Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

Abstract: A cordless telephone system is provided which includes a base unit operatively coupled to a user's telephone lines and a relatively compact portable cordless handset. Both the base unit and the cordless handset include a radio transmitter and a receiver which form a full duplex two-way FM radio link wherein the transmitter of the base unit and the receiver of the cordless handset operate on a first non-CB frequency and the transmitter of the cordless handset and the receiver of the base unit operate on a second different and distinct non-CB frequency. Both the cordless handset and the base unit include signal-injecting circuitry whereby a portion of the transmitter signal is injected into the input of the receiver to provide the local oscillator function for that receiver without undesirable cross-talk between the transmitted and received signals.

Abstract: There is disclosed a processor controlled scanning radio receiver which employs a microprocessor controller to operate in various modes. One mode of operation is a search/recall mode wherein frequencies located during an automatic search operation are stored in a recirculating storage device for later user recall. The recirculating storage device is also employed to store frequencies or "birdies" to be locked out during a search operation. The channels to be scanned are stored in an electrically alterable read only memory in which the channels are arranged in five banks having ten channels per bank. A keyboard is included via which a user may select or deselect any one or more banks for the scanning operation.

Abstract: There is disclosed a scanning radio receiver intended for use on the frequencies assigned to the Public Safety Radio Services and which is also operable for reception in the aircraft band from 118 MHz to 136 MHz. A voltage controlled oscillator is provided which is operable at frequencies up to nearly 175 MHz for producing an output signal for direct mixing with received signals in the low and high VHF bands as well as in the aircraft band and for tripling to provide a first local oscillator signal for UHF operation up to 512 MHz. A divider circuit is provided for direct countdown from the frequency of the voltage controlled oscillator to produce a low frequency signal for comparison with a fixed frequency signal of 5 KHz, or in the case of UHF operation, 4.167 KHz. The countdown circuitry along with the phase detector and divider circuits for producing the reference are all mounted on a single integrated circuit chip.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: A mobile citizens band radio transceiver having the circuitry partitioned so as to permit the chassis housing the receiver circuitry, transmitter circuitry and frequency synthesizer circuitry to be installed in a remote location in a motor vehicle such as behind the dashboard, under the seat or in the trunk thereof, or the like, so as to reduce the possibility of theft and/or the likelihood that the chassis could cause injury to the occupants of the vehicle in the event of an accident or sudden stop by efficiently housing all of the control circuitry in a combination microphone and control unit adapted to be held in the hand of the operator of the vehicle and operated by the same hand which is holding the combination unit. By having all of the controls located in the microphone, a jack plug arrangement or the like can be utilized so that the microphone can be easily removed when the operator is not in the vehicle so that no sign of the presence of the CB radio will be visible to a potential thief.

Abstract: A wireless seed detecting and monitoring apparatus includes one or more transmitter units mounted at the seed planter and a receiver unit mounted in a monitor console located at a remote location. Seeds being planted produce a signal which modulates an r-f transmitted signal during the planting operation. A receiver is responsive to the r-f transmitted signal and detects the modulated signal information corresponding to seeds being planted. This detected signal is then delivered to monitoring circuitry to indicate the operation of the seed planter.

Abstract: There is disclosed a liquid velocity measuring apparatus comprising an actuable generator for providing a relatively high frequency signal to a transmitting transducer for directing an ultrasonic wave into a conduit through which liquid is directed. A receiver transducer is disposed to receive the acoustical wave as reflected from the liquid, and to provide an output signal to be amplified and demodulated to provide a train of high frequency pulses, the frequency of which is indicative of the velocity of the liquid directed through the conduit. The train of pulses is applied to a counter and a decoder for respectively counting and decoding the pulses to provide a signal to a display whereby a digital indication of the liquid velocity is given.

Abstract: There is disclosed a liquid velocity measuring apparatus comprising an actuable generator for providing a relatively high frequency signal to a transmitting transducer for directing an ultrasonic wave into a conduit through which liquid is directed. A receiver transducer is disposed to receive the acoustical wave as reflected from the liquid, and to provide an output signal to be amplified and demodulated to provide a train of high frequency pulses, the frequency of which is indicative of the velocity of the liquid directed through the conduit. The train of pulses is applied to a counter and a decoder for respectivey counting and decoding the pulses to provide a signal to a display whereby a digital indication of the liquid velocity is given.

Abstract: There is disclosed a signal-seeking superheterodyne radio receiver for use on the public service radio frequencies capable of scanning among a plurality of channels and using frequency synthesizing apparatus to generate the required local oscillator signals. An electrically programmable, nonvolatile memory is included for controlling the frequency to which the receiver is tuned when it is operative on any given channel. The receiver includes a plurality of manually operated switches for selectively locking out individual ones of the receiver channels and inhibiting the reception of signals at the frequencies corresponding to the locked out channels. It further includes programming circuitry for altering the information contained in the memory and, thus, the frequency corresponding to any individual channel. The programming circuitry uses the channel lockout switches for data entry and includes apparatus for defeating the channel lockout function when data is being prepared and entered into the memory.

Abstract: A signal-seeking scanning radio receiver employing a selective rescan delay circuit for delaying automatic resumption of multi-channel scanning for a period of time following termination of a signal on a tuned channel in response to an auxiliary output signal from a memory programmed to provide auxiliary output signals only for certain preselected channels tuned to a predetermined frequency on which two-way communications are anticipated without delaying automatic scan resumption for channels on which only one-way communications are anticipated.

Abstract: There is disclosed a signal-seeking, scanning superheterodyne radio receiver using frequency synthesizing apparatus to generate the required local oscillator signals and capable of receiving signals on all four bands comprising the public service radio frequencies. The frequency synthesizing apparatus includes circuitry for selectively altering the frequencies of the reference oscillator signal and the offset oscillator signal. Alteration of the reference oscillator signal frequency permits economical use of the same frequency synthesizing apparatus in different bands wherein the spacing between adjacent frequencies is different, whereas alteration of the offset oscillator signal frequency permits the generation of local oscillator signals which fall between multiples of the reference signal frequency.