A system and method for providing computerized, knowledge-based medical diagnostic and treatment advice. The medical advice is provided to the general public over networks, such as a telephone network or a computer network. The invention also includes a stand-alone embodiment that may utilize occasional connectivity to a central computer by use of a network, such as the Internet. New authoring languages, interactive voice response and speech recognition are used to enable expert and general practitioner knowledge to be encoded for access by the public. “Meta” functions for time-density analysis of a number of factors regarding the number of medical complaints per unit of time are an integral part of the system. A re-enter feature monitors the user's changing condition over time. A symptom severity analysis helps to respond to the changing conditions. System sensitivity factors may be changed at a global level or other levels to adjust the system advice as necessary.

Computerized medical diagnostic and treatment advice system including network access

A method for a frequency synthesizer with adaptive loop bandwidth is disclosed, which is adjusted by the improved frequency synthesizer includes a phase-locked loop and a phase-locked loop adjustment circuit. The phase-locked loop has loop characteristics including a loop bandwidth, a natural frequency, a damping factor, and the like. The phase-locked loop adjustment circuit is adjusted in response to a change in output frequency.

Frequency synthesizer with adaptive loop bandwidth

An improved voltage reference circuit is shown for use in analog integrated circuits including A/D and D/A converters. The voltage reference circuit comprises an operational amplifier having an non-inverting terminal connected to a capacitor. The inverting terminal of the op amp is connected to the op amp output terminal. The output terminal provides a constant reference voltage which is a function of the voltage charged in the capacitor. The capacitor includes a floating gate, an isolating layer, and a controlling gate which is used to charge (program) the capacitor to a fixed voltage. The capacitor structure is such that its charge is maintained constant over time independent of any temperature change. As a result, the voltage reference circuit prevents fluctuations in the output reference voltage throughout its operating period.

Voltage regulator for generating a constant reference voltage which does not change over time or with change in temperature

A system and method for synchronizing a parking meter clock is provided. The system includes a parking meter having a clock and an antenna coupled to the parking meter for receiving a wireless broadcast data including a time data. The parking meter further provided with a receiver and an interface. The receiver communicates with the antenna to demodulate the wireless broadcast data received by the antenna and the interface communicates with the receiver to communicate the wireless broadcast data to synchronize the clock on the parking meter. A method of synchronizing a clock on one or more parking meters is also provided that includes receiving a wireless broadcast data including a time-of-day data. The method further includes updating the clock on the parking meter based on the wirelessly broadcast data. In one aspect, the time-of-day data is based on an atomic clock.

System and method for synchronizing a parking meter clock

A digital to analog converter which includes a delta-sigma modulator for transforming the lower n bits of an input digital signal of N bits by delta-sigma modulation; first and second signal output devices for outputting first and second signals which are used for selecting current cells of a current cell array according to the higher bits and the higher bits+one LSB of the input digital signal, and a selector for selecting either of the first and second signals in accordance with the change of the output of the delta-sigma modulator. A filter is provided for smoothing the total of the currents output from the current cells which are in the output state corresponding to the first or second signal selected by the signal selector.

Digital to analog converter and frequency synthesizer using the converter

A voltage divider circuit having divider resistors which are not precision resistors. A first oscillating signal is input into a first resistor and the complement of the first oscillating signal is input into a second resistor. The two resistors are connected together and to a filter. Other means, such as transistors, may be utilized in lieu of the resistors. The output at the filter is the D.C. level of the first oscillating signal which is one-half or other designated ratio of the input voltage. Buffers may be incorporated in the invention.

Precision voltage divider

An improved synchronous tracking AM receiver having low power requirements and a small size. The synchronous tracking AM receiver provides signal tracking capability and sensitivity approaching a conventional superhetrodyne receiver. The synchronous tracking AM receiver includes an RF amplifier synchronous input section which couples input signals to a synchronization filter circuit, including a modified Colpitts oscillator. The Colpitts oscillator recycles the signal to generate a high Q output signal. The output signal of the synchronization circuit is coupled to a low pass filter, then amplified by a low frequency amplifier and triggered to produce a digital output signal.

Synchronous tracking am receiver.

A precision ratioed digital-to-analog data converter. A first latch stores a first digital word having a first numerical value and a second latch stores a second digital word having a second numerical value. A down counter alternately receives data from the first and second latches and is connected to a flip flop device to produce a waveform signal having first and second pulse components of opposite polarity. The first and second pulse components have a duration proportional to the first and second digital words. The output waveform is then inverted through an inverter comprising matched P and N channel MOSFETS. The inverted waveform is then presented to an RC integrator circuit which produces a DC signal. The DC signal is passed through a buffer amplifier connected in a voltage follower configuration.

Digital-to-analog converter

An enhancement for a phase locked loop, where the enhanced phase locked loop includes a phase detector having an output and first and second inputs, the enhancement circuits of the invention, a loop filter and a voltage controlled oscillator having a control signal input and a signal output connected to the second input of the phase detector. One embodiment of the enhancement comprises a first amplifier for amplifying the output signal from the phase detector, a matched quad diode array having first and second nodes, a second amplifier and first, second and third resistors each having first and second terminals. The first terminal of the first resistor is connected to the first terminal of the third resistor and also connected in common to the first amplifier output. The second terminal of the third resistor is connected to the second node of the quad diode array, the first terminals of the first and third resistors and the inverting input of the second amplifier. The second amplifier's output is connected to the second terminal of the second resistor and further connected to the loop filter input. The loop fitler is, in turn, connected to the control signal input to complete the circuit for the enhanced phase locked loop. In operation, the control signal responds to variations in forward conductivity of the matched diode array which, in turn, responds to the voltage swings of the amplified phase detector output.

Enhanced phase detector

A phase locked loop including a digital control is provided. A phase detector having first and second inputs and an output connected to a loop filter which responds to the digital control so as to modify the output. The loop filter further comprises apparatus for integrating and a first apparatus for amplifying the modified phase detector output, each of which provides an output signal. An apparatus for digitally controlling the loop filter parameters responds to externally generated digital commands so as to vary loop parameters. A first apparatus for generating a voltage controlled oscillation signal is connected to the first input, where the voltage controlled oscillation apparatus includes a voltage control signal input. Further included is a second apparatus for generating a voltage control signal responsive to the sum of the output signals of the integrating apparatus and first amplifying apparatus, where the second generating apparatus transmits the voltage control signal to the voltage control signal input of the first generating apparatus so as to control the oscillation frequency. In one embodiment of the invention, the digital control apparatus comprises a digital-to-analog converter which responds to externally generated digital signals to provide a variable resistance so as to correspondingly change the natural frequency and damping of the phase locked loop in response to the external digital signals.

Michael A. Wyatt

Papers

Precision voltage divider

Synchronous tracking am receiver.

Digital-to-analog converter

Enhanced phase detector

Digital control for analog phase locked loop