Abstract: A noise generator is created by having a high pressure gas applied to a Mach 2 nozzle which is combined in an adjustable nozzle assembly with a resonance tube of adjustable length with a closed end forming a Mach disk between them. The resultant compression and expansion shock wave oscillations exit the resonance tube and are propagated between reflecting domes which direct the generated noise around a test article in a housing which contains the generated noise. A muffler includes a water spray chamber and baffled bulkheads to dissipate the generated noise.

Abstract: A symmetry sensing safety circuit for automatically stopping electrical current flow through a thyristor to an electrical device which is supplied by a source of alternating current electrical energy.

Abstract: A fluid detector device and method capable of detecting the presence of a first fluid such as a gas, which may be mixed with a second fluid, in an external atmosphere where the first fluid is a hydrocarbon gas such as methane or the like, mixed with air, a semi permeable membrane, which extends across an opening of a detection chamber is utilized. Air and the gas have different rates of permeability across the membrane causing a volume change in the chamber. A volume sensitive device signals the presence of the gas. A displaceable element is shiftable in response to the volumetric change in the chamber, allowing the change without significant pressure changes. A capacitive plate can be integral with a displaceable element so that capacitance varies with the change in volume caused by the presence of the gas.

Abstract: An apparatus and method for automatically de-energizing electrically operable equipment in response to a lack of animal activity in a specified environment for predetermined time period. The apparatus of the present invention utilizes a circuit which is designed to detect activity which generates energy in a certain wavelength range and particularly, sonic energy in a certain environment and is responsive to the lack of activity within a certain predetermined time delay period or interval. Thus, if an activity which generates sonic energy is detected within a confined environment within the predetermined time interval, a signal is generated to energize or maintain energization of one or more electrical devices connected to the system of the invention. Contrariwise, if no sonic energy is detected within the predetermined time interval, there is a resultant de-energization of the electrically operable equipment. A control is provided to adjust the predetermined time delay period.