A digital vehicle detection system is provided which responds to changes in the inductance of a wire loop embedded in the roadway to sense the presence of a vehicle. The loop and associated lead-in connections are used as the frequency-determining network of a Class-C oscillator, and digital circuitry is used to measure the frequency of the oscillator. An automatic tuning circuit is included which generates a reference time frame for the frequency measurement, and vehicle detection is sensed whe...

1. A torpedo detecting device of the character disclosed comprising, in cination, a plurality of microphone units, means including orientation means for providing each of said units with a vertically arranged substantially dumbbell-shaped response pattern to a sound signal received thereby from a torpedo moving transversely with respect thereto, and coupling means for spacing said units with respect to each other in such a manner as to provide an overlapping of the response patterns of adjacent ...

A moisture detector comprising a container surrounding a detection area with a channel leading out of the container, a member connected in the channel with a portion of the member inside the container and a portion of the member outside of the container, and a switch connected adjacent the distal end of the portion of the member lying inside the container. The member absorbs moisture relative to the moisture in the surrounding soil. The change in weight of the member changes the position of the ...

A method of detecting the presence of a foreign gas in a gaseous medium of known combustion properties uses the fact that the percentage lower or upper explosive limits (LEL or UEL) of mixtures of any flammable gas in any other gas all have approximately the same varying relationship to the percentage LEL or UEL of the mixture as a whole when a known percentage of a reference gas of known combustion properties is added to the mixture. The method comprises the steps of mixing a sample of a possib...

To select a blend of strains not susceptible to the current bacteriophage in the cheesemaking plant the cheesemaker inoculates each of the test tubes in the kit with filtered when obtained from current production. Each tube contains a genetically distinct starter culture strain or a culture blend in a sterile milk medium and contains a dye which will change color in the desired pH range. After incubation for ten hours the cultures resistant to the prevailing phage will exhibit the desired color ...

1. In a torpedo detecting device of the class disclosed, the combination of n elongated hose-like member having a towing device secured to one end thereof whereby the member is adapted to be towed through a body of water, and means in said member and remote from said towing device for disconnecting said member at a predetermined point in closely spaced adjacency from the towing device comprising a helical coil of explosive fuse cord disposed only at said point and capable of sufficient explosive...

A method and apparatus for detecting and monitoring radon gas and its alpha-emitting daughter products. A sheet of track-registration material is exposed in an area to be monitored, the material having the property of forming damage tracks along paths traversed by alpha particles. After exposure, the material is etched with a reagent to enlarge the tracks, making them visible so they can be counted. The number of tracks formed during the exposure period is a measure of the amount of radon and ra...

An optical fire detector in which a red-responsive cell and a blue-responsive cell are connected into a voltage divider circuit, and a third cell non-responsive to a specific frequency band is connected between the junction of the first two cells and the input of an amplifier of an alarm circuit.

A signal detector comprising in combination a thin photosensitive element sandwiched between partially transparent electrodes; amplifier means connected to the detection element; and utilization means connected to the amplifier.

The presence of nitrogen containing compounds is detected by sampling vapor in the vicinity of the suspected compounds, reacting the vapor under conditions to convert the compound to nitric oxide. The nitric oxide is reacted with atomic oxygen with the chemiluminescent emission of light. This light is detected to determine the presence of the suspected compound.