Electronic house arrest system having officer safety reporting feature

What is claimed is:

1. An electronic house arrest monitoring (EHAM) system for monitoring the presence or absence of an offender at a prescribed location remote from a central monitoring location, comprising:

a tag carried by the offender, said tag having transmitter means therein for generating and transmitting a first multi-bit identification (ID) signal at low power, and hence over a short range, said first ID signal including a particular combination of bits that uniquely identifies the offender to whom the tag has been assigned;

a triggerable portable transmitter carried by an officer who visits the offender at the prescribed location, said triggerable portable transmitter including means for manually triggering the generation and transmission of a second multi-bit ID signal upon manual activation of a transmit switch, said second ID signal including a prescribed combination of bits that identifies a situation wherein the officer believes back-up assistance may be needed at the prescribed location;

an in-house monitoring unit at the prescribed location, said IMU including a receiver for receiving said first and second ID signals, and processing means for examining said received first and second ID signals and responding to said first ID signal with a first response and to said second ID signal with a second response different than said first response;

a central processing unit at the central monitoring location;

means for selectively establishing telecommunicative contact between said IMU and CPU;

said second response of said IMU including means for notifying said CPU of the receipt of said second ID signal through said established telecommunicative contact, and providing said CPU with information that identifies the prescribed location at which the second ID signal was received, whereupon appropriate action may be taken to dispatch back-up assistance to said prescribed location.

2. The EHAM system as set forth in claim 1 wherein said triggerable portable transmitter includes an activation switch that can be activated by said officer whenever the officer desires to trigger the generation and transmission of said second ID signal.

3. The EHAM system as set forth in claim 2 wherein said triggerable portable transmitter includes means for generating and transmitting said second ID signal at least n times, where n is an integer greater than one, upon activation of said activation switch.

4. The EHAM system as set forth in claim 2 wherein said activation switch comprises first and second push buttons connected in series, both of which must be simultaneously activated in order to trigger the generation and transmission of said second ID signal.

5. The EHAM system as set forth in claim 4 wherein said triggerable portable transmitter is housed in an enclosed housing that readily fits within a pocket of the clothing of said officer, whereby said transmitter may be concealed as said officer visits said prescribed location, said first push button being located on a first surface of said housing, and said second push button being located on a surface of said housing other than said first surface.

6. The EHAM system as set forth in claim 1 wherein said first and second multi-bit ID signals each comprise a radio frequency (RF) carrier signal that is modulated with at least 32 bits of information.

7. The EHAM system as set forth in claim 6 wherein said RF carrier signal of said first and second multi-bit ID signals is amplitude modulated with a sequence of 32 to 64 bits of information, said sequence of bits including a start bit sequence, a stop bit sequence, error correction bits, and ID code bits.

8. The EHAM system as set forth in claim 6 wherein the frequency of the RF carrier signal of both said first and second multi-bit ID signals is within the range of approximately 908 to 928 MHz.

9. A portable transmitter for use with an electronic house arrest monitoring (EHAM) system, said EHAM system including means for electronically monitoring the presence or absence of an offender at a prescribed location, said EHAM system including an in-house monitoring unit (IMU) at the prescribed location that is capable of establishing telecommunicative contact with a central monitoring station, said IMU further including means for communicating to said central monitoring station through said established telecommunicative contact an information signal that identifies a particular IMU and that indicates the presence or absence of the offender at the prescribed location, said portable transmitter comprising:

a radio frequency (RF) oscillator that generates and transmits an RF signal;

modulating means for modulating said RF signal with a multiplicity of bits of information, a subset of said bits including a prescribed first code that identifies a need for assistance; and

a switch responsive to manual activation that when activated causes said modulated RF signal to be transmitted by said transmitting means;

said transmitted modulated RF signal being receivable within a receiver circuit of said IU if said portable transmitter is in the vicinity of said IMU, whereby an officer carrying said portable transmitter can visit the offender at said prescribed location and manually activate the switch if a potential need for assistance is detected, thereby causing said first code to be included in the modulated RF signal that is transmitted by said portable transmitter, which first code is detected in the modulated RF signal received by the IMU receiver causes said IMU receiver to respond differently than the IMU receiver responds when electronically confirming the presence of the offender at the prescribed location.

