Radar warning receiver with position and velocity sensitive functions

RADAR WARNING RECEIVER WITH POSITION AND VELOCITY

SENSITIVE FUNCTIONS

0003Cross-Reference to Related Applications

0004This application is a United States continuation-in-part of U.S.

0005Provisional Patent Application serial no. 60/139,097, filed June 14, 1999, and

0006a United States continuation-in-part of U.S. Provisional Patent Application

0007serial no. 60/145,394, filed July 23, 1999, both of which are hereby

0008incorporated herein in their entirety.

0009Field of the Invention

0010The present invention relates to radar warning receivers.

0011Background of the Invention

0012Radar detectors warn drivers of the use of police radar, and the

0013potential for traffic citations if the driver exceeds the speed limit. The FCC has

0014allocated several regions of the electromagnetic spectrum for police radar use.

0015The bands used by police radar are generally know as the X, K and Ka bands. Each relates to a different part of the spectrum. The X and K bands are

0016relatively narrow frequency ranges, whereas the Ka band is a relatively wide

0017range of frequencies. By the early 1990's, police radar evolved to the point

0018that it could operate almost anywhere in the 1600-megahertz wide Ka band.

0019During that time radar detectors kept pace with models that included descriptive names like "Ultra Wide" and "Super Wide." More recently, police

0020have begun to use laser (optical) systems for detecting speed. This technology

0021was termed LIDAR for "Light Detection and Ranging."

0022Radar detectors typically comprise a microwave receiver and detection circuitry that is typically realized with a microprocessor or digital

0023signal processor (DSP). Microwave receivers are generally capable of

0024detecting microwave components in the X, K, and very broad Ka band. In

0025various solutions, either a microprocessor or DSP is used to make decisions

0026about the signal content from the microwave receiver. Systems including a

0027digital signal processor have been shown to provide superior performance over

0028solutions based on conventional microprocessors due to the DSP's ability to

0029find and distinguish signals that are buried in noise. Various methods of

0030applying DSP's were disclosed in U.S. Patent Nos. 4,954,828, 5,079,553,

00315,049,885, and 5,134,406, each of which is hereby incorporated by reference

0032herein. Police use of laser has also been countered with laser detectors,

0033such as described in U.S. Patent Nos. 5,206,500, 5,347,120 and 5,365,055,

0034each of which is incorporated herein by reference. Products are now available

0035that combined laser detection into a single product with a microwave receiver, to provide comprehensive protection.

0036The DSP or microprocessor in a modern radar detector is

0037programmable. Accordingly, they can be instructed to manage all of the user

0038interface features such as input switches, lights, sounds, as well as generate

0039control and timing signals for the microwave receiver and/or laser detector.

0040Early in the evolution of the radar detector, consumers sought products that

0041offered a better way to manage the audible volume and duration of warning

0042signals. Good examples of these solutions are found in U.S. Patent Nos.

00434,631,542, 5,164,729, 5,250,951, and 5,300,932, each of which is hereby

0044incorporated by reference, which provide methods for conditioning the response generated by the radar detector.

0045Methods for conditioning detector response are gaining

0046importance, because there is an increasing number of signals present in the X,

0047K, and Ka bands from products that are completely unrelated to police radar.

0048These products share the same regions of the spectrum and are also licensed by

0049the FCC. The growing number of such signals is rapidly undermining the

0050credibility of radar detector performance. Radar detectors cannot tell the difference between emissions from many of these devices and true police radar

0051systems. As a result, radar detectors are increasingly generating false alarms, effectively "crying wolf, reducing the significance of warnings from radar

0052detectors.

0053One of the earliest and most prevalent unrelated Microwave

0054sources is the automatic door system used in many commercial buildings such

0055as supermarkets, malls, restaurants and shopping centers. The majority of

0056these operate in the X-Band and produce signals virtually indistinguishable

0057from conventional X-Band Police Radar. Other than the fact that door opening

0058systems are vertically polarized, vs circular polarization for police radar, there

0059is no distinction between the two that could be analyzed and used by a receiver

0060design.

0061Until recently, virtually all of the door opening systems were

0062designed to operate in the X-Band. As a result, radar detectors generally

0063announced X-Band alerts far more often than K-Band. As these X-Band

0064'polluters' grew in numbers, ultimately 99% of X-Band alerts were from

0065irrelevant sources. X-Band alerts became meaningless. The only benefit that

0066these sources offered the user was some assurance that the detector was

0067actually capable of detecting radar. It also gave the user some intuition into

0068the product's detection range. To minimize the annoyance to users, most radar

0069detector manufacturers added a filter-like behavior that was biased against X- Band sources. Many also added "Band priority" that was biased against X and

0070in favor of bands that were less likely to contain irrelevant sources such as K,

0071Ka, and Laser. If signals in both X and K Bands were detected, band

0072prioritization would announce K, since it was more likely be a threat to the

0073driver. In the last few years, K-Band door opening systems have also grown in

0074number. This has reduced the significance of the K-Band warning and further

0075undercut the overall benefit to the user of a radar detector.

0076Another unrelated microwave signal is generated by traffic

0077management systems such as the ARTIMIS manufactured by TRW, used in

0078Cincinnati, Ohio. ARTIMIS Stands for "Advanced Regional Traffic

0079Interactive Management and Information System", and reports traffic flow

0080information back to a central control center. Traffic congestion and other

0081factors are analyzed by the control center. Control center employees use this

0082information to formulate routing suggestions and other emergency

0083information, which they transmit to a large distribution of overhead and

0084roadside signs. In order to collect information on vehicle traffic, a roadside

0085ARTIMIS station transmits an X-Band signal toward cars as they drive by.

0086The ARTIMIS source, unlike the X-Band door opener systems, is

0087distinguishable from police radar as it is not transmitted at a single fixed

0088frequency. As a result, it is possible to differentiate police radar signals from

0089sources such as ARTIMIS, and ignore ARTIMIS sources in newer detectors. Older detectors, however, do not incorporate this feature and could be obsolete

0090in areas where ARTIMIS is in use.

0091Unrelated Microwave signals are also transmitted by a system

0092called the RASHID VRSS. Rashid is an acronym for Radar Safety Brake

0093Collision Warning System. This electronic device warns heavy trucks and

0094ambulances of hazards in their path. A small number of these RASHID VRSS units have been deployed. They are categorized as a member of the 'non-

0095stationary' set of unrelated sources. As in the ARTIMIS example, detection of

0096RASHID can be prevented.

0097Perhaps the biggest source of non-stationary unrelated sources

0098is from other radar detectors. These are sometimes referred to as "polluting

0099radar detectors," and present a serious threat to some detector products. An

0100early example of this occurred in the mid 1980's when radar detectors using

0101superhomodyne circuitry became popular. Such detectors leak energy in the

0102X-Band and K-bands and appeared as police radar to other detectors. A

0103solution to this problem is described in U.S. Patent No. 4,581 ,769, which is

0104hereby incorporated by reference in its entirety. A similar problem occurred in

0105the early 1990's when the Ka band was widened. An unexpected result was

0106that the wider Ka band then also detected harmonics of signals generated by local oscillators within many existing radar detectors. U.S. Patent No. 5,305,007, which is hereby incorporated by reference in its entirety, describes

0107a method for ignoring these polluting detectors.

0108At this time, there are very few signal sources that can cause

0109false laser detections in comparison to the substantial list of false microwave

0110signals just described. However there are certain types of equipment that can cause the amplifiers and detection circuitry used in a laser detector to generate

0111a "false" detect. In particular, certain locations near airports have been

0112demonstrated to cause such problems for various laser detector products. As a

0113result, selected airport environments are examples of stationary signals that

0114produce false laser detections.

0115As can be appreciated from the foregoing example, as sources

0116of unrelated signals continue to propagate, radar detectors must continually

0117increase in sophistication to filter unrelated sources and accurately identify

0118police radar. Each of these changes and enhancements has the potential effect

0119of obsoleting existing detectors that do not include appropriate

0120countermeasures. Furthermore, some sources, particularly stationary door

0121opener sources, at this time cannot be filtered economically, and thus threaten

0122the usefulness of even the most sophisticated modern radar detector.

0123During the 1980's, the functionality of radar detectors

0124expanded into other classes of driver notification. A system was developed

0125that required a special transmitter be placed on emergency vehicles, trains, and other driving hazards. The term 'emergency radar' was coined, and a variety

0126of products were introduced that could detect these transmitters. One such

0127solution was disclosed in U.S. Patent No. 5,559,508, which is hereby

0128incorporated by reference herein in its entirety. Another system was later introduced offering a larger class of 'hazard categories' called the SWS

0129system. Both emergency radar and SWS involve the transmission of

0130microwave signals in the 'K' band. Such signals are considered to be a part of

0131the group of signal types that are intended to be detected by radar detectors.

0132A drawback of these warning systems is that stationary

0133transmitters of these signals send the same message to drivers constantly, and

0134become a nuisance during daily commute. This is beneficial to 'new' drivers

0135receiving the message for the first time. However these messages become an

0136annoyance to drivers who follow the same path to work everyday.

0137Thus, radar detector manufacturers are continually confronted

0138with new problems to solve, due to the variety of different types of unrelated

0139sources and their sheer numbers. The rate at which new or upgraded radar

0140detector models are introduced continues to increase as manufacturers try to

0141evolve their products to manage the growing number of unrelated sources.

