Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-07-30
2001-05-22
Hofsass, Jeffery (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572800, C340S572900, C340S573400
Reexamination Certificate
active
06236319
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns personal monitoring devices and more particularly such device utilizing a body worn transmitter which transmits an rf signal to a base unit at periodic intervals such that the presence of a person wearing the monitor within a predetermined range of the base unit can be verified. Such devices have come into relatively widespread use particularly in the context of the “tethering” of persons sentenced to home confinement. Such systems and devices have also been employed to monitor the presence of a person wearing a transmitter in an area which is forbidden to that person, to give warning or to enable notification of the authorities.
A recurrent problem with such devices is the possibility of the wearer substituting another transmitter by use of “code grabbing” equipment in which the code signal transmitted to the base unit is identified and such coded signal can then be reproduced with another transmitter device, allowing the tethered person to leave the premises without his or absence being detected by the base unit.
Another difficulty concerns the possibility that the tethered person will cut off the body worn device, typically held by a band which encircles the arm or leg of the tethered person. It is a simple matter to detect such severing of the band by causing this to interrupt the power supply circuit for the transmitter.
However, a variety of avoidance techniques have been devised, such as placing the band in salt water prior to severing, so that the circuit will not be broken when the band is severed since salt water is a relatively good electrical conductor.
Another drawback is that such systems are costly to administer for various reasons. The complexity and the cost of the equipment heretofore provided has been high. The fitting of large numbers of transmitters has also been a time consuming and expensive task for the enforcement authorities.
It is an object of the present invention to provide a body worn transmitter device which is relatively low in cost, yet reliable and resistant to attempts to defeat the system.
SUMMARY OF THE INVENTION
The present invention includes a transmitter adapted to be body worn by the monitored individual, having an encircling band custom fit to the limb of the individual involved by a quick and convenient procedure, and which is difficult to remove without detection.
The system comprises the body worn transmitter, a local base unit at a confinement location remote from a monitoring station, the monitoring station in communication with the base unit by a phone system (which could be conventional, cellular, etc.). The body worn transmitter sends a coded signal at short (variably set) intervals, i.e., one to five minutes, which are received by the base unit if within a variably set range from the base unit. The coded signal is changed with every transmission cycle to prevent code grabbing (i.e., a rolling code change). A crystal synchronized stored code selection is carried out in both the body worn transmitter and in the base unit (these are commercially available microprocessor-crystal devices suited to this purpose). Software synchronizes the body worn transmitter and base unit code generators at set up so that the same signal is generated by each.
If the properly coded body worn transmitter signal is not received at the prescribed times, the base unit may optionally be equipped with a transmitter having the ability to send a stronger signal to the out of range body worn transmitter or to a separate pager-alarm to trigger a vibration or other alarm on the body worn transmitter or the separate pager-alarm carried by the person, to warn that the wearer is out of range, allowing the person a chance to return to the confined location before the base unit reports a violation to the remote monitoring station.
If a properly coded signal is still not received after some additional brief time, the base unit sends a phone data report to the remote monitoring station, which alerts appropriate personnel of the situation.
The body worn transmitter is held with a limb encircling flexible strap or band which has an internal conductor forming part of a circuit which operates the battery powered transmitter. An activation key may be required to apply a coded start up signal when the strap is connected. The ohm resistance of the conductor at start up is detected and recorded in a microprocessor in the body worn transmitter, (after the band is cut to the correct size). If the band is cut, the transmitted signal stops. If immersion in a bucket of salt water is attempted to maintain an electrical connection, the difference in ohm resistance value will be detected, and prevent the coded signal will still not be transmitted.
The activation key is needed to be applied prior to reconnection if the band is disconnected.
The clock circuit which causes the periodic rf transmissions can alternatively be used which is shut off permanently whenever there is an interruption of a circuit of which the band forms a part.
A doubled antenna is embedded in the band and used to allow a variable range to be set by a change of program in the base unit microprocessor.
A hand held unit with stored code information for monitoring a number of people allows drive by checking of tethered individuals probationers, etc. This unit may have a signal strength indicator as a locator aid.
An alternative arrangement may be employed where a sophisticated band cut off feature is not deemed necessary, in which case a simplified software programming can simply prevent restarting of the transmitter upon any circuit interruption no matter how brief, in the circuit of which the conductor in the band forms apart.
In this case, a coded start up signal is required and will be employed when conducting the initial band fitting and when making any subsequent adjustments necessitating interruption of the transmitter circuit. A delay period may be programmed, allowing circuit interruptions for a brief time, i.e., 10 minutes, so that the fitting process may be completed.
The body worn transmitter, in addition to the rolling coded signal, also transmits an identifier signal to the base unit unique to that particular transmitter, and the base unit is preferably capable of a learning mode with a brief push button operation of the transmitter initially enabling the base unit to learn the identifier code of the particular transmitter being fit.
The coded start up signal can also be optionally applied by means of a transceiver installed in the body worn transmitter, in which the unique start up coded signal is transmitted to the body worn device, initiating the cyclical rf transmissions.
The body worn transmitter can also be employed as a monitor for detection of the presence of a person wearing the transmitter at some particular location forbidden to that person by a protective court order, using a receiver base unit at the forbidden location which will sound an alarm upon receiving a transmitted signal with the specific identifier signal unique to the transmitter worn by the person under court order.
The base unit in this instance can cause one or several prerecorded messages to be communicated via a modem and the phone system to various authorities. In addition, an alarm can be incorporated to sound or otherwise make a person or persons at the protected location aware of the presence of the person wearing the body worn transmitter. In this instance, transmission of a changing, i.e., rolling coded signal is not necessary, merely the unique identifier signal associated with the particular transmitter.
Also, the hand held unit can be employed by probation officers, etc., to monitor these locations to determine if the person is, in fact present at such locations. The hand held unit in this case can be provided with a number of stored identifier signals such that a number of several individuals may be monitored.
The system can also be used to monitor large numbers of people at a site (or items of equipment, livestock, inventory, etc.). In this case, a sca
Ghazarian John O.
Pitzer Beryl E.
Benefiel John R.
Hofsass Jeffery
Tang Son
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