Abstract: A device for detecting the specific gravity and level of liquid in a container comprising a light source, a photoelectric transducer positioned in light receiving relationship with respect to the light source, a float which has a predetermined specific gravity and is displaced depending upon the change in specific gravity and level of the liquid, and means operatively coupled to the float so as to permit or interrupt the light transmission from the light source to the photoelectric transducer.

Abstract: A device for indicating the specific gravity and/or the level of the electrolyte in a wet storage battery with the device having a magnetically actuated switch which is energized by a magnet on a floatation member which senses both specific gravity and the electrolyte level. An adjustable bias magnet is provided to modify the magnetic force applied by the first magnet on the switch to accommodate for manufacturing tolerances in the device and also to accommodate for dimensional differences in battery construction.

Abstract: A liquid level transducer actuates a relay to sound an alarm when there is a change in a liquid level in a tank. A bridge circuit is balanced at an existing liquid level to maintain the relay normally deenergized. A change in the liquid level unbalances the bridge circuit causing the relay to be energized. The system may be applied to stationary storage tanks or to vehicle fuel tanks to warn of theft of fuel. In a vehicle application an unauthorized movement of the vehicle would also cause sufficient shifting of the fuel in the tank to sound the horn and give warning.

Abstract: A brake fluid reservoir is provided having a flexible sealing diaphragm closing an open end of a chamber for brake fluid. A cover retains the diaphragm on the chamber carries stationary contacts, and a movable contact responsive to movement of a fluid level float, which movable contact, at a predetermined low level of fluid in the chamber, bridges the stationary contacts to complete a low-level warning circuit. Preferably two chambers are provided having a single diaphragm and cover, but a set of contacts for each chamber.