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Claims  |
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What is claimed is:
1. A system for monitoring the presence or absence of an individual within
a defined area, said system comprising:
(a) an identification tag that is attached to the individual, said
identification tag including:
a first power source,
sensing means for sensing prescribed conditions associated with the
operation and use of said tag, and
means coupled to said first power source for periodically transmitting in
short data bursts an identification signal including identification
information that uniquely identifies said tag, and hence the individual to
whom the tag is attached, and status information that indicates the
prescribed conditions sensed by said sensing means;
(b) receiving means positioned within said defined area for receiving said
identification signal;
(c) processing means coupled to said receiving means for noting the time of
receipt and content of the received identification signals, from which
time and content information a determination can be made as to the
presence or absence of the individual within the defined area during any
given time period; and
(d) tamper means included within said processing means for sensing one of a
plurality of tamper conditions associated with the use of said processing
means and for generating a tamper condition signal in the event that one
of said plurality of tamper conditions occurs.
2. The monitoring system of claim 1 wherein the prescribed conditions
sensed by said sensing means include whether the tag has remained attached
to the individual.
3. The monitoring system of claim 1 wherein said sensing means comprises
means for holding the tag near the skin or flesh of the individual; and
first circuit means for sensing the presence or absence of said skin or
flesh near said tag.
4. The monitoring system of claim 3 wherein said holding means comprises a
conductive strap attached to said tag that fits around a limb of said
individual and holds the tag against said limb.
5. The monitoring system of claim 4 wherein said sensing means further
comprises second circuit means for sensing the continuity of said
conductive strap, whereby the cutting or breaking of said strap can be
sensed.
6. The monitoring system of claim 3 wherein said first circuit means
comprises means for sensing a change in the coupling present between a
surface of the tag and the skin or flesh of the individual.
7. The monitoring system of claim 1 wherein said processing means
comprises:
field processing means located at a fixed location within said defined area
and connected to said receiving means for initially processing, storing
and monitoring the information contained in said identification signal,
said field processing means having said tamper means included therewithin;
and
central processing means, selectively coupled to said field processing
means, for processing, storing and monitoring information received from
said field processing means, said central processing means being located
remote from said defined area.
8. The monitoring system of claim 7 where said field processing means
includes mode control means for switching the operation of said field
processing means from a sleep mode to an awake mode whenever one of a
plurality of prescribed events occurs, said prescribed events including
the receipt of data by said receiving means, the detection by said tamper
means of one of said plurality of tamper conditions, and the timing out of
a sleep period.
9. The monitoring system of claim 8 wherein said sleep period comprises
approximately 120 seconds.
10. The monitoring system of claim 7 wherein said field processing means is
selectively coupled to said central processing means through a telephone
line, and wherein the central processing means includes dialing means for
automatically dialing up said field processing means, and said field
processing means includes answering means for automatically responding to
the dialing means of said central processing means, whereby a connection
can be established between said central processing means and said field
processing means as controlled by said central processing means.
11. The monitoring system of claim 10 wherein said field processing means
also includes dialing means and said central processing means include
answering means for establishing a connection between said field
processing means and said central processing means as controlled by said
field processing means.
12. The monitoring system of claim 11 wherein said plurality of tamper
conditions sensed by said tamper means of said field processing means
includes a phone line tamper detect circuit.
13. The monitoring system of claim 10 wherein said central processing means
includes polling means for randomly dialing up a plurality of said field
processing means positioned at different locations remote from said
central processing means.
14. The monitoring system of claim 13 wherein said central processing means
includes report generating means for generating reports based on the
information received from each field processing means.
15. The monitoring system of claim 1 wherein said means for periodically
transmitting said identification signal includes stable radio frequency
(RF) generating means for generating an RF carrier signal at a prescribed
frequency for a short period of time, said RF carrier signal being
modulated by the identification information and status information.
16. The monitoring system of claim 15 wherein said receiving means includes
at least two spaced-apart receiving antennas, the distance between any two
antennas being selected as a function of the wavelength of the prescribed
frequency of said RF carrier signal.
17. The monitoring system of claim 1 further including repeater means
selectively positioned within said defined area for receiving said
identification signal and, after a prescribed delay, retransmitting said
identification signal to said receiving means.
