Abstract: A liquid sensing switch comprising an upper sensor plate linked to electronics, a lower sensor plate linked to the electronics, and a ground linked to the electronics, wherein a pump is activated when a liquid level rises above a position of the lower sensor plate and above a position of the upper sensor plate, causing a current to pass between the two sensor plates.

Abstract: A system includes a pump, a liquid sensing switch linked to the pump and suspended in an area, the liquid sensing switch including a large surface area upper bare uninsulated stainless steel sensor plate linked to electronics, a large surface area lower bare uninsulated stainless steel sensor plate linked to the electronics, and a large surface area ground linked to the electronics, the pump activated when a liquid level in the area rises above a position of the lower bare uninsulated stainless steel sensor plate and a position of the upper bare uninsulated stainless steel lower sensor plate, causing a current to pass between the two sensor plates.

Abstract: A liquid sensing switch comprising an upper sensor plate linked to electronics, a lower sensor plate linked to the electronics, and a ground linked to the electronics, wherein a pump is activated when a liquid level rises above a position of the lower sensor plate and above a position of the upper sensor plate, causing a current to pass between the two sensor plates.

Abstract: A detector for detecting a change in a fluid level and generating a digital signal uses a light source and a photodetector mounted diametrically on a tube in a predetermined location where a change in fluid level is to be detected. The circuit provides two stable output states or levels, one which corresponds to fluid not being in the tube between the light source such as an LED light and the photodetector and the other level when fluid is in the tube. In a particular application, the invention is utilized to monitor fluid level in a predetermined location of a manometer to shut off a radon remedial system and provide audio/and or visual alarms when there is a fluid level change which indicates that the radon remedial system is not operating effectively.

Abstract: A detector for detecting a change in a fluid level and generating a digital signal uses a light source and a photodetector mounted diametrically on a tube in a predetermined location where a change in fluid level is to be detected. The circuit provides two stable output states or levels, one which corresponds to fluid not being in the tube between the light source such as an LED light and the photodetector and the other level when fluid is in the tube. In a particular application, the invention is utilized to monitor fluid level in a predetermined location of a manometer to shut off a radon remedial system and provide audio/and or visual alarms when there is a fluid level change which indicates that the radon remedial system is not operating effectively.

Abstract: A liquid level detecting system for detecting a conducting liquid level in a non conductive container which utilizes a grounding rod mounted in a lower portion of the container and a conductive sensing rod mounted at a position above the grounding rod. An oscillator is provided having a frequency in the range of about 600 hertz to about 100 kilohertz. The output of the oscillator is applied to the sensing rod through a high impedance circuit and a high pass filter. In another embodiment, the high pass filter may have the higher end frequencies attenuated to produce a band pass filter which selectively passes the frequency of the oscillator. The voltage drop across the circuit which includes the conductive sensing rod to ground is detected by a voltage peak detector and a threshold detector to produce an output which detects the drops in voltage when the conductive fluid level in the tank rises so that both the sensing rod and the grounding rod are covered, completing the circuit.

Abstract: A liquid level detecting system which utilizes audio frequency with components having sizes and values usually associated with RF frequencies, thereby providing the reliability and low cost of audio components with the small size typically associated with RF systems. A conductive element is mounted within a container, the conductive element is provided with an insulative coating. A large change in capacitance and capacitance reactance is produced when the insulated conductive element is immersed in a conductive liquid. The change in output of the audio oscillator, passed through the low pass network, which includes the capacitance of the conductive element is fed to an active detector. In one application, the detector is utilized to sense the level of water in a fuel/water separator and, in a second application, a pair of liquid level detectors are utilized to control the operation of a bilge pump.

Abstract: A torque limiting device for preventing the transmission of torque from a drive source to a torque responsive element when a predetermined torque limit has been reached. The device operates by transmitting torque between two axial members having a plurality of balls therebetween with the balls engaged within precisely shaped sockets contained within each axial member. As excess torque occurs, the plurality of balls cause one member to axially displace with respect to the other member and engage a plurality of discs which lock both members, thereby preventing torque transmission.

Abstract: An amplitude modulated transmitter is disclosed for use in the frequency range generally below 50 mega-hertz. The transmitter is provided with a series diode modulator which is provided with a corrected modulating signal which biases the diode in proportion to the modulating signal. The modulating signal is derived from comparison in a difference amplifier between the desired audio input signal and a signal derived from the output of the output amplifier by means of a directional coupler. The directional coupler samples the magnitude and phase of the current and voltage at the output and feeds a signal proportional to the inciden as contrasted to any reflected component, of the output signal.