Abstract: A body coupled antenna system usable in a personal locator unit includes an antenna element for connection to an RF circuit; a coupling plate for conductively coupling to an adjacent body for broadening the tuning frequency and reducing the loading sensitivity; a first capacitance interconnected between the coupling plate and the antenna element; and a second capacitance interconnected between the coupling plate and the RF circuit; the first and second capacitances being set to restore a predetermined matching impedance level while maintaining the broadened tuning frequency.

Abstract: A SAW resonator filter including a SAW resonator, and a first inductive reactance in parallel with the SAW resonator for shifting the null points below and above the center frequency for establishing substantially symmetrical attenuation about the center frequency.

Abstract: An improved fast settling bit slicing comparator circuit includes a comparator having a non-inverting and inverting input; the non-inverting input receiving an input signal; a filter circuit for receiving the input signal and being connected with the inverting input of the comparator; a positive feedback circuit interconnected between the output of the comparator and the non-inverting input of the comparator for introducing a predetermined hysteresis offset; the filter circuit including a filter resistance and filter capacitance having a reduced time constant sufficient to compensate for at least a portion of the hysteresis offset. Additionally, the positive feedback circuit may be interconnected with the inverting input of the comparator through the filter circuit for gradually reducing the effect of the hysteresis offset by reducing the differential voltage between the inverting and non-inverting inputs.

Abstract: A method of operating a vehicle locating unit wherein an activation signal is received when the vehicle is stolen and in response to the activation signal, a signal indicating the vehicle has been stolen is transmitted. The receiver is energized for an actual duration Non periodically to listen for the activation and other signals. Estimating how long the receiver has been on includes incrementing a counter at a count resolution where Non is typically at least sometimes less than the count resolution. Estimating the total amount of time the receiver was energized is based on a measured on time after it converges with the actual on time.

Abstract: A notched SAW image frequency rejection filter system includes a SAW filter having an input, an output and a ground output and an impedance matching network including a first matching inductance connected to the SAW filter output and a second matching inductance connected to the ground output of the SAW filter; the SAW filter having an inherent internal capacitance that produces a predetermined capacitive leakage current at the image frequency; an inherent internal inductance that produces an inductance leakage current at the image frequency; and a boosted inherent parasitic ground inductance at the ground output of the SAW filter for generating a voltage across the second matching inductance to produce a compensation current which is substantially opposite in phase and substantially matched in magnitude with the capacitive leakage current for reducing the capacitive leakage current and increasing the image frequency rejection.

Abstract: A combined proximity monitoring and locating system including a wearable unit, a proximity detector, and a control subsystem. The proximity detector includes a receiver for receiving the wearable unit transmitter signal, a processing subsystem configured to signal an alert if the wearable unit transmitter signal strength is below a pre-established minimum, and a tracking subsystem configured to assist in locating the wearable unit based on the signal strength of the wearable unit transmitter signal. A control subsystem is responsive to an indication that the alert has been signaled. The control subsystem includes an RF transmitter configured to transmit a transponder activation signal, and an RF antenna network for relaying the transponder activation signal to a receiver of the portable unit to activate the transponder thereof. A tracking unit includes a receiver configured to receive the transponder signal of the wearable unit to locate the wearable unit.

Abstract: Dual table temperature compensation for a voltage controlled crystal oscillator is achieved by sensing the temperature of the voltage controlled crystal oscillator (VCXO), retrieving from a first table the frequency error with variations in the temperature sensed, retrieving from a second table the oscillator control voltage corresponding to the frequency error from the first table and applying the oscillator control voltage to the VCXO.

Abstract: A method of expanding the activation and tracking capability of a limited number of stolen vehicle recovery dedicated radio-frequency networks activated from a control center upon notification of the theft of the vehicle includes supplementarily using more numerous widely geographically provided cellular-telephone frequency band networks to respond to the control center to indicate rough location of the stolen vehicle, while the recovery networks provide fine tracking of the vehicle for recovery.

Abstract: An asset location, tracking, and recovery system and method includes a network of VHF towers and a control center receiving signals from and transmitting signals to the VHF towers. Primary locating units each include a transmitter, a receiver, and a transponder activated when a signal is transmitted by the control center via the VHF towers to the receiver. Auxiliary locating units include at least a transmitter emitting a signal received by at least one primary locating unit receiver which relays that signal to the control center via the VHF towers from the primary locating unit transmitter.

Abstract: An improved motion sensing and alarm technique and apparatus for monitoring unauthorized movement of vehicles or the like and notifying the owner thereof, wherein the motion sensors in the vehicle are microprocessor controlled to be automatically armed when the owner is not in the vicinity of the vehicle, but disarmed or de-activated in the presence of the owner and the owner's radio-coded identification transmitter associated with the owner's key fob, and with energy saving features as well.

Abstract: A method of checking messages from a network of communication sources includes initially testing the signal strength of a plurality of communication sources, storing the identity of the communication sources with the two strongest signals, and alternatively entering a sleep mode and a wake-up mode, the wake-up mode synchronized to the communication source with the strongest signal. The method further includes testing the signal strength of one additional communication source, switching synchronization to the additional communication source if said source presents a signal stronger than the signal of a stored communication source with the strongest signal, and replacing the identity of any stored communication source if an additional communication sources tested in sequence presents a signal stronger than the signal of said stored communication source.

Abstract: A recovery system with repeating communication capabilities. The system includes a station configured to send an activation message, at least a first “primary” remote transmitting unit responsive to the station and configured to transmit the activation message and at least a one “secondary” remote transmitting unit. That unit includes a receiver which receives the activation message, a transmitter for transmitting the activation message, and a controller responsive to the receiver and controlling the transmitter. The controller is programmed to transmit the activation message and then automatically stop transmission of the activation message after a predetermined time period unless the activation message is again received.

Abstract: A vehicle locating unit with improved power management. A receiver receives a signal from a network of communication sources. A signal strength monitoring subsystem determines which of the communication sources are transmitting the strongest signals. A power management subsystem is responsive to the signal strength monitoring subsystem and is configured to alternatively enter sleep and wake-up modes, synchronize the wake-up mode to the communication source transmitting the strongest signal, and test the signal strength of at least one additional communication source according to a predefined sequence.

Abstract: A system and technique for improving the speed and ease of missing vehicle location and recovery by vehicle-carried transponder periodic coded replies to radio interrogation by a network of (VHF) transmitting towers, by integrating a concealed GPS location receiver with the transponder and providing the GPS-obtained coordinate information through the VHF network to enable a preliminary initial recovery location from which to home-in for recovery by subsequent direction-finding from the periodic transponder responses. Other location-on-demand services are also readily operable through the use of this VHF network, including providing said GPS coordinate or location information on the Internet.

Abstract: Extending the activation and tracking capability of stolen vehicle recovery dedicated radio-frequency networks by the supplementary use of widely geographically provided cellular telephone-frequency band networks.

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

Abstract: A novel method of and system for enabling the use of one portable cellular phone only, in voice communication with a cellular network control center for voice-requesting position or location data services, and, with the aid of a vehicle GPS-transponder activated in response to signaling from the control center over cellular network channel control paths, to receive and process at the vehicle GPS location data from satellites, and to transmit the data over the said channel control paths to the control center, for then sending therefrom to the user of the portable cellular phone.