18. A system for monitoring the presence or absence of an individual within
a defined area, said system comprising:
(a) an identification tag that is attached to the individual, said
identification tag including:
a first power source,
sensing means for sensing prescribed conditions associated with the
operation and use of said tag, and
means coupled to said first power source for periodically transmitting in
short data bursts an identification signal including identification
information that uniquely identifies said tag, and hence the individual to
whom the tag is attached, and status information that indicates the
prescribed conditions sensed by said sensing means, said transmitting
means including stable radio frequency (RF) generating means for
generating an RF carrier signal at a prescribed frequency, said RF carrier
signal being modulated by the identification information and status
information;
(b) receiving means positioned within said defined area for receiving said
identification signal, said receiving means including at least two
spaced-apart receiving antennas, the distance between any two antennas
being selected as a function of the wavelength of the prescribed frequency
of said RF carrier signal, said receiving means further including means
for connecting only one of said at least two spaced-apart receiving
antennas to an RF receiving circuit at any instant of time, all of said at
least two spaced-apart receiving antennas having respective time periods
for being connected to said RF receiving circuit;
(c) processing means coupled to said receiving means for noting the time of
receipt and content of the received identification signals, from which
time and content information a determination can be made as to the
presence or absence of the individual within the defined area during any
given time period; and
(d) tamper means included within said processing means for sensing one of a
plurality of tamper conditions associated with the use of said processing
means and for generating a tamper condition signal in the event that one
of said plurality of tamper conditions occurs.
19. A system for monitoring the presence or absence of an individual within
a defined area, said system comprising:
(a) an identification tag that is attached to the individual, said
identification tag including
a first power source,
sensing means for sensing prescribed conditions associated with the
operation and use of said tag, and
means coupled to said first power source for periodically transmitting in
short data bursts an identification signal including identification
information that uniquely identifies said tag, and hence the individual to
whom the tag is attached, and status information that indicates the
prescribed conditions sensed by said sensing means;
(b) repeater means selectively positioned within said defined area for
receiving said identification signal and, after a prescribed delay,
retransmitting said identification signal to said receiving means, said
repeater means including verification means for verifying that the
received identification signal is a valid identification signal before
said signal is retransmitted to said receiving means;
(c) receiving means positioned within said defined area for receiving said
identification signal;
(d) processing means coupled to said receiving means for noting the time of
receipt and content of the received identification signals, from which
time and content information a determination can be made as to the
presence or absence of the individual within the defined area during any
given time period; and
(e) tamper means included within said processing means for sensing one of a
plurality of tamper conditions associated with the use of said processing
means and for generating a tamper condition signal in the event that one
of said plurality of tamper conditions occurs.
20. A house arrest monitoring system comprising:
a plurality of electronic tags, each including means for periodically
transmitting an identification signal over a specified range;
a plurality of field monitoring devices, each of said field monitoring
devices including means for receiving the identification signals
transmitted by said tags when said tags are within the specified range of
said field monitoring devices;
at least one central processing unit coupled to said field monitoring
devices, said central processing unit including:
means for sorting, logging and processing the identification signals
received from each of said field monitoring devices,
means for generating reports that document the identification signals
received by said central processing unit, including the time at which any
given identification signal was received and the identity of the field
monitoring device from which it was received,
selection means for allowing an operator in contact with said central
processing unit to select a desired report to be generated by said central
processing unit;
monitoring means for monitoring the receipt of said identification signals
received from said field monitoring devices and for automatically
reporting any unusual patterns detected in the identification signals
received.
21. The house arrest monitoring system of claim 20 wherein said field
monitoring device holds the identification signals received from said tags
until contacted by said central processing unit, at which time said field
monitoring device sends the stored identification signals to said central
processing unit.
22. The house arrest monitoring system of claim 21 wherein said electronic
tags include means for sensing a tamper condition, and for including
information in said identification signal as to whether a tamper condition
has been detected by said tamper sensing means, said field monitoring
device further including means for automatically contacting said central
processing unit in the event that the identification signal received from
any one of said plurality of electronic tags indicates that a tamper
condition was sensed by the tamper sensing means within said tag.