0142Meanwhile, the market for radar detectors is shrinking because consumers are

0143no longer interested in buying products that so quickly become obsolete. Summary of the Invention

0144The present invention overcomes these difficulties by providing

0145a method of operating a radar detector that aids in the management of

0146unrelated sources, and permitting the detector to dynamically improve its

0147handling of unrelated sources. As noted above, many non-stationary sources

0148can be identified and ignored using existing technology. However, many

0149stationary sources cannot, as yet be effectively filtered economically with

0150existing technology. Accordingly, the invention provides a radar detector that includes technology for determining the location of the detector, and

0151comparing this location to the locations of known stationary sources, to

0152improve the handling of such detections.

0153In one embodiment, a radar detector may ignore detections

0154received in an area known to contain a stationary source. In the specific

0155embodiment described below, substantially more sophisticated processing is

0156performed to determine whether and what actions to take in response to a

0157detection.

0158The Global Positioning Satellite System (GPS) offers an

0159electronic method for establishing current physical coordinates very

0160accurately. In the detailed embodiment described below, a radar detector

0161utilizes a GPS system to determine its current position. The detector also

0162maintain a list of the coordinates of the known stationary source "offenders" in nonvolatile memory. Each time a microwave or laser source is detected, it

0163will compare its current coordinates to this list. Notification of the driver will

0164take on a variety of forms depending on the setup configuration.

0165By adding GPS conditioning capabilities to a radar detector, the

0166combination becomes a new product category that is capable of rejecting

0167signals from any given location no matter what the nature of the

0168microwave/laser signals might be from that location. This will have a dramatic effect on the usable life of the product and subsequent value to its owner.

0169The above and other objects and advantages of the present

0170invention shall be made apparent from the accompanying drawings and the

0171description thereof. Brief Description of the Drawing

0172The accompanying drawings, which are incorporated in and

0173constitute a part of this specification, illustrate embodiments of the invention

0174and, together with a general description of the invention given above, and the

0175detailed description of the embodiments given below, serve to explain the

0176principles of the invention.

0177Fig. 1 is an illustration of a vehicle receiving radar signals from

0178police radar and from a number of unrelated sources, and further receiving

0179global positioning signals from a global positioning satellite; Fig. 2 is an electrical block diagram of a radar detection circuit in accordance with principles of the present invention;

0180Fig. 3 is a illustration of a database structure used by the radar

0181detection circuit of Fig. 2, for storing information radar signals received or

0182receivable from unrelated sources at a number of locations, as identified by cell coordinates;

0183Fig. 4 is an illustration of a database structure used for storing

0184historic information on the locations of a vehicle carrying the radar detection

0185circuit of Fig. 2, as identified by cell coordinates;

0186Fig. 5 is an illustration of a database structure used for storing

0187flags identifying various conditions at a number of locations, as identified by

0188cell coordinates;

0189Fig. 6A is a flow chart of the operations of the CPU of the radar

0190detector of Fig. 2, carrying out principles of the present invention; Fig. 6B is a flow chart of operations of the CPU of Fig. 2 in

0191processing GPS information when GPS signals are being received;

0192Fig. 6C is a flow chart of operations of the CPU of Fig. 2 in

0193updating stored information when a radar signal is being received;

0194Fig. 6D is a flow chart of operations of the CPU of Fig. 2 in

0195updating stored information when a radar signal is not being received; Fig. 6E is a flow chart of operations of the CPU of Fig.2 in

0196responding to keypad activity to change operative mode of the GPS enabled radar detector; and

0197Fig. 6F is a flow chart of operations of the CPU of Fig. 2 in

0198generating audible and visible responses based upon operating modes of the

0199radar detector and the presence or absence of radar signals and stored

0200information.

0201Detailed Description of Specific Embodiments

0202To provide background for the present invention, a summary of

0203GPS (Global Positioning System) technology will now be provided. GPS is a

0204mature technology that provides a method for a GPS receiver to determine its

0205relative location and velocity at any time. The (GPS) system is a worldwide

0206constellation of 24 satellites and their ground stations. GPS receivers on earth

0207use 'line of sight' information from these satellites as reference points to

0208calculate positions accurate to a matter of meters. Advanced forms of GPS

0209actually enable measurements to within a centimeter. The Global Positioning

0210System consists of three segments: a space segment of 24 orbiting satellites, a

0211control segment that includes a control center and access to overseas command

0212stations, and a user segment, consisting of GPS receivers and associated

0213equipment. Over time GPS receivers have been miniaturized to just a few

0214integrated circuits and have become very economical. An unfortunate side effect of the GPS system is that it can be

0215used by enemy forces, as GPS signals can be picked up by any receiver including both domestic and foreign. When the United States Department of

0216Defense devised the GPS system they incorporated a feature that prevents high

0217precision measurements unless the receiver is equipped with special military

0218'keys.' This is accomplished with the intentional introduction of "noise" into

0219the satellite's clock data which adds noise (or inaccuracy) into position

0220calculations. The DOD sometimes also sends slightly erroneous orbital data to

0221the satellites, which is transmitted back to receivers on the ground. This

0222intentional degradation is referred to as "Selective Availability" or "SA" error.

0223Military receivers use a decryption key to remove the SA errors. As a result of

0224the SA error, there are two classes of GPS service, "Standard Positioning

0225Service (SPS) and "Precise Positioning System" (PPS.). These classes are

0226realized by having GPS satellites transmit two different signals: the Precision

0227or P-code and the Coarse Acquisition or C/A-code. The P-code is designed

0228for authorized military users and provides PPS service. To ensure that

0229unauthorized users do not acquire the P-code, the DOD can engage an

0230encryption segment on the P-code called anti-spoofmg (AS). The C/A-code is

0231designed for use by nonmilitary users and provides SPS service. The C/A-

0232code is less accurate and easier to jam than the P-code. It is also easier to

0233acquire, so military receivers first track the C/A-code and then transfer to the P-code. Selective availability is achieved by degrading the accuracy of the

0234C/A-code.

0235The precision of SPS is stated as providing 100-meter

0236horizontal and 156 meter vertical accuracy "95% of the time." PPS is only

0237available for the U.S. and allied military, certain U.S. Government agencies,

0238and selected civil users specifically approved by the U.S. Government. PPS

0239provides 22 meters horizontal and 22.7 meters vertical accuracy 95% of the

0240time.

0241Other than intentional errors inserted by the DOD, there are a

0242variety of other error sources that vary with terrain and other factors. GPS

0243satellite signals are blocked by most materials. GPS signals will not pass

0244through buildings, metal, mountains, or trees. Leaves and jungle canopy can

0245attenuate GPS signals so that they become unusable. In locations where at

0246least four satellite signals with good geometry cannot be tracked with

0247sufficient accuracy, GPS is unusable.

0248The "Differential GPS" system was developed in order to

0249compensate for the inaccuracy of GPS readings. A high-performance GPS

0250receiver (known as a reference station or beacon) is placed at a specific

0251location; the information it receives is then compared to the receiver's location

0252and corrects the SA satellite signal errors. The error data is then formatted

0253into a correction message and transmitted to GPS users on a specific frequency (300 kHz). A true or arbitrary set of coordinates are assigned to the position

0254occupied by a reference GPS receiver. The difference between these and the

0255coordinates received via GPS at the reference is a very close approximation to

0256the SA error at nearby sites. This error is nearly identical to the error

0257calculated by any nearby GPS receiver. The reference site is sometimes

0258referred to as a 'beacon,' as it constantly transmits these difference

0259coordinates. A DPGS receiver is designed to receive both the GPS

0260information and the beacon information. It generates a far more accurate

0261estimate of its coordinates by applying the difference information to the GPS

0262coordinates. The drawback to this is that the remote and reference receivers

0263may not be using the same set of satellites in their computations. If this is the

0264case, and the remote receiver incorporates the corrections, it may be

0265accounting for satellite errors that are not included in its own measurement

0266data. These corrections can make the differential solution worse than the

0267uncorrected GPS position. To prevent this error, an improved form of differential GPS involves the derivation of the corrections to the actual

0268measurements made at the reference receiver to each satellite. By receiving all

0269of the corrections independently, the remote receiver can pick and choose

0270which are appropriate to its own observations. This method of DGPS is most

0271widely used. Typically, the DGPS correction signal loses approximately 1 m

0272of accuracy for every 150 km of distance from the reference station. The availability of Beacons for DGPS systems elevate the very

0273threat that the SA error was intended to reduce. In the presence of such

0274networks, potentially hostile weapons systems using DGPS could be

0275developed relatively rapidly. For this reason and others, the SA error has

0276diminished in military significance. The White House has Directed that the

0277S/A error be "Set to Zero" by the year 2006.

0278In the United States, the US Coast Guard (USCG) and Army Corps of Engineers (ACE) have constructed a network of Beacon stations that

0279service the majority of the eastern United States, the entire length of both

0280coastlines, and the Great Lakes. Further plans exist to increase the density of

0281this network to provide dual redundant coverage throughout the continental

0282US by the end of the year 2000 for a variety of applications including

0283intelligent transportation system, infrastructure management, and public

0284safety.

0285The Canadian Coast Guard (CCG) provides coverage in

0286Canada for the St. Lawrence River, throughout the Great Lakes, and both

0287coastlines. In total, there are over 160 stations operational worldwide with

0288over 140 sites proposed to come online within the next two years. Coverage currently exists in many other regions of the world including Europe, Asia,

0289Australia, Africa, and South America. The beacons perform the differential calculation and broadcasts this information by modulating the data onto a 300 kHz signal transmitted by

0290the established network of Radiobeacons. The advantages of using the Beacon

0291DGPS network include: (1) Free access to differential correction information;

0292(2) Long range signal which penetrates into valleys, and travels around

0293obstacles; (3) High quality differential corrections which are continuously

0294monitored for integrity; and (4) Inexpensive user equipment.