10. The portable transmitter as set forth in claim 9 wherein said switch includes first and second push-button switches connected in series, both of which must be simultaneously depressed in order to cause said modulated RF signal to be transmitted.

11. The portable transmitter as set forth in claim 9 wherein said portable transmitter includes means for transmitting said modulated RF signal a multiplicity of times upon a single activation of said switch.

12. The portable transmitter as set forth in claim 9 further including power control means responsive to said switch for selectively applying operating power to said RF oscillator.

13. The portable transmitter as set forth in claim 9 wherein the RF oscillator, modulating means, and switch are all housed in a small enclosed housing that allows the transmitter to be readily hidden as it is carried by the officer, said first and second push-button switches being accessible for activation from different sides of said housing.

14. The portable transmitter as set forth in claim 9 wherein said modulating means includes means for modulating said RF signal with at least 32 bits of information, said at least 32 bits including a start bit sequence, a stop bit sequence, error correction bits, and said prescribed first code that identifies a need for assistance.

15. The portable transmitter as set forth in claim 14 wherein said modulating means comprises a microprocessor circuit coupled to a memory circuit, said at least 32 bits of information being programmably stored in said memory circuit.

16. The portable transmitter as set forth in claim 15 wherein the frequency of said RF signal falls within the range of 908-928 MHz.

17. A method of protecting an officer who is visiting offenders in the field, said offenders being monitored with an electronic house arrest monitoring (EHAM) system, said EHAM system including a plurality of in-house monitoring units (IMUs) respectively installed at or positioned near prescribed field locations, each of said IMUs being at a known field location, and each including means for electronically monitoring its respective field location for the presence or absence of the offender, each IMU further including means for establishing telecommunicative contact with a central monitoring station and electronically reporting the results of such monitoring, said method comprising the steps of:

(a) providing said officer with a portable transmitter, said portable transmitter including means for selectively generating and transmitting an electronic signal, said electronic signal including a first code that identifies a need for back-up assistance, said electronic signal being receivable by an IMU that is within a few hundred feet of said portable transmitter at the time of said electronic signal is generated;

(b) triggering the transmission of said electronic signal whenever said officer perceives that back-up assistance may be needed at a particular field location whereat the officer is visiting, said electronic signal being received within the IMU at the location where the officer is visiting;

(c) verifying the presence of said first code in the electronic signal received within the IMU;

(d) responding to the verification performed in step (b) in a way that is different from the electronically reporting response of the IMU when monitoring the presence or absence of the offender at the prescribed location, said response to the verification performed in step (b) including automatically establishing telecommunicative contact with the central monitoring station;

(e) electronically notifying the central monitoring station through said telecommunicative contact of the identity of the particular IMU at which the first code was received and verified; and

(f) determining the location of the particular IMU whereat the first code was received and dispatching back-up assistance to the determined location.

18. The method of protecting an officer as set forth in claim 17 wherein the processing of the received electronic signal within the IMU to determine the presence of said first code comprises:

checking the received electronic signal for the presence of an identification (ID) code;

if an ID code is present, verifying if said ID code is a valid first code; and

modifying said ID code to include information that indicates the date and time at which the ID code was received;

said date and time information being thereafter forwarded to said central monitoring station along with the identity of the particular IMU that received the electronic signal.

19. The method of protecting an officer as set forth in claim 18 further including electronically storing the modified ID code within the IMU, and thereafter reporting the date and time information included in said stored modified ID code, as well as the identity of the particular IMU wherein the ID code is stored, to said central monitoring station through the established telecommunicative link.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

The present invention relates to a personnel monitoring system, and more particularly to a house arrest monitoring system wherein individuals who wear a special tag can be electronically monitored for compliance with a court-ordered sentence (or similar restriction) requiring them to remain at a specified location(s) at a specified time(s). Even more particularly, the present invention relates to such an electronic house arrest system wherein a monitoring officer, e.g., a probation or parole officer responsible for making periodic and/or random physical checks with the individuals being monitored at or near the specified monitoring location(s), can immediately and silently report to a central monitoring location that backup help or assistance is needed at such location.

