed time delay, creating extremely
hazardous and potentially fatal situations where an autho-
; rized individual who has inadvertantly failed to follow
~ the proper procedures abruptly may have the vehicle's
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ignition or fuel cut off or its steering column loc~ed
during actual operation of the vehicle.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present
invention to provide an intrusion alarm and locating system
for vehicles which is inexpensive and provides a radio
frequency broadcast alarm signal.
It is a further object of the present invention
to provide an intrusion alarm and locating system forvehicles, as above, utilizing a pre~existing, extensive
alarm receiving network.
It is still a further object of the present
invention to provide an intrusion alarm and locating system
for vehicles, as above, with an independent, self-contained
transmitter power supply such that any attempt at tampering
with the intrusion alarm will result in the actuation of
the transmitter.
These and other objects and advantages of the
present invention over existing prior art forms will become
more apparent and fully understood from the following
description in conjunction with the accompanying drawings.
In general, an alarm circuit for detecting an
unauthorized intrusion into a vehicle includes a trans-
mitter for broadcasting a radio frequency alarm signal, thetransmitter including a modulator generating a low fre-
quency for modulating the radio frequency alarm signal at
the low frequency, and a control unit for selectively
activating the transmitter upon an unauthorized intrusion.
The control means includes a voltage detector for detecting
a drop in the voltage magnitude of the vehicle power supply
and providing an output signal indicative thereof, a timer
circuit receiving the output signal from the voltage detec-
tor and providing a transmitter actuation signal to the
transmitter after a first preselected time delay, and a
security switch for inhibiting the transmission of a signal
from the timer circuit to the transmitter.
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An alarm system for detecting an unauthori2ed
intrusion into a vehicle and the location of the vehicle,
includes a vehicle alarm installed on the vehicle for
generating a radio frequency alarm signal upon the unautho-
rized intrusion into the vehicle, the radio frequency alarmsignal being at a distress frequency in the citizen band
frequency spectrum and being modulated at a low frequency,
and a plurality of citizen band spectrum radio receivers
tunable to the distress frequency in the citizen band
frequency spectrum, the modulation of the radio frequency
alarm signal producing a distinct and recognizable audio
pattern detectable by the receivers over audio speech
signals having substantially greater field strength.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram of an intrusion alarm
and locating system for vehicles in accordance with the
concept of the present invention.
Fig. 2 is a block diagram of a portion of the
intrusion alarm and locating system for vehicles of Fig. 1
particularly adopted to finding and displaying the location
within a preselected geographic area of vehicles which have
had their alarm system activated.
Fig. 3 is a further detailed block diagram of the
exemplary graphical grid transponder depicted in Fig. 2.
Fig. 4 is a further detailed block diagram of the
exemplary individual vehicle alarm as depicted in Fig. 1,
showing in partial schematic form an alarm control unit and
tag transmitter.
- DESCRIPTION OF A PREFERRED EMBODIMENT
Fig. 1 illustrates a complete intrusion alarm and
locating system for vehicles in accordance with the concept
of the present invention, generall~ referred to by the
- 35 numeral 10. Vehicle intrusion alarm and locating system 10
includes a vehicle alarm, one or more of which are identi-
fied in the drawings with the numeral 11 and is installed
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as hereinafter explained in each individual vehicle to be
protected, and three distinct networks 12, 13 and 14 which
may be alternatively or simultaneously employed to detect
the whereabouts of each vehicle whose vehicle alarm 11 has
been activated.
Net work 12 utilizes the enormous number of
citizen band radios 15 existing throughout the United
States as a no-cost, pervasive detection scheme. As noted
below, vehicle alarm 11 generates an audio modulated radio
frequency (hereinafter called "RF") signal in the event of
unauthorized intrusion into the vehicle. In order to
avail this system of an inexpensive, pre-existing warning
network, it is highly desirable to select such frequency to
be the widely recognized distress frequency within the
citizen band radio spectrum, 27.185 MHz, popularly referred
to as "channel 19". In this manner, whenever a vehicle
containing an activated alarm comes into close proximity
with a citizen band radio receiver tuned to channel 19, the
audio modulated alarm signal may be heard. Inasmuch as the
majority of citizen band radios in the United States are
themselves operated mobile in vehicles, the likelihood of
detecting the RF signal from a vehicle containing an acti-
vated alarm is extremely high.