0295The range of the 300 kHz signal is dependent upon a number of

0296factors which include transmission power and conductivity of the surface over

0297which the transmission is propagating. The Beacons within the global network broadcast at varying power. Typical broadcasting ranges for

0298radiobeacons vary from as little as 35 nautical miles to as much as 300

0299nautical miles. Signals broadcast by DGPS radiobeacons are integrity

0300monitored by remote stations for quality of beacon transmission, differential

0301corrections, and GPS positional information. In addition, government

0302agencies concerned with public safety have made it their mandate to ensure

0303that beacon DGPS services are available 24 hours a day, 365 days a year.

0304Performance requirements for marine applications dictate that an availability

0305of 99% or greater is required if a particular system is to be used as a sole means of navigation. The US Coast Guard and Army Corps of Engineers Beacon Network, for example, offer this high level of availability free of

0306charge to all civilian users.

0307There are other navigation systems in place, in addition to GPS,

0308that merit review. LORAN-C is a ground-based radio navigation system. It

0309operates on a frequency band of 90 kHz to 1 10 kHz (LF). It has an

0310approximate range of hundreds to thousands of miles, and an accuracy of 0.25

0311nautical miles repeatable to 18 - 90 meters, with 95% confidence. Loran-C is

0312a pulsed hyperbolic system that provides 0.25 nm predictable accuracy, 18 - 90

0313m repeatable accuracy, 95% confidence and 99.7% availability. Loran-C

0314provides coverage for the continental U.S. and its coastal waters, the Great

0315Lakes, and most of Alaska. Many other countries are also involved in the

0316providing of Loran-C (or Loran-like) services, or are in negotiations with their

0317neighbors to expand coverage. These countries include India, Norway, France.

0318Ireland, Germany, Spain, Italy, Russia, China, Japan, the Philippines and

0319others.

0320Omega is a low frequency band system with accuracy of 2 to 4

0321nautical miles with 95% confidence level. Developed by the United States, it

0322is operated in conjunction with six other nations. OMEGA is a very low

0323frequency, phase comparison, worldwide radionavigation system

0324Tacan operates in the U.S. in a frequency band of 960 MHz -

03251215 MHz (UHF). It has a range of approximately 200 miles at high altitudes. TACAN is primarily used by U.S. and other military aircraft. TACAN radio

0326stations are often co-located with civilian VOR systems allowing military

0327aircraft to operate in civil airspace. The system provides the pilot with relative

0328bearing and distance to the radio beacon.

0329VOR operates in a frequency band of 108.0 MHz - 117.95 MHz

0330(VHF). It has an approximate range of 250 miles, but accuracy as poor as 20

0331miles. VOR is a beacon-based navigation system operated in the U.S. by the

0332Federal Aviation Administration (FAA) for civil aircraft navigation. When

0333used by itself, the system allows users to determine their azimuth from the

0334VOR station without using any directional equipment. VOR stations are radio

0335beacons that transmit two signals. The first, called the reference signal, is

0336transmitted with constant phase all around the transmitter. The second signal

0337is phase shifted from the first depending on the compass direction of the user

0338from the station. A simple, inexpensive receiver in the aircraft is used to

0339determine the received phase difference of the two signals, and from that

0340information the direction of the aircraft from the transmitter. By using two

0341VOR stations, a specific location may be determined.

0342Of all the navigation systems mentioned, GPS offers better

0343service, more accuracy, and more serviceable regions than any other approach.

0344There are various classes of GPS service that improve accuracy at higher costs.

0345These include the following categories: (1) Low-cost, single receiver SPS projects (100 meter accuracy); (2) Medium-cost, differential SPS code

0346Positioning (1-10 meter accuracy); (3) High-cost, single receiver PPS projects (20 meter accuracy); (4) High-cost, differential carrier phase surveys ( 1 mm to

03471 cm accuracy); and (5) High-cost, Real-Time-Kinematic (1 cm) with real time

0348accuracy indications.

0349Referring now to Fig. 1, a vehicle 10 is illustrated in operation

0350on a roadway, under exposure to radio frequency signals from a variety of

0351sources. These include the GPS satellite system, LORAN or OMEGA radio

0352towers, non-police sources of interference such as restaurant 16, and police

0353radar signals from a radar gun 18. In accordance with principles of the present invention, vehicle 10 is equipped with a radar detector able to identify the

0354present coordinates and/or velocity of the vehicle, e.g. using an associated

0355GPS receiver or alternatively a receiver of land-based signals such as LORAN.

0356The radar detector is able to use this information to enhance its decision-

0357making abilities.

0358Referring now to Fig. 2, the radar detector 20 in accordance

0359with principles of the present invention includes a fusion processor 22 for

0360controlling all functions of the unit. Fusion processor receives information on

0361radar signals from a conventional microwave receiver 24, coupled to processor

036222 via a digital signal processor (DSP) 26. Microwave receiver 24 and DSP

036326 may utilize any of the techniques described above and in the above- referenced patents, for rejecting noise and increasing discrimination between

0364actual and spurious police radar signals. Further, receiver 24 and DSP 26 may

0365be controlled by an optional second CPU 25, which can enable additional

0366signal evaluation beyond that which is possible using a DSP.

0367Processor 22 is further connected to a laser detector 28 for

0368detecting police LIDAR signals. Processor 22 is further connected to a GPS

0369receiver 32 and a separate differential GPS (DGPS) receiver 30, such that

0370differential GPS methodologies may be used where beacon signals are

0371available. Since the radar detector application described in this patent is not a

0372candidate for military class service, it is not able to access the more accurate

0373PPS. However it is considered a "civil user" and can use the SPS without

0374restriction.

0375Processor 22 executes a stored program, found in an electrically

0376erasable programmable read only memory (EEPROM) 34, flash memory, or

0377masked read only memory (ROM). The processor is programmed to manage

0378and report detected signals in various ways depending on its stored program. This programming includes functions for "detector response conditioning," as

0379elaborated below, e.g., with reference to Figs. 6 A through 6D.

0380The radar detector further incorporates a user input keypad or

0381switches 36. Operational commands are conveyed by the user to processor 22

0382via the keypad. Processor 22 is further connected to a display 38, which may comprise one or more light emitting diodes for indicating various status conditions, or in a more feature-rich device, may include an alphanumeric or

0383graphical display for providing detailed information to a user. A speaker 40 is

0384also provided to enable processor 22 to deliver audible feedback to a user

0385under various alert conditions, as is elaborated below.

0386Processor 22 may further include an interface 44, such as an

0387ODB II compliant interface, for connection to vehicle electronic systems 42

0388that are built into the vehicle 10. Modern vehicles are being equipped with

0389standardized information systems using the so-called OBD II standard

0390interface. This standard interface is described in an article entitled ODB II

0391Diagnostics, by Larry Carley, from Import Car, January 1997, which is hereby

0392incorporated herein by reference. Processor 22, using the OBD II standard

0393interface 44, can obtain vehicle speed and other vehicle status information

0394directly from the vehicle, and then may use this information appropriately as

0395described in more detail below.

0396Processor 22 is further coupled to a Universal Serial Bus (USB)

0397interface 46 that provides a means for uploading and downloading information

0398to and from processor 22. Specifically, USB interface 46 may be used to

0399automate the assimilation of coordinate information into data structures in EEPROM 34, as described below with reference to Figs. 3 through 5. USB

0400interface 46 may also be used to interface the detector to a separate host computer or product application containing a larger storage capacity than

0401available from internal memory. Remote storage devices may include any

0402form of dynamically allocatable storage device (DASD) such as a hard disk drive, removable or fixed magnetic, optical or magneto-optical disk drive, or

0403removable or fixed memory card, or any device including a dynamic directory

0404structure or table of contents included in the storage format to permit dynamic

0405storage allocation. The host computer or other connected device need not be

0406visible to the driver and may be in any convenient location, such as under the

0407vehicle dash.

0408Coordinate information can be stored, e.g., on a hard drive

0409organized with an indexed database structure to facilitate rapid retrieval, and

0410the hard drive may include a special purpose processor to facilitate rapid

0411retrieval of this information.

0412Where a general purpose host computer is connected via the

0413USB interface, it will likely be based on a higher scale CPU chip and thus be

0414able to efficiently carry out complex coordinate comparison tasks such as are

0415described below, and such tasks may be delegated to the host CPU rather than

0416carried out in fusion processor 22. The host CPU can also anticipate the need

0417for information about particular coordinates based upon vehicle movements,

0418and respond by retrieving records within proximity of the current location for

0419ready delivery to fusion processor 22. The host computer can also provide navigational functions to the driver, potentially using stored signal information

0420and flag bits to provide the user with location-specific information about

0421driving hazards and potential police stakeout locations.

0422Signal information may also be downloaded from other hosts,

0423for example, a connection may be established directly via the USB interface to

0424an Internet site carrying signal information, as is now done in a text form at the

0425Internet site speedtrap.com. An indirect Internet connection may also be

0426established via a host computer. Furthermore, connections may be established

0427between two receivers, e.g. a trained receiver having extensive signal

0428information, and a receiver having less extensive information, to transfer

0429signal information between the receivers so that either or both has a more

0430complete set of signal information.

0431Generally speaking, processor 22 compares the radar detector's

0432immediate coordinates with a stored list of the coordinates of unwanted

0433stationary sources. If the radar detector receives a microwave/laser signal

0434within a certain distance of one of these pre-designated sources, processor 22

0435applies additional constraints to the detection criterion before alerting the user.