Electronic house arrest monitoring (EHAM) systems are known in the art. Such systems fulfill a valuable need in that they allow a relatively large number of individuals who have been ordered by a court to remain under house arrest, or who are under parole or probation requirements to remain at certain locations at specified times, to be electronically monitored for compliance with whatever restrictions have been imposed. Such electronic monitoring can advantageously be carried out at a fraction of the cost of incarceration of the monitored individuals; and also at a much reduced cost over conventional probation/parole monitoring procedures. Further, an electronic monitoring system offers the advantage of reducing the physical contact between a monitoring officer, e.g., a probation or parole officer, and the monitored individual, which physical contact can, at certain times and certain locations, pose a potential danger to the officer.

One type of house arrest monitoring system known in the art, referred to as an "active" monitoring system, generates and transmits radio wave signals as part of the monitoring process. Such an active EHAM system is described, e.g., in U.S. Pat. No. 4,918,432, issued to Pauley et al. In the Pauley et al. active EHAM system, each individual being monitored is fitted with an electronic bracelet or anklet. Such bracelet or anklet, referred to in the referenced patent as a "tag", includes a transmitter that periodically transmits a identifying radio wave signal (unique to each tag, and hence to each individual) over a short range (e.g., 150 feet). A field monitoring device (FMD) is installed at each location where the monitored individual(s) is supposed to be. If the monitored individual(s) is present at the FMD location, a receiver circuit within the FMD receives the unique identifying signal. The FMD processing circuits can thus determine that a specific individual is present at the location of the FMD when the signal is received. This information (which may be considered as "presence data") is stored within the FMD memory circuits for subsequent downloading to a central monitoring location. A computer, or central processing unit (CPU), located at the central monitoring location periodically or randomly polls the various FMD locations through an established telecommunicative link, e.g., through standard telephone lines, in order to prepare reports indicating the presence or absence of the individuals at the specified locations. Such reports are then used by the agency charged with the responsibility for monitoring the individuals to ascertain whether or not such the monitored individuals are in compliance with whatever restrictions have been imposed.

An important feature of the Pauley et al. EHAM system is the ability of the tag to detect any attempts to tamper with it, e.g., to remove the tag from the monitored individual. If a tamper event is detected, such occurrence is immediately signaled to the FMD, and the FMD, in turn, includes the ability to immediately establish telecommunicative contact with the central CPU in order to report such tamper event. All data sent from the FMD to the central CPU includes address-identifying data that identifies the specific location where the FMD is located. The '432 Pauley et al. patent is incorporated herein by reference.

Other active EHAM systems known in the art also include the ability to detect tamper events, such as U.S. Pat. No. 4,777,477, issued to Watson, wherein any attempt to cut or break the strap that attaches the tag to the individual is detected and signaled to a local receiver. The '477 Watson patent is also incorporated herein by reference.

Still other active EHAM systems known in the art include the ability to adaptively change the monitoring configuration to best suit the needs of the agency responsible for carrying out the monitoring function. See U.S. Pat. No. 4,952,928 issued to Carroll et al., which patent is likewise incorporated herein by reference. The Carroll et al. system advantageously includes the ability to sense and monitor various physiological data of the monitored individual, such as heart rate, blood pressure, body position (horizontal or vertical), and the like, so that such data can be analyzed at the central monitoring location to determine if the monitored individual is complying with other restrictions, such as abstinence from drugs or alcohol.

Another type of electronic house arrest system known in the art is a "passive" monitoring system. A passive system typically does not involve the generation and transmission of radio wave signals, such as are used in the active EHAM systems. An example of a passive system is disclosed in U.S. Pat. No. 4,747,120, issued to Foley. In the Foley system, a central computer randomly establishes telephonic contact with a specific location whereat the monitored individual is supposed to be at a time when such individual is supposed to be there. The computer then instructs the individual, e.g., using synthetically generated speech, to perform some act, such as inserting a specially coded wristlet permanently affixed to the individual (and hence unique to the individual) into a decoding device interconnected with a telephone at the remote location. If the individual successfully completes the act, which act is designed to be something that only the correct individual can successfully do, then a verify signal is sent back to the central computer over the telephone lines and the computer thus determines that the correct individual is at the remote location. If the verify signal is not received, then the computer determines that the correct individual is not at the specified location.