23. The house arrest monitoring system of claim 22 wherein the monitoring
means within said central processing unit further includes means for
automatically generating a report in the event that an identification
signal received by one of said plurality of field monitoring devices
indicates a tamper condition was sensed by the tamper sensing means within
one of said plurality of electronic tags, said automatically generated
report including an identification of the electronic tag whereat the
tamper condition occurred.
24. The house arrest monitoring system of claim 20 wherein the central
processing unit is coupled to said plurality of field monitoring devices
by means of a communication link established over a telephone line.
25. The house arrest monitoring system of claim 24 wherein said central
processing unit includes means for contacting each of said field
monitoring devices in a systematic fashion, such as by polling each field
monitoring device in a prescribed order.
26. The house arrest monitoring system of claim 24 wherein said central
processing unit includes means for contacting each of said field
monitoring devices in a random fashion.
27. The house arrest monitoring system of claim 24 wherein said selection
means of said central processing unit further includes means for manually
selecting a given field monitoring device with which contact is to be
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Claims |
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Description |
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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 monitored for compliance with a sentence or
order to remain at a prescribed location.
To illustrate a potential application of a house arrest monitoring system
of the type disclosed herein, reference is made to a newspaper article
appearing in the Los Angeles Times on Wednesday, Sep. 12, 1985, Part I,
page 3. The article indicated that on Tuesday, Sept. 10, 1985, U.S.
District Judge Terry J. Hatter, Jr. sentenced David Alan Wayte to spend
"six months under house arrest at his grandmother's home for failing to
register for the military draft." While this was reported as "one of the
most unusual sentences in recent memory," it is believed to represent a
major trend for future sentencing of non-violent offenders. This is
particularly evident in view of the ever overcrowded prisons and jails
that exist in every jurisdiction across the United States and throughout
the world. House arrest thus represents a very significant and viable
alternative to conventional incarceration of convicted law breakers,
especially those found guilty of non-violent crimes.
While those sentenced to house arrest will generally recognize the need and
benefit of complying with the sentence imposed, there nonetheless remains
the need to monitor the presence or absence of such individuals to ensure
that the sentence imposed is being followed so that justice can be
satisfied. For example, in the instance cited above, the attorneys for the
convicted individual, David Wayte, wanted the judge to impose community
service work as punishment. While community service may be a very
appropriate sentence to impose in some instances, the judge felt that
because Mr. Wayte was already doing community service on a regular basis,
a sentence of house arrest should be imposed to punish Wayte by not
allowing him to perform such service. Hence, if Wayte were to violate his
sentence by leaving his grandmother's house without the knowledge of the
court, the purposes of Judge Hatter's sentence would be frustrated.
While monitoring the presence or absence of a single individual at a
prescribed location may seem like an easy task, it really is not,
especially if manpower and other resources are limited. Moreover, where
there are a large number of individuals who must be monitored, each at a
different "house-arrest" location, the problem becomes exceedingly more
complex, especially where some of the individuals may not want to fully
comply with the need to wear the tag at all times. Hence, there is a need
in the art for a system that can efficiently and accurately monitor the
presence or absence of a large number of individuals who have been
sentenced to remain at specific locations under house arrest.
Advantageously, such a system could also be used to monitor the presence
or absence of those individuals on parole, i.e., those individuals who are
more or less free to move about as they want during certain hours of the
day, but who must "report in" at specified locations at specified times.
The present invention meets this need by providing an electronic monitoring
system that inexpensively and accurately monitors the house-arrest
location of a large number of individuals at a wide variety of different
locations. Moreover, such monitoring is accomplished in a way that is not
readily noticeable to those persons with whom the monitored individuals
come in contact at the house-arrest location, and in a way that is
essentially tamper-proof and secure, with suitable alarm messages being
promptly given at a central monitoring location in the event that anything
out of the ordinary is sensed at a given house-arrest location.
Electronic monitoring systems used to determine and monitor the location of
individuals are known in the art. The concept of such electronic personnel
monitoring systems probably existed long before the technology was
available to realize them. Fictional accounts have long referred to the
concept of an electronic personnel monitoring system (e.g., the "Spider
Man " comic strip). Numerous press reports have also broadly discribed the
benefits of such systems, but have not disclosed the technology for how
such systems could be realized.