0436Since stationary radar sources make up the bulk of the unwanted sources, there is a significant benefit resulting from these functions. Further details on these

0437operations are provided below with reference to Figs. 6A through 6D. Fig. 3 illustrates data structures 50 stored in EEPROM 34 and used for managing information utilized in accordance with principles of the

0438present invention. As seen in Fig. 3, these data structures include a plurality of

0439main entries 52, each including a field 54 for a coordinate, a field 56 for

0440identifying the date and time data was collected, and three fields 58, 60 and 62

0441providing information on the source.

0442Field 54 provides the coordinate of a "cell" of space. As will be

0443elaborated below, coordinates provided by GPS receiver 32 are reduced in

0444resolution to arrive at a "cell" coordinate, which indicates that the current

0445location of the receiver is within a relatively large (e.g., 1/8 or 1/4 mile square) block of space on the Earth's surface. This approach reduces the storage

0446requirements for information stored by the radar detector to a manageable

0447level. The sizes of the cells can be variably adjusted based upon the available

0448memory and the desired precision. In the present example, 128 bits are

0449allocated to storing cell coordinates, so the cell coordinates can only have as

0450much precision as can be provided in 128 bits, a cell, e.g., by discarding the

0451least significant bits of the coordinates. In other applications, different bit

0452sizes and resolutions could be utilized. It will also be noted that the storage

0453requirements can be reduced by designing the receiver for operation only in a

0454specified part of the Earth, e.g., only in Europe, Japan or North America. By

0455so doing, part of the coordinates for a cell will not need to be stored because they will be the same for all stored cells. In such an embodiment, whenever

0456the coordinates provided by the GPS receiver fall outside of the pre- established region, the receiver will either disable all storage of information (if

0457approved via operational input from the user), or establish a new region of

0458interest and discard all data from previously identified regions. Alternatively,

0459the operator may set the device in either a "precision" (high coordinate

0460resolution) or "wide area" (low coordinate resolution) mode, based upon the

0461driving habits of the driver. In "wide area" mode, the reduced resolution used

0462for each cell coordinate permits a greater number of coordinates to be stored,

0463albeit with reduced precision as to each coordinate. Rural drivers and others

0464that often follow common paths, would be best suited to "precision" mode,

0465whereas urban drivers would be better suited to "wide area" mode. As a further alternative, the detector may automatically select a mode based upon

0466the memory consumption or the time lapse before the memory of the detector

0467becomes full; if the memory fills rapidly, the unit would automatically switch

0468to a "wide area" mode using low precision coordinates, whereas if the memory

0469never fills or fills only slowly, the unit will remain in its "precision" mode.

0470The date and time information in field 56 is useful when

0471selecting least recently used (oldest) entries in storage for replacement, as is

0472described further below. Fields 58, 60 and 62 store source incidence counters, one for

0473each of a plurality of frequency blocks. Field 58 stores counter(s) for block(s)

0474in the X band. Field 60 stores counter(s) for block(s) in the K band. Field 62

0475stores counter(s) for block(s) in the Ka band. The number of blocks in each

0476band can vary in different embodiments of the present invention, and is a

0477function of the signal frequency content details provided by the detector 24

0478and DSP 26. As one example, the X, K and Ka bands are divided into a total

0479of 32 frequency blocks. Each block is provided a 4-bit counter in fields 58, 60

0480and 62. The counters have a minimum value of 0 and a maximum value of 15.

0481and are a measure of the number of times a signal in the associated frequency

0482block has been detected at that location. As will be described below in greater

0483detail, the "source incidence" counters are used in identifying geographic

0484locations that appear to have spurious sources of police radar signals, due to repeated detection of such signals without confirmation of police activity.

0485In the data structures shown in Fig. 3, to save space, main

0486entries 52 are interleaved with a greater number of differential entries 64, each

0487of which stores information for a cell. A first field in a differential entry 64 is

0488an index pointer 66 to a main entry 52, e.g. an index to a storage location at

0489which the main entry is stored. A second field is a differential field 68 that

0490identifies the difference between the coordinate of the differential entry 64 and

0491the coordinate stored in the main entry 52. The index and differential can be stored in substantially fewer than 128 bits, so that a differential entry 64 is substantially smaller than a main entry, thus saving storage space. Differential entries further include a date and time field 56 and fields 58, 60 and 62 for

0492storing counters for X, K or Ka frequencies, as described above.

0493Fig. 4 illustrates data structures 70 used to store vehicle motion

0494history records or trip records in EEPROM 34. These data structures include

0495main entries 72 which include field 74 storing a 128 bit cell coordinate,

0496followed by a speed field 76 which can be, for example, 7 bits in length.

0497Differential entries 78 associated with each main entry include a differential

0498coordinate field 80 indicating the difference in the cell coordinate from the associated main entry 72, and a speed field 76 indicating a speed recorded at

0499the cell. Because motion history records or trip records are stored sequentially

0500during motion of the detector, differential entries 78 are stored after and

0501adjacent to the associated main entry 72. Accordingly, differential entries 78

0502do not require an index field to associate the differential entry 78 with a main

0503entry 72, because the association is implied from the location of the

0504differential entry 78 in memory after its associated main entry 72.

0505History entries may be used for a number of purposes. For

0506example, in the following description, history entries are accessed as part of

0507defining an "everyday route" taken by the detector at the operator's

0508identification. History entries may also be used for driver monitoring; they may be downloaded to a host PC via USB interface 46, and evaluated to

0509determine whether the vehicle has taken abrupt turns, show excessive speed,

0510or entered undesired locations, all of which may be useful in monitoring the activity, e.g., of teenage drivers. History entries may also be uploaded to PC

0511to provide evidence of the driving history of the vehicle before and at the time

0512of a police citation for speeding. If a driver has been unfairly cited for

0513speeding, history records from the detector can provide compelling evidence to court that the citation is in error. For the purpose of enabling these uses,

0514history entries stored by fusion processor 22 are encrypted when stored and

0515cannot be modified by fusion processor 22 or any PC software supplied for

0516viewing those entries.

0517Fig. 5 illustrates data structures 82 that can be used to store hazard information and other flag bits related to cells. These data structures

051882 include main entries 84 which include a full 128 bit cell coordinate in field

051988, followed by a date and time field 90 and flag bits 92 indicating the hazard

0520or condition associated with the identified location. The differential entries 86

0521include an index field 94 pointing to one of the main entries, a differential

0522coordinate field 96 indicating the difference in the cell coordinate from the

0523associated main entry 84, a date and time field 98, and a set of flag bits 92

0524indicating the hazard or condition associated with the identified location. The

0525flag bits may identify various hazard conditions. For example, in the specific embodiment described below, there is an "always warn" flag bit that indicates that police activity has previously been confirmed at the location, and

0526therefore the user should be warned of all apparent police radar signals at the

0527location. Further, there is a "location lockout" flag that indicates that

0528broadband sources of spurious police radar signals have been experienced at

0529the location, and therefore in the future warnings of police radar signals should

0530be suppressed at the location. Similarly, a "minimal visual lockout" flag

0531indicates that, due to the unwanted distraction of spurious police radar

0532warnings at a location, only a minimal visual warning should be made of

0533police radar signals identified at the location. The flag bits further include

0534"frequency lockout" bits, one for each frequency block identified by the radar

0535receiver. These bits identify frequencies at the location in which spurious

0536police radar signals have previously been encountered, so that in the future

0537apparent police radar signals at the same frequencies are ignored. The flag bits

0538may also include additional flags to warn of other conditions, such as that

0539there was construction at the identified location, or that some other cause for

0540traffic slowdowns were seen at the identified location, to aid in vehicle

0541navigation.

0542The information contained in the databases of Figs. 3 and 5

0543may be assimilated by the detector through operation, as is described below.

0544Alternatively, this information may be pre-installed in the detector, e.g. via an upload from a host PC via the USB port 46. There would be substantial benefits to pre-training a detector in this way for a particular geographic area.

0545By pre-training the detector, the driver would not have to enure the audible

0546alerts that would naturally occur before it is trained for each source of spurious

0547police radar signals. In a give area, the ideal training profile would not vary

0548much from one detector to the next, since all detectors should reject the same

0549sources in the same areas. As a result, there are few issues that would have to

0550be resolved in order to transfer training information from one radar detector.

0551The Internet provides a convenient means for storing and

0552accessing repositories of information. Web sites will be established and

0553devoted to this task. They will provide several convenient types of training

0554information. One will be a training file containing the coordinate information

0555from the online "Speed Trap Registry" at the internet site www.speedtrap.com.

0556This information would be usable to set "always warn" bits at the locales of

0557known speed traps. A second type of training information would be training

0558files submitted by individuals for use in particular areas, and the third type of

0559information would be aggregate training files created by integrating

0560individually-submitted information into single files organized by region.

0561Aggregate training files would be managed and updated by the web site

0562administrator. Training files would have low value if they could not be readily

0563used by other detectors. The transferability of training files from one detector

0564to another will depend on the differences in how real world signals are

0565perceived by their embedded processors. In large part, these differences are a

0566direct result of manufacturing and component variations. During the

0567manufacturing process, a detector goes through a set of calibration steps in

0568order to guarantee that the unit meets specifications for Spectral Band Coverage and Sensitivity. These calibration steps reduce the cost of designing

0569the product since lower cost, poorer tolerance components can be used on the

0570assumption that a final manufacturing calibration procedure will eventually

0571compensate for the lower tolerance. Once calibrated, an acceptable product

0572must also be able to perform over a predefined temperature range.