Another type of passive EHAM system known in the art includes the ability to also test the monitored individual for compliance with other restrictions, in addition to staying at a specified location, such as abstinence from alcohol and drugs. See, e.g, U.S. Pat. No. 4,843,377, issued to Fuller et al. In such systems, a breathalyzer device is coupled to the telephone line. If the blood alcohol level of the monitored individual exceeds prescribed limits, then an appropriate signal indicating this fact is sent to the central monitoring location. One embodiment of the system disclosed in the Fuller et al. patent includes the use of a camera at the remote location. The picture of the monitored individual is converted to electronic data and transmitted to the central location, i.e., over the telephone lines, where it is reconstructed so that the image of the monitored individual can also be checked.

Regardless of the type of EHAM system employed, whether passive, active, or combinations of active and passive, there frequently arises a need for a monitoring officer, or other individual from the monitoring agency, to physically go to the monitoring location and verify that the monitored individual is in fact at the monitored location, and that other restrictions that may have been imposed are being complied with. At other times, visits must be made to the field to check out the operation of the monitoring equipment. When this need arises, the monitoring officer, in going to the monitored location, may place himself or herself in danger of bodily harm, either directly from the monitored individual (who may be drunk, or under the influence of drugs), or from other individuals in the same neighborhood as the monitored individual. What is needed, therefore, is an EHAM system that provides the monitoring officer some measure of security and protection as such field visits are made.

One technique known in the art for providing officer safety is to require that a team of officers, e.g, at least two officers, perform the actual visit to the monitoring location. The team of officers can then use established procedures commonly practiced by law enforcement agencies to assure the safety of the officers involved, including carrying firearms and other weapons. Unfortunately, many monitoring agencies do not have the budget nor the manpower to dispatch a team of officers to a specified location to follow up on compliance with mandated restrictions. Further, a team of officers may intimidate the monitored individual, particularly if they are carrying firearms, and prevent the free flow of information that the monitoring officer may need. Hence, what is needed is an EHAM system that does not require a team of monitoring officers to check up on compliance with mandated restrictions, and that facilitates a single officer making such visits. However, should a dangerous situation develop, there is also a need for an EHAM system that allows an appropriate team of law enforcement officers, e.g., police or sheriff officers from the closest station, to be immediately dispatched to the location where the dangerous situation exists.

Another technique used in the art to provide a measure of safety for the monitoring officer is to require the monitored individual to step outside, e.g., on the front porch or otherwise in front of the monitored location, so that the monitoring officer can readily see, and even talk with, the individual from the relative safety of his or her automobile. In this way, the officer can simply "drive by" the monitored location without having to physically enter the premises. One drive-by system even provides a means for issuing an electronic "callout" signal to the monitored individual, so that he or she knows the officer is outside, and that the monitored individual must thus step outside so that the monitored individual can be seen by the officer. See, e.g., U.S. Pat. No. 4,924,211, issued to Davies et al. Unfortunately, requiring the monitored individual to always step outside of his premises may preclude the monitoring officer from discovering some necessary information needed to properly ascertain if the individual is in full compliance with the mandated restrictions of the house arrest. Hence, what is needed is an EHAM system that allows the officer to enter the premises of the monitored individual, and still provides some measure of protection while there.

SUMMARY OF THE INVENTION

The present invention advantageously provides an EHAM system that addresses the above and other needs. In accordance with one aspect of the invention, a house arrest monitoring system allows a monitoring officer, e.g., a probation or parole officer, charged with the responsibility of making periodic and/or random physical checks with individuals whose presence at specific locations is being electronically monitored (hereafter the "offender"), to immediately and silently report to a central monitoring location that backup help or assistance is needed at the monitoring location.