In Schwitzgebel, et. al., U.S. Pat. No. 3,478,344, there is disclosed a
prisoner monitoring system that keeps track of the location of prisoners
within a specified boundary. This is accomplished by a system that uses RF
transmitters, mounted on the wrist of the prisoner being monitored, and an
array of directional antennas that can determine the location of a
transmitter with respect to the antenna array. The wrist RF transmitter is
powered by a battery pack worn on the prisoner's belt. Two batteries are
employed so that the unit remains powered if one battery is removed. The
wrist band includes a conductive wire therein that, if broken or cut, is
used to signal that the wrist band has been improperly removed.
While the system disclosed in Schwitzgebel may have represented an
important advance in the art at the time it was made (1965), there are
many reasons why the system disclosed in Schwitzgebel may not provide a
viable house arrest system for use today. For example, the large battery
pack is unsightly and is cumbersome for the prisoner to wear. The antenna
array that must be placed around the premises is likewise unsightly and
draws attention to the fact that the location is being monitored.
Moreover, the conductive wire check of the wrist band could be easily
circumvented if a prisoner wanted to remove the device without being
detected. Further, external RF signals could easily interfere with the
intended RF signal, or external RF signals could be beamed into the
monitored area by an outside accomplice in order to "jam" the system.
In Mandel, U.S. Pat. No. 3,898,984, an ambulatory patient monitoring system
is disclosed. A telemetry system using a single RF frequency for each
individual to which the system is attached monitors critical body
functions. FM modulation is used. A transponder unit worn by the
individual is triggered by an interrogating signal, in response to which
interrogating signal selected information about the individual, as sensed
by special sensors on the individual, is transmitted to a receiver. In
this way, the receiver is able to monitor certain body functions of the
patient being monitored. However, location information about the patient
is not included in the transmitted information
In DePedro, U.S. Pat. No. 3,882,277, electrocardiograph information is
telemetered from a patient to a telephone transmission link system that
carries the informatiomn to a central monitoring location, Thus, a
combined telemetry and telephone transmission system is employed to
monitor physiological signals. However, as disclosed, such physiological
signals do not include the location of the patient being monitored.
In the UK Patent Application of Anders et. al., GB2141006A, a system is
disclosed that measures location, identification, or motion. The system
therein described uses "passive" tags that may be placed on movable
objects. The location of any of these movable objects may be ascertained
through a system that uses active transceivers to interrogate the passive
tags. In response to such interrogation, the passive tags transmit an
identification code. The location of the tag is sensed through the use of
multiple antennas spaced at predetermined intervals, or through
repeater-relay transceivers spaced at predetermined intervals, around the
area being monitored.
From the above it is seen that the prior art teaches electronic monitoring
systems that monitor the presence or absence of individuals from a
prescribed location and/or specified parameters of an individual at remote
locations. To accomplish such monitoring, it is known to use tags worn by
movable objects or individuals, RF telemetry to and from such tags,
repeaters, and telephone transmission links.
Despite these teachings of the art, however, no viable house arrest
monitoring system has yet been developed to applicants' knowledge. This is
because there are numerous features that must be present in a viable house
arrest monitoring system that are lacking in the teachings of the prior
art. For example, it is desirable to have the electronic tag or other
device that identifies the individual being monitored (usually some sort
of transponding device) to be worn at a location that is not readily
visible to the casual observer and at a location where it cannot be
removed by its wearer, but at a location where it will not unduly
interfere with the activities of its wearer. This requirement can be met
if the tag is worn on an ankle, thereby allowing the tag to be readily
concealed by the clothes (pants leg and/or sock) of its wearer. However,
such use causes the tag to be located very close to the ground, or floor
level. When the floor level comprises earth or concrete, as is often the
case, some significant transmission problems can result. This is because
the RF signal, by necessity a fairly weak signal that is generated for a
limited transmission range from a limited energy source, is either
absorbed in, or otherwise destructively reflected from the earth or
concrete surface. Further, concrete is often heavily laced with reinforced
steel, which also tends to interfere with reliable low-energy RF
transmissions. Moreover, the walls of the structure whereat the house
arrest is being performed may have wire mesh or other metal objects
therein that destructively interfere with the transmission of low-energy
RF signals.