0573Component tolerance, manufacturing calibration, and operating

0574temperature are key factors that determine how the spectrum of microwave

0575signals are 'viewed' by the embedded Microprocessor or DSP. Radar products

0576convert the spectral band such as X-Band into an array of values that are

0577proportional to the signal energy in consecutive slots or bins of the spectrum.

0578In order for the product to be 'in tolerance' these slot positions must be

0579adjusted so they precisely cover the full range of X, K, and the Ka bands

0580The calibration procedure is only concerned with guaranteeing

0581that the slots provide adequate coverage of each band. It is less concerned as to whether any one of these slots falls on a precise physical frequency. Therefore

0582the first frequency block in one detector will not necessary be perceived at the

0583same frequency as the first slot in another detector.

0584If training data is to be shared between various detectors, it will

0585be necessary for supporting software to compensate for these variations. When

0586new pre-trained data is supplied, the detector will undergo an authentication

0587procedure in order to determine the relationships between the pre-train data

0588and its own receiver configuration. This will be based on comparing the

0589frequencies of newly encountered sources to those of the pre-train data at matching coordinates. By comparing the observed frequencies to those in the

0590training set, a "correction profile" will be constructed, that represents the

0591change between the pre-train data and the output of the local microwave

0592receiver. At the end of the authentication procedure, the entire pre-training file

0593will be incorporated into the active train data. During the authentication

0594procedure, the user will be exposed to unconditioned detector responses. This

0595authentication procedure will be substantially shorter than the training period

0596of a virgin detector. Once authentication is complete, the user will receive a

0597notification indicating that the product is switching from authentication over to

0598normal operation. If the training mode is engaged, the authenticated data will continue to be massaged by new driving encounters, as detailed below. Referring now to Fig. 6A, operations of the fusion processor 22

0599to carry out principles of the present invention can be described in greater

0600detail. Fusion processor 22 performs a main loop of steps during regular operation of GPS enabled radar detection. This main loop of steps is

0601illustrated in Fig. 6A and is detailed in Figs. 6B through 6F.

0602When fusion processor 22 is initialized, i.e., when power to the

0603GPS enabled radar detector is turned on, the device is initialized in step 100.

0604This initialization step includes performing diagnostic checks on the various

0605circuitry illustrated in Fig. 2 to insure its proper operation, as well as

0606initialization of the GPS receiver 32 to insure GPS signals can be received

0607accurately by fusion processor 22. In addition, various internal variables, such

0608as a variable for identifying a current position, are initialized. The initial values are chosen to insure proper operation; for example, the current position

0609variable is initialized to a value that will cause the first pass through the main

0610loop Fig. 6A to include processing of a current location in steps 1 10 and 1 12

0611in accordance with Figs. 6B-6E, as discussed below.

0612The first step in the main loop performed by fusion processor

061322, is step 102, in which radar detection circuitry 24 and 26 is accessed to

0614obtain information on police radar signals currently being received by the GPS

0615enabled radar detector. In a subsequent step 104, fusion processor 22

0616communicates with GPS receiver 32 to request a current location and a current vehicle speed from the GPS receiver 32. This information can then be utilized

0617in performing GPS related operations described in the following steps. As

0618noted above, vehicle speed may also be obtained from the vehicle itself via an

0619OBDII interface 44 if the vehicle in which the GPS enabled radar detector is

0620installed has a suitable OBD connector for delivering vehicle speed

0621information. It will be appreciated further that vehicle location information

0622might also be obtained via an OBDII connector from a GPS receiver that may

0623be built into the vehicle within which the GPS enabled radar detector is

0624installed. When the vehicle in which the GPS enabled radar detector is

0625installed has both vehicle speed and vehicle position information available via

0626an OBDII connector, the GPS receiver 32 may not be used at all, or may not

0627even be included in the GPS enabled radar detector, to facilitate cost reduction

0628for the GPS enabled radar detector.

0629Following steps 102 and 104 in which current police radar and

0630GPS related information is obtained, different actions are taken based upon

0631whether GPS information is available. Specifically, in step 106 it is

0632determined whether a GPS signal has been received. If a GPS signal is available, then all GPS enhanced functions of the radar detector may be

0633performed. If no GPS signal has been received, then the radar detector will

0634revert to processing police radar signals at a manner analogous to conventional

0635non-GPS enabled radar detectors. Assuming for the moment that a GPS signal is available in step

0636106, and therefore a current position for the vehicle is known, then in step 108 a sequence of steps is preformed to process the GPS signal, as is further

0637detailed below with reference to Fig. 6B, 6C and 6D. This processing can

0638include retrieval and/or updating of stored police radar information and the

0639signal information database illustrated in Fig. 3, the vehicle history database

0640illustrated in Fig. 4, and/or the flag database illustrated in Fig. 5.

0641After processing the GPS signal, in step 110 keypad activity on

0642keypad 36 is detected and processed to alter operating modes of the GPS

0643enabled radar detector, as described below in further detail with reference to

0644Fig. 6E. The operative modes controllable through the keypad include:

0645• a "warning suppression" mode in which warnings,

0646particularly audible warnings, produced by the GPS enabled

0647radar detector are suppressed so that they are not disturbing to

0648the operator of the vehicle.

0649• an "expert meter" mode in which detailed information

0650regarding received warning signals are displayed on display 38

0651of the GPS enabled radar detector, as described in U.S. Patent

06525,668,554, which is hereby incorporated by reference herein in its entirety. • a "data overwrite" mode in which the GPS enabled radar

0653detector saves, into the signal information database of Fig. 3,

0654data regarding any location not previously stored in the

0655database, even when this signal information database is full, by

06565 overwriting the oldest data in the signal information database

0657when necessary. When the "data overwrite" mode is disabled,

0658then the signal information database will not be overwritten

0659once it becomes full.

0660• a "frequency lockout" mode, in which police radar

066110 frequencies detected by the receiver are taken to be from non-

0662police sources, and appropriate flags are set in the flag database

0663illustrated in Fig. 5. The "frequency lockout" mode is engaged by the vehicle operator when non-police radar signals are being

0664received and the operator wishes to suppress future warning

066515 signals caused by the same sources at the same geographic

0666locations. As noted below, "frequency lockout" mode can only

0667be engaged while the GPS enabled radar detector is detecting

0668an apparent police radar signal and will be automatically

0669disengaged when this signal is no longer being received.

067020 • a "location lockout" mode, in which the flag database of Fig.

06715 is updated to suppress all audible warnings of radar signals at the current location of the vehicle. As is the case with the

0672"frequency lockout" mode, the "location lockout" mode will be

0673enabled by a vehicle operator when the vehicle is near to a

0674known source of spurious police radar signals of a broadband

06755 character. The "location lockout" mode can only be engaged

0676while the GPS enabled radar detector is detecting an apparent

0677police radar signal, and will be automatically disengaged

0678whenever a police radar signal is no longer being received from

0679the GPS enabled radar detector.

068010 • a "minimal visual lockout" mode, in which the flag database

0681of Fig. 5 is updated to suppress most or all visual warnings of

0682radar signals at the current location of the vehicle. The

0683"location lockout" mode will be enabled by a vehicle operator

0684when the vehicle is near to a known source of spurious police

068515 radar signals of a broadband character, and at that location does

0686not wish to be disturbed by even a visual radar signal warning.

0687The "location lockout" mode can only be engaged while the

0688GPS enabled radar detector is detecting an apparent police

0689radar signal, and will be automatically disengaged whenever a

069020 police radar signal is no longer being received from the GPS

0691enabled radar detector. • a "police confirmation" mode, in which flags in the flag

0692database of Fig. 5 will be set to insure a warning signal is always delivered for any police radar signal received at the

0693current vehicle location. The "police confirmation" mode will

06945 be activated by a vehicle operator upon sighting a police

0695stakeout.

0696• a "training" mode, in which the GPS enabled radar detector

0697will store signal information for all geographic locations that

0698the GPS enabled radar detector reaches or passes during

069910 operation. When "training" mode is disabled, the signal

0700incidence counters found in the signal information database of

0701Fig. 3, will not be modified by the GPS enabled radar detector

0702during its normal operation.

0703• a "route identification" mode in which the route currently

070415 traveled by the vehicle is memorized by the GPS enabled radar

0705detector to be subsequently referenced in performing radar

0706detection. Using "route identification" mode, a user may

0707establish one or more everyday routes traveled by the vehicle,

0708and cause the GPS enabled radar detector to continuously

070920 update its signal incidence information in the signal

0710information database of Fig. 3 whenever one of these routes are traversed. Routes are identified by an operator by entering the

0711"route identification" mode at the beginning a route, and then

0712exiting the "route identification" at the end of the route.

0713After selecting appropriate modes based upon keypad activity,

0714in step 112, an appropriate audible or visible response is produced by the GPS

0715enabled radar detector based upon it current operating mode and the presence

0716or absence of radar detector signal received in step 102. Details of this

0717operation are described below with reference to Fig. 6F. After step 112,

0718processing returns to step 102 to obtain a new radar detector signal output and

0719a new current location and speed and then perform additional analysis of that

0720data as described above.

0721As noted above, in some circumstances a GPS signal will not

0722be available during operation of the GPS enabled radar detector. In this case,

0723processing continues from step 106 to step 114 in which any non-GPS related

0724operational modes may be activated based upon the activity at keypad 35.