One embodiment of the electronic house arrest system of the present invention, like active EHAM systems of the prior art, includes a field monitoring unit (FMU), or equivalent, installed at specific monitoring locations. A monitored individual, i.e., the offender, wears an electronic tag that periodically transmits a unique identifying signal over a short range. If the offender is within range of the FMU, the identifying signal is received by a receiver within the FMU, and logged or stored within memory circuits of the FMU, indicating the presence of the offender at the specific location of the FMU at the time the signal is received. Periodically, or randomly, telecommunicative contact is established between the FMU and a computer at a central monitoring location, and the "presence data" stored in the FMU, i.e., that data indicating when the identifying signal is received, is downloaded to the central computer, along with FMU-identifying data, indicating the specific FMU --and hence the specific address or location of the FMU-- from which the presence data is obtained. From this downloaded data, the computer is able to generate reports and other data indicating whether the offender is in compliance with the particular house arrest restrictions that have been imposed.

Unlike EHAM systems of the prior art, however, the present invention includes a small pocket transmitter that is carried by the monitoring officer. When the monitoring officer goes into the field to physically visit with a particular offender, this pocket transmitter is always at the officer's fingertips. If the officer senses danger or otherwise needs backup assistance at or near a monitored location, the officer silently activates a transmit button or switch on the pocket transmitter, which action causes a universal "needs assistance" signal to be transmitted. The "needs assistance" signal, which may also be referred to hereinafter as an "officer assist" signal, is received by the FMU at the monitored location. The processing circuits of the FMU react to receipt of the "needs assistance" signal by immediately establishing telecommunicative contact with the computer at the central monitoring location, and sending to the computer an indication that the "needs assistance" signal has been received through a particular FMU. The computer is able to identify the particular FMU through FMU-identifying data that is also sent to the computer once telecommunicative contact is established between the FMU and the computer. The central computer, upon receipt of the "needs assistance" signal and the FMU-identifying data, looks up the address assigned to the identified FMU, and immediately takes appropriate action to cause backup assistance to be dispatched to the identified address.

Another embodiment of the invention includes a special portable receiver carried in the automobile of the officer. The receiver is able to detect any identifying signal transmitted by the offender tag when the officer drives by the location where the offender is supposed to be. If the officer needs to inspect or visit the offender, the automobile is parked near the residence of the offender, and the officer carries the small pocket transmitter, as described above, as such visit is made. If the officer senses danger, the officer silently activates the transmit button on the pocket transmitter, causing the "officer assist" signal to be transmitted. The officer assist signal is received at the portable receiver carried in the officer's automobile. The portable receiver is configured, upon receipt of the officer assist signal, to alert a companion of the officer (who is waiting in the car). Alternatively, in some embodiments, the receiver responds to the officer assist signal by automatically establishing radio contact with the appropriate dispatch location, and alerting the dispatch office of the officer assist situation. This embodiment of the invention thus allows the officer some measure of protection even when the premises being visited does not include an FMU, or equivalent, installed at the offender's residence to electronically monitor the offender.

Thus, the present invention may be characterized as a portable transmitter for use with an electronic house arrest monitoring (EHAM) system or other monitoring program. Such EHAM system, like EHAM systems of the prior art, includes means for electronically monitoring the presence or absence of an offender at a prescribed location. This is done through use of an in-house monitoring unit (IMU), or equivalent, that is placed at the prescribed location. In some embodiments, as indicated above, the equivalent of the IMU may be carried in the officer's automobile. Such IMU is capable of establishing telecommunicative contact with a central monitoring station. Further, the IMU typically includes means for generating and sending an information signal to the central monitoring station through the established telecommunicative contact that identifies a particular IMU and indicates whether the presence of the offender has been detected at the prescribed location.

A portable transmitter in accordance with this embodiment of the invention includes: (1) a radio frequency (RF) oscillator that generates an RF signal; (2) modulating means for modulating the RF signal with a multiplicity of bits of information, e.g., at least 32 bits of information, a subset of these bits including a prescribed first code that identifies a need for assistance; (3) transmitting means for selectively transmitting the modulated RF signal, and (4) switch a responsive to manual activation for controlling the modulated RF signal to be transmitted by the transmitting means.

