# Patent

## Title
Vehicle locating unit with input voltage protection

## Abstract

A vehicle locating unit with a receiver for receiving a signal from a network of communication sources, a transponder activated when a communication source sends a message to the receiver, and a power supply regulating circuit for regulating a nominal input voltage and powering the receiver and the transponder. A protection circuit is responsive to an injected input voltage and configured to clamp the injected (high level) input voltage at a predetermined maximum voltage.

## Background
FIELD OF THE INVENTION
This invention relates to stolen vehicle recovery systems and in particular to a vehicle locating unit with input voltage protection.
BACKGROUND OF THE INVENTION
The applicant's successful and popular vehicle recovery system sold under the trademark LoJack® includes a small electronic vehicle locating unit (VLU) with a transponder hidden within a vehicle, a private network of communication towers each with a remote transmitting unit (RTU), one or more law enforcement vehicles equipped with a vehicle tracking unit (VTU), and a network center with a database of customers who have purchased a VLU. The network center interfaces with the National Criminal Information Center. The entries of that database comprise the VIN number of the customer's vehicle and an identification code assigned to the customer's VLU.
When a LoJack® product customer reports that her vehicle has been stolen, the VIN number of the vehicle is reported to a law enforcement center for entry into a database of stolen vehicles. The network center includes software that interfaces with the database of the law enforcement center to compare the VIN number of the stolen vehicle with the database of the network center which includes VIN numbers corresponding to VLU identification codes. When there is a match between a VIN number of a stolen vehicle and a VLU identification code, as would be the case when the stolen vehicle is equipped with a VLU, and when the center has acknowledged the vehicle has been stolen, the network center communicates with the RTUs of the various communication towers (currently there are 130 nationwide) and each tower transmits a message to activate the transponder of the particular VLU bearing the identification code.
The transponder of the VLU in the stolen vehicle is thus activated and begins transmitting the unique VLU identification code. The VTU of any law enforcement vehicles proximate the stolen vehicle receive this VLU transponder code and, based on signal strength and directional information, the appropriate law enforcement vehicle can take active steps to recover the stolen vehicle. See, for example, U.S. Pat. Nos. 4,177,466; 4,818,988; 4,908,609; 5,704,008; 5,917,423; 6,229,988; 6,522,698; and 6,665,613 all incorporated herein by this reference.
A typical VLU includes, inter alia, a receiver or a receiver and a transmitter combined as a transceiver, a transponder, and a microcontroller programmed to, among other things, control the operation of the transceiver and transponder to process messages received by the transceiver and to store the unique identification number of the VLU. A VLU power supply unit receives a nominal 12 volt signal from the vehicle and filters and regulates that input voltage to provide the appropriate voltage levels for the operation of the transceiver, the transponder, and the microcontroller.
When a vehicle is stolen, it is possible to disable the VLU by injecting into it a very high (e.g., 200 volt) input voltage. When subjected to such an input voltage, the power supply unit, the transceiver, the transponder, and/or the microcontroller (or individual components thereof) can be damaged rendering the VLU inoperable and unable to transmit the transponder signal.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a vehicle locating unit for a stolen vehicle recovery system which is not damaged if a high input voltage is injected into the vehicle locating unit.
The subject invention results from the realization that by adding a protection circuit to the power supply regulating circuit of the vehicle locating unit which clamps the input voltage at a predetermined maximum voltage, attempts to disable the vehicle locating unit by injecting a high input voltage into the vehicle locating unit will fail.
The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.
The subject invention features a vehicle locating unit with a receiver for receiving a signal from a network of communication sources, a transponder activated when a communication source sends a message to the receiver, and a power supply regulating circuit for regulating a nominal input voltage and powering the receiver and the transponder. A protection circuit is responsive to an injected (high level) input voltage and configured to clamp the injected input voltage at a predetermined maximum voltage.
Typically, every component of the protection circuit is selected to withstand an injected input voltage greater than said nominal input voltage. In one preferred embodiment, the protection circuit includes a voltage limiting diode which clamps the injected input voltage at the predetermined maximum voltage.
In one example, the protection circuit is integrated with the power supply regulating circuit. For example, one typically power supply regulating circuit includes a filtering circuit connected to the input voltage and a first stage voltage regulating circuit connected to the filtering circuit. The protection circuit is integral with the filtering circuit and the first stage voltage regulating circuit and every component of the filtering circuit is selected to withstand, without damage, an injected input voltage greater than said nominal input voltage. In this embodiment, it is the first stage voltage regulating circuit which includes a voltage limiting diode to clamp the output of the filtering circuit to the predetermined maximum. A second stage voltage regulating circuit is connected to the first stage voltage regulating circuit and is configured to provide the appropriate voltage levels to the receiver and transponder.



BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
FIG. 1 is a block diagram depicting the primary components associated with one example of stolen vehicle recovery system in accordance with the subject invention;
FIG. 2 is a block diagram showing the primary components associated with an embodiment of a vehicle locating unit in accordance with the subject invention; and
FIG. 3 is a circuit diagram showing the protection circuit for the power supply unit for the vehicle locating unit shown in FIG. 2.



