CA1184610A - Intrusion alarm system for vehicles - Google Patents

Abstract

Abstract of the Disclosure An alarm system for detecting unauthorized intru-sion into a vehicle and determining the location of such vehicle includes a vehicle alarm and one or more networks for receiving the output signal from vehicle alarm. The vehicle alarm includes a transmitter for broadcasting a low frequency modulated radio frequency alarm signal at the citizen band distress frequency and a control unit for selectively activating the alarm upon a drop in the voltage magnitude of the vehicle power supply induced by an un-authorized intrusion. The various networks include citizen band radio detectors, mobile dedicated alarm detectors, and fixed dedicated alarm detectors accompanied by a display unit.

Description

INTR~SION ALARM SYST~M FOR VEHICLES

Technical Field The present invention pertains generally to an 5 alarm system for vehicles. More particularly, the present invention relates to an alarm system Eor detecting un--authorized 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 15 attempts, numerous devices have been devised to provide an alarm signal or to disable the vehicle in the event oE an unauthorized entry.
Those deterrent systems which provide an alarm utilize an audio alarm hoping to frighten the prospective 20 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 construction of 25 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 30 thief, may inadvertently 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 35 hazardous and potentially fatal situations where an authorized individual who has inadvertently failed to follow the proper procedures abruptly may have the vehicle's ignition or fuel cut off or its steering column locked during actual operation of the vehicle.

Disclosure of the Invention It is, therefore, an object oE the present inven-tion to provide an intrusion alarm and locating system for vehicles which is inexpensive and provides a radio fre-quency broadcast alarm signalO
It is a further object of the present invention 10 to provide an intrusion alarm and locating system for vehicles, 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 15 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 actua-tion of the transmitter.
These and other objects and advantages of the 20 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 system for detecting an unauthorized intrusion into a vehicle and the location of the vehicle, includes a vehicle alarm installed on the vehicle for generating a radio Erequency alarm signal upon the unauthorized intrusion into the vehicle, the radio frequency alarm signal 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, ths 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.
An individual vehicle alarm circuit for detecting an unauthorized intrusion into a vehicle includes a trans-mitter for broadcasting a radio -Erequency alarm signal, the transmitter having a modulator generating a low frequency for modulating the radio frequency alarm signal at the low 5 frequency, and a control unit for selec~,ively activating the transmitter upon an unauthorized intrusion. ~he con trol means has a voltage detector for detecting a drop in the voltage magnitude of the vehicle power supply and providing an output signai indicative thereof, a timer 10 circuit receiving the output signal from the voltage detector and providing a transmitter actuation signal to the transmitter after a first preselected time delay~ and a security switch for inhibiting the transmission oE a signal rom the timer circuit to the transmitter.
Brie Description of the Drawings Fiyu 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. ~ 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 Preerred ~mbodiment Fig. 1 illustrates a complete intrusion alarm and locating system for vehicles in accordance with the concept of the present invention, generally referred to by the numeral 10. Vehicle intrusion alarm and locating system 10 includes a vehicle alarm, one or more oE which are identi . i fied in the drawings with the numeral 11 and is installed as hereinaEter 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 5 the whereabouts of each vehicle whose vehicle alarm 11 has been activated.
Network 12 utilizes the enormous number of citizen band radios 15 existing throughout the United States as a no-cost, pervasive detection scheme. As noted 10 below, vehicle alarm 11 generates an audio mod~lated 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 net-work, it is highly desirable to select such frequency to be 15 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 con-taining an activated alarm comes into close proximity with a citizen band radio receiver tuned to channel 19, the 20 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 I~F signal from a vehicle containing an activated alarrn is extremly 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 30 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 moclulation patterns may be acceptable for use herewith.
In certain specialized applications it may be advarltageous to provide a network 13 having mobile dedi-cated alarm detectors 16 whose receivers are fixedly tuned to the ~F broadcast frequency of vehicle alarms 11.