Simply increasing the energy of the RF signals transmitted from the tag is
generally not a viable solution to this problem. In the first place, the
tag only has a limited energy source, and it is desirable to have this
energy source last for as long as possible. In fact, in accordance with
the teachings of the invention herein, the limited energy source (a
battery) should be permanently sealed in the tag so that the wearer of the
tag has no access thereto, In the second place, higher energy RF signals
create numerous other problems for those in the vicinity of the
transmission, and as such, must be carefully regulated by the FCC or other
regulatory agencies.
A further feature that desirably exists in a viable house arrest monitoring
system is that readily noticeable or visible antennas or antenna arrays
not be used. Such antennas immediately draw attention to the fact that a
house arrest situation exists. Accordingly, the antennas that are used
should be of the low profile variety that readily blend into the
surroundings of a typical house environment. Further, such antenna(s) and
related circuitry must be able to reliably pick up or sense the desired
signal and discriminate against destructive reflections or external
signals that may be present within the house-arrest structure .
Still a further feature that is of critical importance to the successful
use of a house arrest system is the integrity of the system. That is, all
components of the system at the house-arrest location must be able to
sense and signal the occurrence of any attempts to tamper therewith.
Further, while there is nothing that can absolutely prevent the
destruction of the system's components at the house arrest location, it is
desirable that such destruction or attempted destruction be promptly
communicated to a central processing location so that appropriate follow
up action can be performed. Most importantly, the electronic
identification (ID) tag that is worn by the person under house arrest must
not be removable. At a minimum, any attempts to remove the tag should be
detectable.
SUMMARY OF THE INVENTION
The present invention provides a reliable house arrest system that
automatically verifies the presence or absence of prisoners or other
personnel who are required to remain at a prescribed location or to report
in at the prescribed location at a certain time. Advantageously, the
prescribed location may be a conventional house, apartment, or other
building not intended for use as a prison or custodial facility.
Typically, the prescribed location will be a resindential house or
apartment where other individuals, such as the family of the individual
being monitored, may live and work with the individual under house arrest.
While such other family members will typically not be under house arrest,
the present invention advantageously contemplates that more than one
individual under house arrest may share the prescribed house-arrest
location, each being individually monitored.
More specifically, the present invention is directed to an identification
tag that is worn by the individual under house arrest. Typically, this tag
will be worn on the ankle of the individual, and its small size
advantageously allows the clothing of the individual to readily conceal
the fact that the tag is being worn. The identification tag periodically,
such as every 120 seconds, transmits an identification signal that
includes a prisoner identification code. This code uniquely identifies the
individual being monitored. Other information is also included in the
transmitted signal, such as information indicating that someone has
attempted to tamper with or remove the tag.
The identification signal generated by the tag is received by a Field
Monitoring Device (FMD) that is located within the house-arrest location.
A repeater may be selectively positioned around or within the house-arrest
facility in order to assure that the FMD always receives an identification
signal regardless of the location of the tag (that is, regardless of the
location of the individual wearing the tag) within the facility or
surrounding environs. The repeater receives the information signal from
the tag, holds it for a very short time, and retransmits it. The reception
patterns associated with the FMD and the tag for all possible locations of
the tag within the facility are checked at the tiem of installation. This
initial check identifies any "dead spots" or tag locations where tha tag's
identification signal is not properly received by the FMD. The repeater
can then be selectively positioned within the house-arrest facility in
order to eliminate the effect of such dead spots, thereby helping to
assure reliable communication between the tag and the FMD.
To further assure that the FMD reliably receives the information signal
transmitted from the tag, the FMD utilizes two receiving antennas that are
spaced apart a prescribed distance, which distance is a function of the
wavelengh of the transmitted signal. The distance between the antennas is
selected such that at least one of the antennas receives the information
signal in a non-nulled condition.
The FDM, in accordance with the preferred embodiment, includes a modem for
communicating with a central processing unit (CPU) via a telephone link.