DISCLOSURE OF THE PREFERRED EMBODIMENT
Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
As discussed in the background section above, the applicant's successful and popular vehicle recovery system sold under the trademark LoJack® includes a small electronic vehicle locating unit (VLU) 10, FIG. 1 with a transponder 12 hidden within a vehicle 14, a private network of communication towers 16 each with a remote transmitting unit (RTU) 18, one or more law enforcement vehicles 20 equipped with a vehicle tracking unit (VTU) 22, and network center 24.
When a LoJack® product customer reports that her vehicle has been stolen, the VIN number of the vehicle is reported to law enforcement center 26 for entry into database 28 of stolen vehicles. Network center 24 includes software that interfaces with database 28 of law enforcement center 26 to compare the VIN number of the stolen vehicle with database 30 of network center 24 which includes VIN numbers corresponding to VLU identification codes. When there is a match between a VIN number of a stolen vehicle and a VLU identification code, as would be the case when stolen vehicle 14 is equipped with VLU 10, network center 24 communicates with the RTUs 18 of the various communication towers 16 and each tower transmits a message to activate transponder 12 of VLU 10 bearing the particular identification code.
Transponder 12 of VLU 10 in stolen vehicle 14, once activated, begins transmitting a unique VLU identification code. VTU 22 of law enforcement vehicle 20 proximate stolen vehicle 14 receives this VLU transponder code and, based on signal strength and directional information, the appropriate law enforcement vehicle can take active steps to recover stolen vehicle 14.
Vehicle locating unit or VLU 10, FIG. 2 includes, inter alia, a receiver or a receiver and a transmitter combined in transceiver 40, transponder 42, and microcontroller 44 programmed to control the operation of transceiver 40 and transponder 42, to process messages received by transceiver 40, and to store the unique identification number of the VLU.
VLU power supply unit 50 receives a nominal 12 volt signal from vehicle 14, FIG. 1 and filters and regulates that nominal input voltage to provide the appropriate voltage levels for the operation of transceiver 40, FIG. 2, transponder 42, and microcontroller 44.
Transceiver 40 receives via antenna 11, FIGS. 1 and 2 signals from towers 16 of the network. When vehicle 14 is reported stolen by law enforcement center 26, network center 24 signals RTU 18 of tower 16 (and all the towers in the network) to present a message to transceiver 40, FIG. 2. This message is processed by controller 44 which then activates transponder 42 accordingly.
When a vehicle is stolen, it is possible to disable a prior art VLU by injecting a high (e.g., 200 volt) input voltage into the VLU. When subjected to such an input voltage, the power supply unit, the transceiver, the transponder, and/or the microcontroller (or individual components thereof) can be damaged rendering the VLU inoperable.
But not in accordance with the subject invention due to the addition of protection circuit 52 configured to clamp the input voltage to VLU 10 at a predetermined maximum.
As shown in the example of FIG. 3, the protection circuit is integral with power supply circuit 50 which includes filtering circuit 60 connected to input voltage 62 from the vehicle's battery. First stage voltage regulating circuit 62 regulates the voltage output from filtering circuit 60 and second stage voltage regulating circuit 64 receives the regulated voltage output from first stage voltage regulating circuit 62 and is configured to provide the appropriate voltage levels to transceiver 40, transponder 42, and microcontroller 44.
In accordance with one preferred embodiment, every component of filtering circuit 60, namely capacitors 70, 72, and 74 and inductor 76 are selected to be able to withstand, without damage, an input voltage level much greater than the nominal 12 volt input voltage at 62. In one example, capacitor 70, 72, and 74 and can withstand 200 volts at input 62. The same is true with respect to the components of first stage regulating circuit 62. For example, capacitor 78 thereof can withstand a voltage of 200 volt. Moreover, first stage regulating circuit 62 includes voltage limiting diode 80 which clamps an input voltage as high as 200 volts as filtered by filtering circuit 60 to 12 volts. Thereafter, first stage voltage regulating circuit presents a 9 volt signal to second stage voltage regulating circuit 64 as is known in the art. Thus, other specific components of first stage voltage regulating circuit 62 and the specific components of second stage voltage regulating circuit 64 are not discussed further here.
In any embodiment, if, before law enforcement vehicle 20, FIG. 1 equipped with VTU 22 can locate stolen vehicle 14, a thief attempts to disable VLU 10 of stolen vehicle 14 by injecting a high voltage into VLU 10, protection circuit 52, FIG. 2 clamps the injected voltage at a nominal value allowing the proper operation of transceiver 40, transponder 42, and microcontroller 44. Before the high voltage level is clamped, any circuit components subject to the injected high voltage level are selected such that they can withstand the higher voltage level. In this way, VLU 10 operates correctly even if a thief attempts to disable it.
Specific features of the invention are shown in some drawings and not in others, but this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the following claims.
In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended.

## Claims

1. A vehicle locating unit comprising:
a receiver for receiving a signal from a network of communication sources;
a transponder activated when a communication source sends a message to the receiver;
a power supply regulating circuit for regulating a nominal vehicle input voltage and powering said receiver and said transponder; and
a protection circuit responsive to an injected input voltage at least an order of magnitude higher than the vehicle input voltage and configured to clamp the injected input voltage at a predetermined maximum voltage the same as or approximately the same as the vehicle input voltage, the protection circuit comprising:
a filtering circuit with at least one voltage protection device having a breakdown voltage at least as high as the injected input voltage, and
a voltage regulating circuit including at least one voltage protection device having a breakdown voltage at least as high as the injected input voltage.

2. The vehicle locating unit of claim 1 in which every component of the protection circuit is selected to withstand an injected input voltage greater than said nominal input voltage.

3. The vehicle locating unit of claim 1 in which the protection circuit includes a voltage limiting diode which clamps the injected input voltage at the predetermined maximum voltage.

4. The vehicle locating unit of claim 1 in which the protection circuit is integrated with the power supply regulating circuit.

5. The vehicle locating unit of claim 1 in which the power supply circuit further includes a second stage voltage regulating circuit connected to the first stage voltage regulating circuit and configured to provide the appropriate voltage levels to the receiver and transponder.