Abstract: A fluid level sensor for determining a fluid level within a container, includes a transducer for generating sonic or ultrasonic waves and a wave guide. The wave guide has a first end operatively coupled to the transducer and a second end for immersion into the fluid, the second end spaced a predetermined distance from the first end, wherein a gap is formed between the first end and the second end. The sensor can be used to measure a fluid level using both an impedance mismatch signal and a fluid conductance signal.

Abstract: A fluid level sensor for determining a fluid level within a container, includes a transducer for generating sonic or ultrasonic waves and a wave guide. The wave guide has a first end operatively coupled to the transducer and a second end for immersion into the fluid, the second end spaced a predetermined distance from the first end, wherein a gap is formed between the first end and the second end. The sensor can be used to measure a fluid level using both an impedance mismatch signal and a fluid conductance signal.

Abstract: A multi-frequency ultrasonic liquid level gauging system includes a storage apparatus for storing a volume of liquid and a plurality of ultrasonic transducers. Each transducer introduces a distinct ultrasonic signal into storage apparatus and receives a reflected signal back. A circuit drives and receives signals from the ultrasonic transducers. A processor calculates the liquid level at each of the locations of ultrasonic transducers based on the reflected signal received from each transducer. Transducers are connected in parallel, thereby allowing circuit to communicate to the transducers through a single conductive path. A method of measuring a liquid level in storage apparatus includes emitting a single drive signal to a plurality of ultrasonic signal sources, wherein each source is operable to transmit ultrasonic signals having unique frequencies. The ultrasonic signals are transmitted through liquid and each is reflected at the liquid surface.

Abstract: A system for indicating the mass of fuel in several fuel tanks of an aircraft has a capacitive depth sensor and a permittivity cell located in each tank. Signals from the sensors and cells are supplied to a computing unit which computes the volume of fuel in each tank and its approximate density. The system has a densitometer and another permittivity cell which receive a sample of all the fuel supplied to the tanks, and supply output signals to the computing unit. The computing unit derives a correction factor by comparing an approximate value of density derived from the other permittivity cell with a more accurate measure of density derived from the densitometer. The correction factor is used to correct the approximate values of density derived from the permittivity cell in each tank.

Abstract: A recording and reproducing machine in which electrical signals are recorded on a recording medium while the medium is driven forwardly along a predetermined path. Recording and reproducing means are switched between record and reproducing modes. Detecting means are associated with means for switching electrical connections in the machine between record and reproducing modes. The detecting means assume a predetermined condition when the end of the last recorded signal on the recording medium is adjacent to the recording and reproducing means. The driving means can then be operated to drive the medium forwardly only if the switching means are in the record mode.

Abstract: A remotely controllable electrical equipment is fitted with a decoder device associated with which is an unlocking circuit. Access to the electrical equipment is obtained by transmitting an access signal from a remote coder device. The access signal is made up of three groups of pulsed electrical signals, each group comprising two pulses of frequencies different from each other. The first group of pulses unlocks the unlocking circuit for a first predetermined interval of time. If the second group of pulses arrives within this first predetermined interval of time the unlocking circuit is unlocked for a second predetermined interval of time. If the third group of pulses arrives in the second predetermined interval of time an output signal is applied to the associated electrical equipment. Control signals for operating the equipment can then be transmitted from the coder device to the equipment via the decoder device.