For example, vehicles used in law enforcement operations may be 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 5 signal from any individual vehicle alarm 11 in proximity to the law enforcement vehicle, and would permit police to immediately investigate and possibly recapture stolen vehicles having an activated vehicle alarm 11 installed therein. ~etropoli~an areas having large numbers of 10 vehicles in a given geographic area may further prefer -to provide a network 14 having fixed dedicated alarm detectors 17 and a display uni-t 18. Fixed dedicated alarm detectors 17 may be inexpensive receivers tuned to channel 19 and mounted at preselected fixed locations throughout the 15 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 receptior coverage throughout 20 their jurisdictional areaO Rather than providing receivers ; which furnish an audible output signal, as shown in Fig. 2, graphical grid transponders 20 may be provided which furnish a system alarm signal for transmission via dedi-cated telephone lines or other suitable means -to a central 25 dispatch 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 30 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, 10Hz in the example herein. Upon reception of an RF signal modu-lated at 10Hz, 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 Fig. 4 to broadly include an alarm control unit 25 and a tag transmitter ~0. Alarm Control unit 25 includes voltage 5 drop detector 26, power supply filter 28~ intrusion timer 30, exit timer 31, pushbutton 32, S-R flip flop 33, relay 34, relay contact 35, and security switch 36. Voltage drop detec-tor 26, which is electrically connected to both ter-minals of vehicle battery 27, may be any of the numerous 10 well-known detectors for monitoring a voltage magnitude and providing an output signal in the event a preselected maximum allowable change in the monitored voltage magnitude is exceeded.
~lthough the negative terminal of vehicle battery 15 27 is shown as being connected to ground, and connections to be made to such terminal may hereinafter be said to be 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 25 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 timer 30 receives the output signal 30 from voltage drop detector 26 and the filtered power supply from power supply filter 28, Intrusion timer 30 may be any conventional timer providing an output signal after a preselected time delay following receipt of the output signal from voltage drop detector 26. Exit timer 31 35 receives outputs from the vehicle battery 27 and power supply filter 28 and is connected to one terminal of momen-tary contact pushbutton 32. Exit timer 31 also may be any conventional timer providing an output signal for a pre-selected time Eollowing the momentary closing of pushbutton 32.
The output signals from intrusion timer 30 and 5 exi-t 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 oppo-site ends of the coil (not shown) of a relay 34 such that 10 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-15 vidual gangs each of which may be preset to a differing number 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 20 gangs provides the desired level of protection by fur-nishing too many codes to ~uickly 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 con-nected to ground, the movable contact of the gang adjacent the output connected to the terminal of pushbu-tton 32 opposite that connected 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 ~F oscillator 47. Power gate 41 includes batteries 42, 43, resistor 44 and field-effect transistor (hereinafter referred to as F~ET) 45~ The positive terminal of battery 42 is connected -to the side of relay contact 35 also connected to security switch 36~ The negative terminal of battery ~2 is connected to the gate of 5 FET ~5. 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 ~erminal connected to the side of relay contact 35 also connected to ground.
Low frequency modulator 46 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 15 provides a modulated output signal to RF oscillator 47.
For reasons discussed hereinbefore, RF oscillator 47 should preferably be tuned to resonate at approximately 27.185 MHz, the citizen band radio distress frequency.
Having described the detailed construction of an 20 exemplary vehicle alarm 11l its operation may now be delineated. 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 25 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 in 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 after 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 opera-tion of the vehicle by an 5 authorized individual, the security switch 36 is set to its preset, confidential code. In Fig. 4, aligning the movab:le contact of each gang from left to riyht adjacent the third, seventh, ninth, and third contact position from the top, respectively, will result in both sides of relay 10 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 modula-tor 46 and RF oscillator 47. In short, security switch 36 has 15 disabled tag transmitter ~0 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 20 individual merely pushes pushbutton 32, momentarily con-necting exit timer 31 to ground and starting exit timer 31.
Exit timer 31 immediately generates and maintains an output signal which sets flip flop 33. The ~ output of flip flop 33 in turn changes state, energizing relay 34 and closing 25 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 sufficiently long to permit the authorized individual to depart the vehicle, say 120 30 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, con~idential code, completing 35 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 oE a preselected time delay generate an output signal which resets flip flop 33.
The ~ output of flip flop 33 in turn returns to its ori-ginal state, deenergizing relay 34 and reopening relay 5 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-10 entering the vehicle will trigger tag transrnitter 40. Ofcourse, 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 containing its own 15 independent power supply will immediately activate low frequency modulator 46 and RF oscillator 47 causing trans-mission of a modulated RF signal indicative of unauthorized entry.
In order to make vehicle intrusion alarm and 20 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-25 tionally incorporating a loading coil within RF oscillator47, 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 30 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 ~he : 35 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 opera-ting lifetime approximately coextensive with that of the vehicle. Nevertheless, where desired, batteries 42 and 43 5 may be selected to be of the magnetically coupled recharge-able ~ype, permitting recharging of batteries 42 and 43 within tag transmitter 40 without physical connection therewith.
Inasmuch as the present invention is subject to 10 many variations, modifications and changes ln detail, a number of which have been expressly stated herein, it is intended that all matter described throughout this entire specificatlon or shown ln the accompanying drawings be interpreted as illustrative and not in a limiting sense.
15 It should thus be evident that a device constructed according to the concept of the present invention, and equivalent thereto, will accomplish the objects of the present invention and otherwise substantially improve the art of alarm systems for detecting the unauthorized entry 20 into vehicles and the location thereof.