Advantageously, the transmitted modulated RF signal generated by the portable transmitter is receivable within a receiver circuit of the IMU if the portable transmitter is in the vicinity of the IMU when the modulated RF signal is transmitted. Thus, an officer carrying the portable transmitter can visit the offender at the prescribed location and manually activate the switch means if a potential need for assistance is detected. If so, such activation causes the first code to be transmitted in the modulated RF signal. If this first code is detected in the modulated RF signal that is received by the IMU receiver, the IMU receiver responds differently than the IMU receiver responds when electronically confirming the presence of the offender at the prescribed location. Specifically, the IMU receiver immediately communicates the need-for-assistance information evidenced by receipt of the first code to the central monitoring station. In this way the central monitoring station is made aware of a need for assistance at the prescribed location where the particular IMU is located.

Another embodiment of the invention may be characterized as an electronic house arrest monitoring (EHAM) system used for monitoring the presence or absence of an offender at a prescribed location remote from a central monitoring location. Such EHAM system includes, as do EHAM systems of the prior art, a tag carried by the offender. This tag includes transmitter means for generating and transmitting a first multi-bit identification (ID) signal at low power, and hence over a short range. This first ID signal includes a particular combination of bits that uniquely identifies the offender to whom the tag has been assigned.

Unlike EHAM systems of the prior art, the EHAM system in accordance with this embodiment of the invention also includes a triggerable portable transmitter carried by an officer who visits the offender at the prescribed location. This triggerable portable transmitter includes means for manually triggering the generation and transmission of a second multi-bit ID signal upon manual activation of a transmit switch. This second ID signal includes a prescribed combination of bits that identifies an "officer assist" situation, i.e., a situation wherein the officer believes back-up assistance may be needed at the prescribed location based on what the officer sees or senses at the prescribed location.

The EHAM system further includes an in-house monitoring unit (IMU), or equivalent, at the prescribed location, or carried in the officers automobile so it can be positioned near the prescribed location. Such IMU includes a receiver for receiving the first and second ID signals. The IMU additionally includes processing means for examining the received first and second ID signals to determine the particular combination of bits contained therein, and hence to determine whether the offender is at the prescribed location or whether the officer has signaled that back-up assistance may be needed. The IMU thus responds differently to receipt of the first ID signal than it does to receipt of the second ID signal.

The EHAM system also includes a central processing unit (CPU) at the central monitoring location, and means for selectively establishing telecommunicative contact between the IMU and CPU. In particular, the IMU includes means for notifying the CPU of the receipt of the second ID signal through the established telecommunicative contact, and providing the CPU with information that identifies the prescribed location at which the second ID signal was received. Upon such notification at the central monitoring location, appropriate action may then be taken to dispatch back-up assistance to the prescribed location. Hence, the officer is able to "silently" signal the central monitoring station that backup assistance may be needed at a particular location where the officer is visiting an offender.

Another embodiment of the invention may be characterized as a method of protecting an officer who is visiting offenders in the field. Such offenders are monitored with an electronic house arrest monitoring (EHAM) system of the type described above. That is, the EHAM system includes a plurality of in-house monitoring units (IMUs), or equivalent, respectively installed at or positioned near prescribed field locations, each of the IMUs being at a known field location, and each including means for electronically monitoring its respective field location for the presence or absence of the offender. Each IMU further includes means for establishing telecommunicative contact with a central monitoring station and electronically reporting the results of such monitoring. The officer protection method includes the following steps:

(1) Providing the officer with a portable transmitter. Such portable transmitter includes means for selectively generating and transmitting an electronic signal that includes a first code that identifies a need for back-up assistance. This electronic signal is receivable by an IMU that is within a few hundred feet of the portable transmitter at the time the electronic signal is generated.

(2) Triggering the transmission of the electronic signal whenever the officer perceives that back-up assistance may be needed at a particular field location where the officer is visiting. This electronic signal is then received within the IMU at that field location.

(3) Verifying the presence of the first code in the electronic signal received within the IMU.