0725GPS enabled modes are unavailable so long as no GPS signal has been

0726obtained, so the processing in step 1 14 eliminates those modes which cannot be activated in the absence of a GPS signal. After step 1 14, processing

0727continues to step 112 in which an appropriate audible or visible response is

0728generated based upon the current operating mode and the radar detected signal

0729received in step 102. Referring now to Fig. 6B, the processing performed on a GPS signal in step 108 of Fig. 6A can be described in greater detail. As a first

0730step 120, GPS coordinates received from the GPS receiver 32 are modified by

0731reducing their accuracy. This process is known as "gridding" the coordinates

0732and involves truncating that part of the coordinate of greater accuracy than the

0733defined grid. As a consequence of this modification, the GPS coordinate is

0734mapped into a cell number; every location on the globe falls within a cell of

0735the grid, and has a particular cell number derived from the most significant

0736bits of the GPS coordinates measured within the cell. Cells may be relatively small, i.e., one-eighth of a mile square, or may be relatively large, i.e., one mile square.

0737After a current cell number is generated from GPS coordinates,

0738then actions are taken based upon whether the vehicle is transitioning from

0739one cell to another, and further based upon current operational modes of the

0740GPS enabled grid are detected. In the first of these steps 122, it is determined

0741whether the current cell obtained from the GPS receiver is the same a stored

0742prior cell obtained from the GPS receiver during the previous pass through the

0743processing of Fig. 6B. If so, the vehicle is in the same cell as has been

0744previously processed, and then no further processing for the current cell is required, and the process of Fig. 6B returns. If, however, the vehicle has moved to a new cell, then in step

0745124, the cell number for this new current cell is stored as the prior cell, so that

0746in subsequent passes through the process of Fig. 6B, it will be known whether

0747or not the vehicle has moved to another cell.

0748After step 124, steps are taken to manage "everyday route"

0749modes of the GPS enabled radar detector. As noted above, the user of the GPS

0750enabled radar detector may establish one or more everyday routes traveled by

0751the vehicle and cause the GPS enabled radar detector to, along those routes,

0752continuously update its signal incidence information in the signal information

0753database of Fig. 3. Accordingly, when the GPS enabled radar detector detects

0754that it is following one of these everyday routes, then it will automatically

0755enter its everyday route mode, and subsequently perform different processing

0756(as further described below in connection with Figs. 6C and 6D). As seen in

0757Fig. 6B, each time the GPS enabled radar detector determines in step 122 that

0758it has passed from one cell to another, then (a.) if the detector has been

0759following an everyday route, an evaluation is made whether the GPS enabled

0760radar detector is continuing to follow the previously defined everyday route, or

0761(b.) if the detector has not been following an everyday route, a determination is

0762made whether the GPS enabled radar detector has started following a

0763previously defined everyday route. In the first step of this process, in step 126 it is determined

0764whether the GPS enabled radar detector is already in its "everyday route"

0765mode. If the radar detector is not currently not in its "everyday route" mode,

0766then it is determined whether the radar detector is entering an everyday route;

0767specifically, in step 128, it is determined whether the current cell coordinate is

0768on any of the pre-stored everyday routes. If the current cell is on one of the

0769everyday routes, then the GPS enabled radar detector will determine that the

0770vehicle carrying the detector is beginning or joining one of these pre-stored

0771routes. In such a case, in step 130 the GPS enabled radar detector will enter its

0772"everyday route" mode for the stored route containing the current cell

0773coordinate. If the current coordinate is not on any stored route, step 130 is

0774bypassed.

0775Returning to step 126, if the GPS enabled radar detector is

0776already in its "everyday route" mode, then it is determined whether the

0777detector is continuing to follow this route. In this case, processing proceeds

0778from step 126 to step 132 to determine whether the everyday route is being

0779followed. Specifically, in step 132 it is determined whether the current

0780coordinate is on the current everyday route. If not, then in step 134 the GPS

0781enabled radar detector exits it "everyday route" mode, indicating that the

0782vehicle is no longer on the previously stored everyday route. Otherwise, step

0783134 is bypassed, and the detector remains in its "everyday route" mode. Following step 134 or immediately following step 130,

0784additional steps are performed to determine whether and how to update previously stored signal incidence information in the signal information

0785database of Fig. 3. Processing also proceeds to step 140 from steps 132 or

0786directly from step 128 based upon conditions described above.

0787In step 140 it is determined whether a radar signal is being

0788received by the GPS enabled radar detector. If so, then in step 142 the

0789procedure described below with reference to Fig. 6C is performed to update, as

0790needed, the signal information database of Fig. 3. If no radar signal is being

0791currently detected, then in step 144 the process described below with reference to Fig. 6D is performed to update, as needed, the signal information database

0792of Fig. 3. After step 142 or 144, in step 146 the history database of Fig. 4 is

0793updated by removing the oldest history entry from that database (if necessary

0794to make room), and creating a new history entry for the current cell. The new

0795history entry will include the cell coordinate or a differential coordinate as

0796discussed above with reference to Fig. 4, and would also include a vehicle

0797speed as obtained in step 104 from the GPS receiver or alternatively from an

0798OBD II interface to the vehicle. Following step 146, the processing of the

0799GPS signal is complete. Referring to Fig. 6C, updating of the signal information

0800database of Fig. 3 in the presence of a police radar signal can be elaborated. In the first step 150 it is determined whether the GPS enabled radar detector is in

0801its "signal tracking" mode. The "signal tracking" mode is entered whenever the GPS enabled radar detector is receiving an apparent police radar signal as

0802the detector is passing through space. So long as an apparent police radar

0803signal is being continuously detected, the detector will remain in signal

0804tracking mode in order to associate that police radar signal with all of the

0805geographic locations in which it was detected. It will be appreciated that the process of Fig. 6C will not commence unless there is a police radar signal

0806being detected; therefore, the first step 150 is to determine whether the

0807detector is in its signal tracking mode, and if not, in step 152 to enter the signal

0808tracking mode to thereby begin tracking the police radar signal that had not

0809previously been detected.

0810After step 152 or after step 150 if the detector is already in its

0811signal tracking mode, in step 154 the current cell coordinate and the frequency

0812data for the current cell is stored in a special tracking storage area accessible to

0813fusion processor 22 in EEPROM 34. The frequency data and cell information

0814stored in this tracking storage can be used subsequently to identify the source

0815of the tracked police radar signal more accurately.

0816After step 154, different actions are taken based upon whether

0817the signal information database of Fig. 3 already contains signal information

0818for the detector's current cell coordinate. If there is no matching cells in the signal information database of Fig. 3, then processing continues to step 158 in

0819which it is determined whether the signal information database of Fig. 3 is full,

0820i.e., all the storage space allocated to this database in EEPROM 34 has been

0821consumed. If all the space has been consumed, then in step 160 it is

0822determined whether the GPS enabled radar detector is in its "data overwrite"

0823mode. If so, then the user has identified that current information should be

0824stored for each cell encountered by the vehicle, even when doing so requires

0825the elimination of older stored data. Accordingly, in data overwrite mode,

0826processing proceeds from step 160 to step 162 in which the oldest signal and

0827flag entries in the databases of Figs. 3 and 5 are removed, and then to step 164

0828in which new signal and flag entries are created for the current cell so that

0829signal information and flag information can be stored. If, however, the

0830detector is not in its "data overwrite" mode in step 160, then a warning is

0831delivered to the user that storage of information is being prevented due to the

0832database being full (step 166).

0833After step 166 or 164, or immediately after step 156 if there is

0834already data stored for the current cell, in step 168 it is determined whether the

0835GPS enabled radar detector is in its "training" or "everyday route" mode. As

0836noted above, in these modes, signal information stored in the database of Fig. 3 is continuously updated each time a cell is encountered. Accordingly, if the

0837detector is in either its "training" or "everyday route" mode, then in step 170 the unwanted source incidence counter for each frequency block identified by the radar receiver 24 as containing signal, is incremented, preventing an

0838overflow. Subsequently, in step 172 the unwanted source incidence counter

0839for each frequency block identified by the radar receiver 24 as not having

0840signal, is decremented, preventing an underflow. This thus updates the source

0841incidence counters for each frequency block for the current cell. After this

0842processing, or immediately after step 168 if the GPS enabled radar detector is

0843not in the "training" or "everyday route" mode, updating in step 142 is

0844complete. Referring now to Fig. 6D, processing in step 144, to update

0845various databases when no signal is detected, can be explained. As will be

0846elaborated below, when no police radar signal is being received by the GPS

0847enabled radar detector, this indicates that many of the modes described above

0848for tracking and identifying sources of police radar signal should be

0849terminated.

0850Specifically, in step 180 it is determined whether the GPS

0851enabled radar detector is in "signal tracking" mode. As discussed above, the

0852"signal tracking" mode signifies that the GPS enabled radar detector is

0853currently tracking the cell locations and frequencies of an apparent police radar

0854signal detected by the GPS enabled radar detector. As discussed above with

0855reference to Fig. 6C, step 152, the GPS enabled radar detector will enter "signal tracking" whenever an apparent police radar signal is received. So

0856long as the signal is continuously received, processing of the GPS signal will

0857pass through step 140 of Fig. 6B to Fig. 6C, and "signal tracking" mode will

0858remain engaged. If, however, no police radar signal is being received when

0859processing of the GPS signal passes through step 140 of Fig. 6B, then

0860processing will pass to Fig. 6D and thus to step 180 of Fig. 6D. In the first

0861pass through Fig. 6B after a police radar signal has faded, e.g., due to motion

0862of the vehicle past the source of that signal, "signal tracking" mode will still be

0863engaged as a consequence of prior passes through Figs. 6B and 6C. Thus, if in

0864step 180 of Fig. 6D, if "signal tracking" mode is engaged, but no police radar

0865signal is currently being received, this indicates that the previously detected

0866signal has just faded. In such a situation, a complete record has been made of

0867the locations in which the source was received by the GPS enabled radar

0868detector. This record can be used to characterize the source as to location and

0869frequency, by analyzing the cells in which the signal was tracked, and the

0870frequencies in which the signal was tracked. Thus, if in step 144, the GPS

0871enabled radar detector is "signal tracking" mode, in step 182 the detector exits

0872its "signal tracking" mode. Subsequently, steps are taken to store relevant

0873information collected for the tracked signal.