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Claims (6)

1. An alarm system for detecting an unauthorized intru-sion into a vehicle and the location of the vehicle, comprising:
a vehicle alarm installed on the vehicle for generating a radio frequency alarm signal upon the unauthorized intrusion into the vehicle, said radio frequency alarm signal 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 for receiving audio speech modulated signals tunable to said distress frequency in the citizen band frequency spectrum, said modulation of said radio frequency alarm signal producing a distinct and re-cognizable audio pattern detectable by said receivers over said audio speech modulated signals having sub-stantially greater field strength.

2. An alarm system, as set forth in claim 1, wherein said receivers are fixedly tuned to said distress frequency and are permanently mounted at fixed geographic loca-tions in an area of interest, and further including display means receiving notification of the reception of an alarm signal by each receiver and pictorially displaying the location of such receivers within said area of interest.

3. An alarm system, as set forth in claim 2, wherein said receivers are transponders including radio frequency detector means providing an output signal, bandpass filter means receiving said output signal from said radio frequency detector means and providing an output signal upon reception of a radio frequency signal having said very low frequency modulation, and relay means receiving said output signal from said bandpass filter means and providing a system alarm signal to said display means.

4. An alarm system for detecting an unauthorized intru-sion into a vehicle and the location of the vehicle, comprising:
a vehicle alarm installed on the vehicle for generating a radio frequency alarm signal upon a drop in the voltage magnitude of the vehicle power supply resulting from the unauthorized intrusion into the vehicle, said radio frequency alarm signal being at a distress frequency and being modulated at a low frequency, and, a plurality of receivers tunable to said distress frequency, said modulation of said radio frequency alarm signal producing a distinct and recognizable audio pattern detectable by said receivers over audio speech modulated signals having substantially greater field strength.

5. An alarm system, as set forth in claim 4, wherein said receivers are fixedly tuned to said distress frequency and are permanently mounted at fixed geographic loca-tions in an area of interest, and further including display means receiving notification of the reception of an alarm signal by each receiver and pictorially displaying the location of such receivers within said area of interest.

6. An alarm system, as set forth in claim 5, wherein said receivers are transponders including radio frequency detector means providing an output signal, bandpass filter means receiving said output signal from said radio frequency detector means and providing an output signal upon reception of a radio frequency signal having said low frequency modulation, and relay means receiving said output signal from said bandpass filter means and providing a system alarm signal to said display means.