In order to uniquely identify a signal from
vehicle alarm 11, and to insure that the signal is easily
heard over other signals which may have many times its
field strength, it is highly desirable to modulate the RF
signal generated by vehicle alarm 11. The simplest yet
most effective modulation pattern found has been that of a
low audio frequency of approximately 10 Hz. Of course, it
will be appreciated that other modulation patterns may be
acceptable for use herewith.
In certain specialized applications it may be
advantageous to provide a network 13 having mobile dedi-
cated alarm detectors 16 whose receivers are fixedly tunedto the RF broadcast frequency of vehicle alarms 11. For
example, vehicles used in law enforcement operations may be
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equipped with inexpensive receivers tuned to channel 19.
Such receivers would serve the dual function of receiving
both citizen band distress signals and the alarm signal
from any individual vehicle alarm 11 in proximity to the
law enforcement vehicle, and would permit police to immedi-
ately investigate and possibly recapture stolen vehicles
having an activated vehicle alarm 11 installed therein.
Metropolitan areas having large numbers of
vehicles in a given geographic area may further prefer to
provide a network 14 having fixed dedicated alarm detectors
17 and a display unit 18. Fixed dedicated alarm detectors
17 may be inexpensive receivers tuned to channel 19 and
mounted at preselected fixed locations throughout the
geographic area of interest.
Once again by way of example, local law enforce-
ment agencies could mount fixed dedicated alarm detectors
17 upon telephone poles or other elements at suitable
intervals to provide complete reception coverage throughout
their jurisdictional area. Rather than providing receivers
which furnish an audible output signal, as shown in Fig. 2
graphical grid transponders 20 may be provided which fur-
nish a system alarm signal for transmission via dedicated
telephone lines or other suitable means to a central dis-
patch location for a display 21 to graphically present the
relative geographic location of each transponder and
visually and/or audibly distinguish those transponders 20
which are receiving an RF alarm signal.
As further detailed in Fig. 3, an exemplary
graphical grid transponder 20 may include a conventional
dedicated receiver 22 fixedly tuned to channel 19, the
detector of which provides an output signal to a conven-
tional bandpass filter 23. Bandpass filter 23 has a center
frequency set to the modulation frequency, 10 Hz in the
example herein. Upon reception of an RF signal modulated
at 10 Hz, bandpass filter 23 provides an output to a relay
24 which produces the above noted system alarm signal.
An individual vehicle alarm 11 may be seen in
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Fig. 4 to broadly include an alarm control unit 25 and a
tag transmitter 40. Alarm control unit 25 includes voltage
drop detector 26, power supply filter 28, intrusion timer
30, exit timer 31, pushbutton 32, S-R flip flop 33, relay
5 34, relay contact 35, and security switch 36. Voltage drop
detector 26, which is electrically connected to both termi-
nals of vehicle battery 27, may be any of the numerous
well-known detectors for monitoring a voltage magnitude and
providing an output signal in the event a preselected
10 maximum allowable change in the monitored voltage magnitude
is exceeded.
Although the negative terminal of vehicle battery
27 is shown as being connected to ground, and connections
to be made to such terminal may hereinafter be said to be
15 grounded, it should be emphasized that alarm system 11 is
equally suitable for use with an ungrounded or positive
grounded vehicle electrical system.
The output of vehicle battery 27 is also received
by power supply filter 28 including diode 29 and capacitor
37. The anode of diode 29 is connected to the positive
terminal of vehicle battery 27. Capacitor 37 is connected
across the negative terminal of vehicle battery 27 and the
cathode of diode 29. The cathode of diode 29 and the
negative terminal of vehicle battery 27 provide a filtered
source of operating power for the electrical components of
vehicle alarm 11.