Other types of communication links, such as microwave or satellite links,
could also be employed to couple the FMD to the CPU. Normally, the FMD's
will call the CPU whenever there is change associated with the
identification signal sensed (received) by the FMD. For example, if the
identification signals have been regularly received from the tag and the
signal stops being received, the FMD will call the CPU and log a "leave"
message. If no signals are being received by the FMD and signals appear,
the FMD will call the CPU and log and "enter" message. Such time logs
permit the system to determine the approximate time when an individual
being monitoring "checks out" or leaves and "check in" or enters the hose
arrest location. Additionally, the various FMD's call the CPU at
preestablished times stored by the FMD's and CPU's.
Advantageously, the FMD monitors the information signals received from each
tag (and FMD can receive signals from a plurality of tags) to monitor the
presence, absence and to determine if a tamper condition exists. A tamper
condition exists upon detection of an attempt to remove, alter, or
otherwise interfere with the normal operation of the system, including the
tag and the circuits of the FMD. In such situations, the FMD includes the
capability of calling up the CPU to alert it of such a tamper condition.
The CPB is located at a remote location fromthe house-arrest facility, and
includes the means for establishing a telephone or other communication
link with a large number of FMD's at a large number of house-arrest
locations. As indicated above, the FMD's normally call the CPU whenever a
leave, enter or tamper condition occurs. Additionally, the CPU will call
the various FMD's on a random basis in order to determine if all is well
at each location called. If the CPU is unable to establish a telephone
link with a given FMD after a prescribed number of attempts, which failure
might occur, for example, if the telephone lines or other communication
channels had been tampered with, the CPU generates an alarm condition so
that appropriate steps can be taken to find out what has happened.
Similarly, if the CPU receives a call from an FDM indicating that a tamper
condition has been detected, an alarm condition is generated.
Advantageously, the CPU is programmed to generate a wide variety of
reports that can be used by the monitoring personnel in order to quickly
and efficiently determine the status of all of the individuals being
monitored at the various house-arrest locations.
A feature of the present invention is that the house arrest system, in
addition to automatically verifying the presence or absence of prisoners,
also monitors the operating condition of the equipment used thereby
providing a means for allowing preventative maintenance to be performed in
a timely manner.
An additional feature of the present invention is that the identifying tag
worn by the prisoner or other individual being monitored is a
self-contained tag that is light-weight, tamper resistant, and that can be
worn on a limb of the individual in an unobtrusive manner. Further, the
tag is completely sealed, thereby protecting the electronic circuits
contained therein from exposure to damaging environments. The tag's
housing is made from a substance that is impervious to water and other
fluids to which the tag might be exposed. Further, the tag's housing is
made from a substance that is confortable and safe to wear when placed
against the skin of the individual who must wear it.
Most significantly, an important feature of the present invention is that
once tag is placed on the leg or other limb of the individual being
monitored, thereby placing the tag in proximity to the individual's skin,
any removal of the tag from the leg or other limb can be detected. This is
accomplished by combining a continuity check of a conductive strap or band
that holds the tag on the individual with a capacitive sending circuit
that senses when the tag is near human flesh and when it is not.
Because the tag is sealed, including the battery that is used to power the
circuits contained therein, an important feature of the tag is the ability
to preserve the life of the battery for as long as possible. Accordingly,
the operating circuits of the tag are configured such that they can
initially be totally shut down, as when the tag is first manufactured but
before it has been assigned to be worn by an individual under house
arrest, thereby preserving the life of the batteries contained therein.
However, the tag circuits can be selectively switched to operate in a test
mode when the device is frist used at a house-arrest location, thereby
allowing initial verification of the operation of both the tag and the
FMD, followed by a normal operating mode. Such modes of operation are
controlled, in the preferred embodiment, by the selective application of a
magnetic field.
A further feature of the present invention is that the system is able to
reliably operate even in very noisy RF environments. Special tramsmitting
circuitry housed in the tag, coupled with corresponding receiving
circuitry housed in the FMD, and additionally data decoding software,
allow the FMD to reliably discriminate between the intended RF signal
generated by the tag and noise.
Still another feature of the present invention is the ability of the FMD to
continue its monitoring operation of the tag or tags within the prescribed
house-arrest location even in the event of a line power failure. Such a
power failure might occur, | | |