(4) Responding to the verification in a way that is different from the electronically reporting response of the IMU when monitoring the presence or absence of the offender at the prescribed location by automatically establishing telecommunicative contact with the central monitoring station.

(5) Electronically notifying the central monitoring station through the telecommunicative contact of the identity of the particular IMU at which the first code was received.

(6) Determining the location of the officer in the field from the identity of the particular IMU where the first code was received.

(7) Dispatching back-up assistance to the determined location of the officer in the field.

It is thus a feature of the present invention to provide an EHAM system that provides the monitoring officer some measure of security or protection as he or she makes visits with offenders in the field.

It is an additional feature of the invention to provide an EHAM system that allows an officer to effectively be in continuous telecommunicative contact with backup assistance while making visits with offenders in the field, thereby allowing the officer to make such visits near or in the residence of the offender so long as a field monitoring unit, or equivalent, is located at the location where the visit is made.

It is another feature of the invention to provide such an EHAM system that does not require a team of monitoring officers to make visits with offenders in the field in order to safely check compliance with mandated restrictions. Rather, the EHAM system of the present invention facilitates a single officer making such visits. Should a dangerous situation develop, however, it is a further feature of the present invention to provide a means whereby such dangerous situation can be immediately reported by the officer to appropriate law enforcement authorities. In response, a team of law enforcement officers, e.g., police or sheriff officers from the nearest available location, can be immediately dispatched to the location where the dangerous situation has developed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

FIG. 1 is a block diagram of an EHAM system, that includes a portable officer transmitter;

FIG. 2 is a block diagram of the officer transmitter of the EHAM system of FIG. 1;

FIG. 3 is a diagrammatic representation of the identification signal, or ID signal, that is transmitted from the officer transmitter;

FIG. 4 is a perspective view of the officer transmitter housing;

FIG. 5 is a simplified block diagram of the in-house monitoring unit, or IMU, used with the system of FIG. 1; and

FIG. 6 is a flow chart illustrating one type of monitoring program that may be used to control the processor of the IMU.

Like reference numerals are used to represent like elements in the various figures and the accompanying description that follows.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.

Referring first to FIG. 1, there is shown a block diagram of an electronic house arrest monitoring (EHAM) system 12 made in accordance with the present invention. The EHAM system 12 includes a portable officer transmitter 14, and an in-house monitoring unit (IMU) 16, or equivalent. The IMU 16 is located at a particular remote monitoring location 18. Typically, the remote monitoring location 18 comprises a house whereat the individual to be monitored, the "offender", resides. However, any location, such as a place of work or school, may also be utilized as a remote monitoring location. Further, although the description presented below is for an embodiment of the invention that includes an IMU 30 installed at the remote monitoring location 18, it is to be understood that the invention also has applicability to other embodiments, such as where the equivalent of the IMU is carried in an automobile that drives by the remote monitoring location to determine if the offender is there.

The offender is fitted with an offender tag 20. Typically, the tag 20 is fitted around the ankle or wrist of the offender with a strap or band that cannot be removed. Any attempt to cut or remove the strap, i.e., to remove the tag from the offender, is detected by the circuits within the tag, as described, e.g., in the Pauley et al. or Watson patents cited above. Any such attempt to remove the tag from the offender is treated as a "tamper event", and the occurrence of any tamper event is immediately signaled to the IMU 16.

For active EHAM systems, as described above, the tag 20 periodically, e.g., every 10-120 seconds, transmits an identification (ID) signal 22. The ID signal 22 transmitted from the tag is symbolically represented in FIG. 1 as a wavy arrow 22. The ID signal is typically a digitally modulated radio frequency (RF) signal, containing a multiplicity of bits. This modulated RF signal is transmitted from the tag 20 at low power, and hence over a short range. Typically, the boundaries of the monitoring location 18 are determined by the range of the ID signal. Thus, whenever the tag is sufficiently distant from the IMU 16 so that the ID signal is not received, i.e., is out of range, then the offender is not considered as being at the house arrest location.

Some of the bits of the ID signal 22 are used as an "ID code" to uniquely identify a particular tag, and hence a particular offender to whom