0874In a first step 184, it is determined whether the GPS enabled

0875radar detector is in "police confirmation" mode. If so, then the vehicle operator has pressed a key on the keypad of the GPS enabled radar detector

0876indicating that a police stakeout was sighted, during the tracking of apparent

0877police radar signals. In such a case, in step 186 the "always warn" flag bit is

0878set for all or the centralmost cells in the tracked sequence of cells identified

0879while in "signal tracking" mode. Thus, the likely locations of the source of the

0880tracked signal are identified and the flag bits are set so that any apparent police

0881radar signal found in those cells will always cause the user to be warned of

0882police radar.

0883If the GPS enabled radar detector is not in "police confirmation" mode, in step 188 it is determined whether the GPS enabled

0884radar detector is in "frequency lockout" mode. As described above, the

0885detector will be in "frequency lockout" mode if the vehicle operator has used

0886the keypad to indicate that any apparent police radar signals that were tracked

0887in the preceding and current cell, are from spurious sources, and that the

0888frequencies in which those spurious signals appeared should be ignored in

0889subsequent passes through the same cell location. Accordingly, if the detector

0890is in "frequency lockout" mode in step 188, processing continues to step 190 in

0891which the lockout bits, in the flag bits 92, are set for all or central cells of the

0892tracked path taken by the vehicle, for those frequencies that were identified during the "signal tracking" mode. After step 190, or immediately after step 188 if the detector is

0893not in "frequency lockout" mode, it is determined whether the receiver is in "location lockout" mode in step 192. It is noted above, "location lockout"

0894mode is engaged by the vehicle operator when broadband sources of spurious produced radar signals are experienced at a geographic location, and the

0895operator wishes to lockout all frequencies at that location. In such a case, in

0896step 194 all of the frequency lockout bits for all or the centralmost cells in the

0897tracked path of the vehicle are set.

0898After step 194, or immediately after step 192 if the detector is

0899not in "location lockout" mode, in step 196 it is determined whether the

0900detector is in "minimal visual" mode. As noted below, the detector will be

0901placed in "minimal visual" mode by the operator when the operator wishes to

0902minimize the indications of police radar signals produced when passing

0903through a geographic region. In such a case, processing continues from step

0904196 to step 198 in which a minimal visual (MV) flag bit is set in the flag

0905database of Fig. 5 for all or the centralmost cells in the tracked path of the

0906vehicle.

0907After step 198, or immediately after step 196 if the detector is

0908not in "minimal visual" mode, or immediately after step 186 if the GPS

0909enabled radar detector is in "police confirmation" mode, in step 200 it is

0910determined whether the signal information database of Fig. 3 includes data for matching or neighboring cells to those cells in the tracked path of the vehicle.

0911If such a match is found, then in step 202 it is determined whether the detector

0912is in its "training" or "everyday route" mode. If so, then the detector should

0913update the stored signal information for the current cell. Specifically, to

0914update signal information, in step 204 all of the unwanted source incidence

0915counters for frequency blocks identified by the receiver are decremented,

0916preventing underflow.

0917Following step 204, or immediately following step 200 if there

0918is no matching signal information or step 202 if the detector is not in its

0919"training" or "everyday route" mode, in step 206 the "frequency lockout",

0920"location lockout", "minimal visual" and "police confirmation" modes are

0921cleared, because the tracking of a police radar signal has ended, and these

0922modes are therefore no longer relevant to the current location of the vehicle.

0923Referring now to Fig. 6E, the processing of keypad activity to

0924enter and exit the various modes described throughout can be explained. As

0925noted with reference to Fig. 6A, various modes are available only if a GPS

0926signal has been obtained from the GPS receiver. If a GPS signal has been

0927obtained then modes are selected from the keypad beginning at step 1 10. If a

0928GPS signal has not been obtained then modes are selected from the keypad

0929beginning at step 114, and a substantial number of modes are disabled and

0930cannot be selected in this circumstance. The keypad activity to select and deselect a mode may vary based upon the application and style of the GPS enabled radar detector. The

0931display and keypad 38 and 36 may interact to produce a menu system for

0932selecting particular modes and displaying associated information.

0933Alternatively, individual keys of keypad 36 may be utilized to directly activate

0934certain modes. Furthermore, display 38 may include icons or other indicators

0935to identify currently activated modes.

0936A first collection of modes that may be activated via the keypad

093736, are the "frequency lockout", "location lockout", and "minimal visual

0938lockout" modes. Through interactions with the keypad in step 210, the user may initiate or terminate these modes. As described above, when initiated,

0939these modes cause lockout information to be stored into flags of the flag

0940database of Fig. 5 upon termination of tracking an apparent police radar signal.

0941If these modes are not engaged at the time that the police radar signal fades

0942from reception, then no action will be taken to set lockout bits in the flag

0943database of Fig. 5. This approach permits a vehicle operator to initiate a

0944lockout mode and then cancel the lockout mode, for example if the operator

0945initially believes a radar signal to be spurious, but then determines that it is in

0946fact being generated by a police source. It will also be noted that, by the operations of Fig. 6D, the "police confirmation" mode will override the

0947"lockout" modes, in that if the "police confirmation" mode is engaged when a police radar signal fades from reception, any "lockout" modes that are engaged

0948will be ignored. The user is not, however, prevented from engaging both modes simultaneously. For example, the user may receive a signal believed to

0949be spurious, and engage a "lockout" mode. The user may then sight a police

0950vehicle and, believing the signal is not spurious, engage "police confirmation"

0951mode. The user may later, however, confirm that the police vehicle is not

0952engaged in a speed trap, and consequently disengage "police confirmation" mode. If the received signal then fades from view, the "lockout" mode will be

0953active and accordingly lockout bits will be set as described above with

0954reference to Fig. 6D.

0955In step 212 the vehicle operator may enter or exit the "training

0956mode", which as described above causes the GPS enabled radar detector to collect signal information for all cells that the vehicle traverses.

0957A third activity that may be undertaken with the keypad, in step

0958214, is to request to clear all lockouts for the current vehicle location. This

0959step may be taken where the GPS enabled radar detector has previously been

0960programmed to lockout a frequency or location and subsequently the vehicle

0961operator sights a police source at that location, and wishes to terminate the

0962lockout at that location. When the vehicle operator requests to clear all

0963existing lockouts, in step 216 the grid coordinates of the vehicle location are

0964compared to all existing members of the flag database of Fig. 5, and all matching and/or neighboring cells are selected and all lockout bits in those

0965cells are cleared.

0966The vehicle operator may also enter or exit a "warning

0967suppression" mode in step 218, in which a warning for a currently tracked

0968police radar signal is suppressed, i.e., so that the detector does not continue to

0969issue warning signals for the same radar signal received. An operator may

0970also enter or exit an "expert meter" mode in step 220, requesting that enhanced

0971information on police radar signals received and/or GPS related lockout

0972information or signal incidence information be displayed on display 38 of the detector. An operator may also enter a "data override" mode in step 222, thus

0973requesting that signal information for new locations visited by the vehicle not

0974found in the database be stored, even at the expense of overriding the oldest

0975previously stored data of this kind. It is also possible, as shown in Fig. 6E,

0976that there may be no keypad activity at the time that operation of the detector

0977passes through step 1 10. In this circumstance, step 224, no further processing

0978is performed.

0979A further action that a vehicle operator may take is to confirm

0980of a police sighting in step 226. This step causes the detector to enter "police

0981confirmation" mode, so that the detector will ensure that police radar signals at

0982the identified stakeout location is handled with particular urgency.

0983Accordingly, when the user enters a police confirmation in step 226, then action is taken to set one for more "always warn" flag bits of the flag database of Fig. 5.

0984If at the time that the operator presses the police confirmation,

0985no apparent police radar signal is currently being tracked, then in step 228 the

0986receiver will not be in "signal tracking" mode. In such a circumstance,

0987processing will continue from step 228 to step 232 in which the "always warn"

0988flag bit is set for the current and neighboring cells of the current location of the

0989vehicle. This step ensures that in future times when a police radar signal is

0990detected in these locations, a warning will be delivered to the vehicle operator

0991regardless of other conditions applicable at the time. If a signal is being

0992tracked at the time that the vehicle operator enters a police confirmation, then

0993a slightly different activity is undertaken. Specifically, in this case processing

0994continues from step 228 to step 230 in which the "police confirmation" mode

0995is entered. As noted above with respect to Fig. 6D, once the receiver is in

0996police confirmation mode, upon termination of signal tracking, central or all

0997cells along the tracked path of the vehicle when the police radar signal was

0998detected, will be marked as "always warn" in the flag database of Fig. 5.