Intrusion ~imer 30 receives the output signal from
voltage drop detector 26 and the filtered power supply from
power supply filter 28. Intrusion timer 30 may be any con-
ventional timer providing an output signal after a preselec-
ted time delay following receipt of the output signal from
voltage drop detector 26. Exit timer 31 receives outputs
from the vehicle battery 27 and power supply filter 28 and
is connected to one terminal of momentary contact pushbutton
32. Exit timer 31 also may be any conventional timer pro-
viding an output signal for a preselected time following the
momentary closing of pushbutton 32.
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The output signals from intrusion timer 30 and
exit timer 31 are respectively received by the reset and set
inputs to conventional S-R flip flop 33. The Q output signal
from flip flop 33 and the filtered positive power signal
from the cathode of diode 29 are connected to ~pposite ends
of the coil (not shown) of a relay 34 such that upon receipt
of a suitable logic level signal from flip flop 33 normally
open relay contact 35 is closed and remains closed until
flip flop 33 is reset by intrusion timer 30.
Security switch 36 includes a plurality of indi-
vidual gangs each of which may be preset to a differing num-
ber such that only when all switch gangs are switched to
their respective preset numbers will the input terminal of
security switch 36 be connected to its output terminal.
Security switch 36 may be provided with whatever number of
gangs provides the desired level of protection by furnishing
too many codes to quickly identify the proper combination.
For most applications a four gang thumbwheel switch may be
utilized as security switch 36, as depicted in Fig. 3.
Security switch 36 has its input terminal connected
to ground, the movable contact of the gang adjacent the output
connected to the terminal of pushbutton 32 opposite that con-
nected to exit timer 31, and its output terminal connected
to one side of relay contact 35. The side of relay contact
35 opposite that connected to security switch 36 is connected
to ground. The signal across relay contact 35 is the output
signal for alarm control unit 25 and provides the actuation
command to tag transmitter 40.
Tag transmitter 40 includes a power gate 41, a low
frequency modulator 46, and an RF oscillator 47. Power gate
41 includes batteries 42, 43, resistor 44 and field-effect
transistor (hereinafter referred to as FET) 45. The positive
terminal of battery 42 is connected to the side of relay
contact 35 also connected to security switch 36. The negative
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terminal of battery 42 is connected to the gate of FET 45.
Resistor 44 is connected across the gate and source of FET
45. Battery 43 has its positive terminal connected to the
source of FET 45 and its negative terminal connected to the
side of relay contact 35 also connected to ground.
Low frequency modulator ~6 may be any conven-
tional modulator suitable for modulating the power supply
to RF oscillator 47 at the selected low audio frequency.
Low frequency modulator 46 is connected to the drain of FET
45 and the negative terminal of battery 43, and in turn
provides a modulated output signal to RF oscillator 47.
For reasons discussed hereinbefore, RF oscillator 47 should
preferably be tuned to resonate at approximately 27.255
MHz, the citizen band radio distress frequency.
Having described the detailed construction of an
exemplary vehicle alarm 11, its operation may now be deli-
neated. The operation of vehicle alarm 11 may be more
readily understood if it is first appreciated that vehicle
alarm 11 is triggered by any change in the vehicle system's
voltage magnitude greater than a preselected tolerable
maximum. Inasmuch as virtually any entry to the vehicle or
attempted start of the vehicle's ignition will cause such a
change in the vehicle system's voltage magnitude as a
result of voltage drops across lights and the starter
motor, etc., such an alarm detection system is extremely
reliable. However, since an authorized individual will
also produce alarm triggering voltage drops upon entry to
and exit from the vehicle, where vehicle alarm 11 is
mounted în the interior of the vehicle for added security
some means must be provided to temporarily disable the tag
transmitter 40 while the authorized individual both enters
the car and permanently disarms vehicle alarm 11, and exits
the car a~ter arming vehicle alarm 11. Intrusion timer 30
and exit timer 31, in conjunction with their associated
circuitry, respectively provide this function during entry
and exit.
