Abstract: Aqueous film-forming foam (AFFF) concentrates for fighting polar and non-polar fuel and solvent fires, comprising hydrocarbon solvents, hydrocarbon surfactants, fluorosurfactants, high molecular weight polysaccharides, alginates, salts of aryl or alkylaryl sulfonates and water, and method for modifying the viscosity of the AFFF concentrates.

Abstract: A bi-stable electromagnet operator having an armature plate which is held in a first position by a permanent magnet and in a second position by a spring. An electromagnet is provided to enable the armature plate to move from the first position to the second position. The magnet has high coercivity and therefore the permanent magnet and core of the electromagnet can be in close magnetic contact both when the armature is in the first position and in the second position. The high coercivity of the permanent magnet provides for sufficient flux flow to maintain magnetization when the armature plate is in the second position away from the permanent magnet. Typically, the permanent magnet comprises neodymium.

Abstract: A pressure equalizing valve comprises a valve body with a longitudinally disposed bore therein, and a spool disposed in the bore for longitudinal movement to regulate fluid communication from an inlet port to outlet ports in response to a pressure differential between first and second sense ports disposed on first and second end faces of the valve body.

Abstract: In a microprocessor controlled fire alarm system, a chain of continuous pulses is generated by the microprocessor. The chain of continuous pulses is monitored, and if there is an interruption in the chain of continuous pulses a signal is generated to automatically reset the microprocessor.