0999A further activity that may be undertaken by a vehicle operator

1000is to indicate that the vehicle is at the beginning of an everyday route, in step

1001240. Doing so causes the GPS enabled radar detector to begin to collect

1002information on the everyday route, for the purpose of ultimately storing a definition of an everyday route to be evaluated in connection with the

1003processing described in connection with Fig. 6B, step 128. When the user

1004indicates that the vehicle is at the beginning of an everyday route, in step 242 the current cell coordinate and the current entry in the vehicle history database

1005of Fig. 4 are stored for later reference. Then in step 244 the detector enters a

1006"route identification" mode, used later in establishing that a route has been

1007identified and is being tracked. When the user wishes to complete an everyday

1008route or wishes to clear everyday route processing for the current vehicle

1009location, the user engages an end or clear operation in step 246. When this

1010step is taken by the user, an initial determination is made in step 248 whether

1011the detector is currently in its "route identification" mode. If so, then the user

1012has identified the end of the everyday route that was previously identified in

1013step 240. Thus, in step 250 it is determined whether the history entry

1014identified and marked in step 242 continues to store the location of the route

1015start that was stored in step 242. If so, then all of the cells accumulated in the

1016vehicle history following the history entry identified in step 242, describe the

1017route taken by the vehicle along the path selected by the user. In this case, all

1018cells accumulated in the history database of Fig. 4 are copied to a special

1019"everyday route" storage area so that all of these cells are available for analysis

1020in connection with the processing of Fig. 6B, step 128. After storing the accumulated history entry cells, in step 252, processing is completed. After step 252, in step 253 the "route identification" mode is exited.

1021If in step 250, it is determined that the vehicle history database

1022of Fig. 4 is no longer storing the start of the everyday route defined by the

1023user, then the everyday route defined by the user was too lengthy to be

1024processed by the GPS enabled radar detector. In such a situation, in step 254

1025the stored route start information is cleared and the "route identification" mode

1026is exited.

1027If in step 248, the GPS enabled radar detector is not in "route

1028identification" mode at the time that the vehicle operator requests the end of everyday route in step 246, then the vehicle operator may wish to delete any

1029everyday route that includes or passes through the current cell. Thus, in step

1030258, a display is generated to the operator requesting confirmation that any

1031everyday route including the current cell should be cleared. If a confirmation

1032is received in step 258, then in step 260 all everyday routes including the

1033current cell are erased from the everyday route storage of the GPS enabled

1034radar detector. If the vehicle operator does not confirm erasure of everyday

1035route information, then processing completes without erasing any everyday

1036route information. In step 1 14 of Fig. 6A, non GPS modes of the GPS enabled

1037radar detector may be activated utilizing keypad activity. This step may be taken if no GPS signal is available at some point during operation of the GPS

1038enabled radar detector. In such a circumstance, in step 262 all GPS related

1039modes of the GPS enabled radar detector are cleared. These include the

1040frequency location and minimal visual lockout modes, the route identification

1041mode, the police confirmation mode, the training mode and the everyday route

1042mode (step 262). After clearing these modes, non GPS related modes of the

1043GPS enabled radar detector can be initiated. These modes include the

1044"warning suppression" mode (step 218), the "expert meter" (step 220), and the

1045"data override" mode (step 222). Other modes that the operator may attempt

1046to select will be ignored so long as no GPS signal is being received.

1047Referring now to Fig. 6F, operations performed in connection

1048with generating audible and visible responses to police radar signals can be

1049explained. In a first step 270, it is determined whether any of a number of

1050lockout or other flags in the flag database of Fig. 5 are applicable to the current

1051cell. In this step 270, the flag database is evaluated to see if there is an entry

1052for the current cell, and if so whether the location lockout, minimal visual

1053lockout or always warn flags in that entry are set. If none of these flags are set,

1054then processing of police radar signals at the current location proceeds based

1055upon information in the signal information database of Fig. 3, or based upon defaults if there is no previously stored information. Accordingly, if none of

1056the flags identified in step 270 are set, then in step 272 it is determined whether there is a cell match in the signal information database of Fig. 3. If

1057there is such a cell match, the frequencies identified by the radar receiver are

1058compared to the signal information in the entry in the database of Fig. 3. In the first step of this process, the first frequency block

1059identified by the receiver is selected (step 274). Then, in step 276, it is

1060determined whether the selected frequency block in the signal information

1061database has a source incidence counter greater than a predetermined "ignore"

1062threshold. If radar signals have been frequently detected in the selected

1063frequency block, but there has never been a police sighting there (and thus the

1064"always warn" flag has never been set), this is strongly indicative of a false

1065source at that location. Accordingly, if the source incidence counter for a

1066frequency block exceeds the "ignore" threshold, then any police radar signals

1067identified in that frequency block are ignored. If, however, the selected

1068frequency block does not have a source incidence counter greater than this

1069threshold, then in step 278 it is determined whether the frequency block has a

1070lockout flag bit set in the flag database of Fig. 5. Only if the frequency lockout

1071bit for the selected frequency is not set, will processing continue to step 280.

1072In step 280 it is determined whether the selected frequency block has a source

1073incidence counter greater than a "silent" threshold. If the source incidence

1074counter exceeds this threshold, then it is likely that there is a false source radar

1075signals at the location, and as a result in step 282 a visual-only response is generated for the frequency band including the selected frequency block. If,

1076however, the selected frequency block does not have a source incidence

1077counter greater than the silent threshold, then an audible and visual response

1078can be generated. In step 284 it is determined whether the receiver is in

1079"warning suppression" mode. If not in this mode, then an audible and visual

1080response is generated for the band of signals including the selected frequency

1081block. Visual response may be a normal response or may be an "expert meter"

1082response depending upon the status of the "expert meter" mode of the receiver.

1083After steps 282 or 284, or immediately after steps 276 or 278 if a frequency block is to be ignored or has been locked out, in step 285 it is

1084determined whether there are additional frequency blocks to be evaluated. If

1085so, then in step 286 the next frequency block is selected and processing returns

1086to step 276. After all frequency blocks have been evaluated, processing ends

1087at step 285, and the generation of audible and visual responses is completed.

1088Returning to step 270, if one of the location lockout, minimal

1089visual lockout or always warn flags are set for the current cell, then in step 290

1090and in step 292 it is determined which of these flags is set. If the "always

1091warn" flag is set for the current cell, then in step 288 an audible and visual

1092response is generated for all frequencies identified by the received, unless

1093suppressed by "warning suppression mode". Step 288 is also performed following step 272 if there is no match for the current cell in the signal information database.

1094If the "minimal visual" flag is set for a current cell, but the

1095"always warn" flag is not, processing proceeds from step 290 to step 292 and

1096then to step 294 in which a minimal visual response is generated for all

1097frequencies identified by the receiver, such as a small blinking flag on the display of the detector.

1098If the "always warn" and "minimal visual" flags are not set, but

1099the "location lockout" flag is set for the current cell, then processing continues

1100from step 270 through steps 290 and 292 to step 296, in which a visual-only

1101response is generated for all frequencies identified by the receiver, which may

1102include expert meter information or other details available from the detector.

1103After step 288, 294 or 296 processing to generate an audible

1104and/or visual response is completed.

1105While the present invention has been illustrated by a

1106description of various embodiments and while these embodiments have been

1107described in considerable detail, it is not the intention of the applicants to

1108restrict or in any way limit the scope of the appended claims to such detail.

1109Additional advantages and modifications will readily appear to those skilled in the art. For example, it will be appreciated that principles of the present

1110invention may also be applied to systems that do not include a GPS receiver.

1111For example, in a simplified embodiment of the present invention, the radar warning receiver may automatically enter its "warning suppression" mode

1112based upon the speed of the vehicle. The speed of the vehicle may, of course,

1113be obtained from a GPS receiver, but if a GPS receiver is not available and/or

1114unnecessarily expensive to include in the receiver, the receiver could obtain

1115vehicle speed information directly from the vehicle's on-board information

1116processing system via the ODB II interface discussed above. A threshold

1117speed of 15 MPH could be used as a default, with "warning suppression" mode

1118automatically engaged at speeds below this threshold. This threshold may be

1119user-adjustable, e.g., within a range such as 5 to 50 MPH.

1120The interface connector used by the receiver may take other

1121forms than the known USB standard. It may use any computer interface

1122standard (e.g., IEEE 488), or an automotive wiring standard, the Jl 854, CAN.

1123BH12 and LIN standards, or others.

1124In a more refined embodiment, a "everyday route" mode could

1125be included, in which the operator can perform "everyday route velocity"

1126training. In this "everyday route velocity" training mode, the vehicle speed at

1127each point along the "everyday route" would be stored along with the cell

1128locations along the route. Subsequently, when the detector determines that it is on a previously defined everyday route, it will enter "warning suppression"

1129mode whenever the vehicle speed is within a tolerance of, or below, the

1130velocity recorded when in "everyday route velocity" training mode. Thus, no

1131warning signals will be generated so long as the vehicle is not traveling faster

1132than the threshold speed identified by the operator during "everyday route

1133velocity" training of the detector.

1134It will be further appreciated that the "signal tracking" mode

1135described herein may operate upon each frequency band independently, so that

1136the "signal tracking" mode may be engaged for one band while disengaged for others, and so that the fade-out of a tracked signal at one frequency will cause

1137flag bits to be set for that frequency while other frequencies continue to be

1138tracked.

1139It will be further appreciated that the determination of whether

1140to generate an audible or visual response, or both, may be based on

1141information in addition to the flags applicable to the current cell of the vehicle.

1142For example, the flags in cells recently traversed by the vehicle may also be

1143consulted to determine whether audible or visual signals should be suppressed

1144at a current cell. Thus, for example, if the detector passes through a cell that

1145has been marked for "minimal visual" lockout, warnings will be suppressed for subsequent cells entered by the vehicle while the same signal is being tracked,

1146regardless of whether flag bits in those cells call for a lockout. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative

1147example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general

1148inventive concept.

1149What is claimed is: