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 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.