During normal operation of the vehicle by an
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authorized individual, the security switch 36 is set to its
preset, confidential code. In Fig. 4, aligning the movable
contact of each gang from left to right adjacent the third,
seventh, ninth, and third contact position from the top,
respectively, will result in both sides of relay contact 35
being shorted together. This in turn connects batteries 42
and 43 in series. The resultant gate-source voltage
effectively "pinches off" FET 45, precluding any power from
being received by low frequency modulator 46 and RF oscil-
lator 47. In short, security switch 36 has disabled tagtransmitter 40 by shorting its input leads. The setting of
the confidential code into security switch 36 may be
referred to as "disarming" vehicle alarm 11.
When the authorized individual wishes to leave
the vehicle and activate vehicle alarm 11, the authorized
individual merely pushes pushbutton 32, momentarily con-
necting exit timer 31 to ground and starting exit timer 31.
Exit timer 31 ilNnediately generates and maintains an output
signal which sets flip flop 33. The Q output of flip flop
33 in turn changes state, enersizing relay 34 and closing
normally open relay contact 35. As long as relay contact
35 remains closed tag transmitter 40 is again disabled as a
result of its shorted input leads. By presetting the exit
timer to have a delay su~ficiently long to permit the
authorized individual to depart the vehicle, say 120
seconds, no voltage drops caused by the authorized indi-
vidual in departing the vehicle will trigger tag trans-
mitter 40. As soon as pushbutton 32 is released, the
authorized individual randomly resets security switch 36 to
a code other than the preset, confidential code, completing
the "arming" of individual vehicle alarm 11.
Thereafter, if for any reason the vehicle elec-
trical system would evidence a drop in voltage magnitude,
intrusion timer 30 would at the end of a preselected time
delay generate an output signal which resets flip flop 33.
The Q output of flip flop 33 in turn returns to its origi-
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nal state, deenergizing relay 34 and reopening relay
contact 35. By presetting the intrusion timer to have a
delay sufficiently long to permit the authorized individual
to enter the vehicle and disarm the individual vehicle
alarm 11 by resetting security switch 36, say 60 seconds,
no voltage drops caused by the authorized individual in
re-entering the vehicle will trigger tag transmitter 40.
Of course, an unauthorized individual not knowing the
preset, confidential code will be unable to stop the
activation of tag transmitter 40. Moreover, should the
leads to tag transmitter 40 be cut, power gate 41 contain-
ing its own independent power supply will immediately
activate low frequency modulator 46 and RF oscillator 47
causing transmission of a modulated RF signal indicative of
unauthorized entry.
In order to make vehicle intrusion alarm and
locating system 10 as free from tampering as possible, it
has been found to be greatly desirable to enclose all
transmitter 40 components in a housing having the shape of
a thin wafer or tag, which could be sandwiched between the
vehicle's windshield layers during fabrication. By addi-
tionally incorporating a loading coil within RF oscillator
47, use of an external antenna becomes unnecessary, making
system 10 further innocuous. It has also been found that
such a configuration results in loosely coupling the RF
signal to the windshield cavity itself, many of which have
a natural resonance at approximately 30 MHz, thereby pro-
ducing further signal gain.
Tag transmitter 40 may be made to be a low power
output device, both to avoid the licensing requirements of
governmental communications regulations and to extend the
operating lifetime of batteries 42 and 43, the independent
power supply for tag transmitter 40. Given the limited
power requirements and short, if any, operational periods
of tag transmitter 40, it is likely that conventional
alkaline batteries 42 and 43 shall provide a useful
operating lifetime approximately coextensive with that of
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the vehicle. Nevertheless, where desired, batteries 42 and
43 may be selected to be of the magnetically coupled recharge-
able type, permitting recharging of batteries 42 and 43
within tag transmitter 40 without physical connection
therewith.
Inasmuch as the present invention is subject to
many variations, modifications and changes in detail, a
number of which have been expressly stated herei.n, it is
intended that all matter described throughout this entire
specification or shown in the accompanying drawings be
interpreted as illustrative and not in a limiting sense.
It should thus be evident that a device constructed accor-
ding to the concept of the present invention, and equiva-
lent thereto, will accomplish the objects of the present
lS invention and otherwise substantially improve the art of
alarm systems for detecting the unauthorized entry into
vehicles and the location thereof.
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