Abstract: An apparatus and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured. The volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller. Moreover, for calibrating the apparatus, a return air sensor is calibrated to the outside air and a mixed air sensor is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.

Abstract: An information display system has a display screen which is substantially transparent to a selected band of wavelengths of light and can be mounted on a window. A projector projects an image of light of the wavelengths to which the display screen responds onto the screen to reflect or transmit the selected wavelengths of light from the screen. The screen is formed as a holographic optical element which reflects the light such that an observer is able to see the projected image from the display screen only if his eyes are within a predetermined area, while observers outside of the area see only a substantially transparent display screen on the window.

Abstract: Method and apparatus for implementing a digital filter employing coefficients expressed as sums of 2 to an integer power. Coefficients expressed as sums of powers of 2 may be algebraically manipulated such that higher order terms are replaced by an equivalent group of lower order terms. In the context of a shift-and-add algorithm, the lower order terms require fewer shifting operations and less total hardware to effect multiplication than the corresponding higher order terms.

Abstract: A noise suppression system for use on internal combustion engines and small enough for use in automotive applications is disclosed. A cancellation noise generator and actuator speakers produce a noise to combine with and cancel the engine noise carried in exhaust gases in a mixing chamber. The resultant noise leaving the mixing chamber is measured by a circular tubular microphone array to control the noise generator.

Abstract: The present invention relates to a tool and method for installing a roof fastener for securing insulation or waterproof membrane to a rooftop.

Abstract: A tang extends from a cover pivotally attached to a mounting plate of an electrical outlet to interconnect with and lockingly engage a lip extending from the mounting plate. A key, insertable through a keyway in the bottom side of the cover, is used to force the tang upwardly out of engagement with the lip and to unlock the cover from the mounting plate. Subsequent downward pivotal movement of the cover toward the mounting plate will relock the cover.

Abstract: A bullet is provided which is substantially 100% pure fluorocarbon resin. In the preferred embodiment a fluorocarbon resin in the form of polytetrafluoroethylene, preferably Teflon from E.I. Dupont De Nemours Co., Inc. of New Jersey, also known as Dupont, is provided with multiple annular grooves near the rear end and a hollow point front end. The bullet in the preferred embodiment is characterized by having a high muzzle velocity, a very short effective range, and pulverizes on impact so as to deliver considerable hydrostatic shocking effect by delivery of all of its energy within the first two to three inches of target depth.

Abstract: A system and method are disclosed for preventing intelligible interception of information signals transmitted over a two-direction line. A masking signal is applied through a hybrid circuit at the receiving end of the line, and this masking signal, which appears on the line together with the information signal, prevents intelligible decoding. Only at the receiving end of the line, where the hybrid circuit attenuates the masking signal which it receives at its receive port, can intelligible decoding take place. Signal processing techniques used at the receiving end permit larger amplitude masking signals to be used, thus creating even greater confusion for an unauthorized detecting mechanism which is coupled to the line.

Abstract: A technique for inhibiting intelligible interception of information signals transmitted over a line from a first site to a second site. A masking signal is applied to the line immediately upon the detection of the information signal at the second site, but prior to the time at which the validity of the signal is verified. As long as the information signal remains on the transmission line, the masking signal is repeatedly turned on and off to thereby inhibit decoding of the signal by an eavesdropping device.

Abstract: A system and method are disclosed for preventing intelligible interception of information signals transmitted over a two-direction line. A masking signal is applied through a hybrid circuit at the receiving end of the line, and this masking signal, which appears on the line together with the information signal, prevents the intelligible decoding. Only at the receiving end of the line, where the hybrid circuit attenuates the masking signal which it receives at its receive port, can intelligible decoding take place. Signal processing techniques used at the receiving end permit larger amplitude masking signals to be used, thus creating even greater confusion for an unauthorized detecting mechanism which is coupled to the line.

Abstract: A semi-conductor assembly including an elongated electrically conductive support structure defining a sinuous coolant flow path between respective upper and lower surfaces of the support structure. The sinuous coolant path includes alternating concave and convex coolant surfaces. A first series of semi-conductor devices is secured in a thermally intimate manner to the upper surface of the support structure, and a second series of semi-conductor devices is secured in a thermally intimate manner to the lower surface of the support structure. Each semi-conductor device is disposed proximate a concave curved surface of the coolant path.

Abstract: There is disclosed a unitized rotating shaft assembly comprising an outer alignment sleeve within which are mounted a rotating ferrofluid seal, a first bearing, a stator a second bearing and a rotating union; there being a first follow shaft affixed to the inner races of the first and second bearing, the hollow shaft having stators mounted opposing the rotor and there being a second hollow shaft concentric with the first hollow shaft to provide separate conduits for the input and discharge of coolant.

Abstract: Means for enhancing heat transfer from liquid cooled rotating anode x-ray tubes that provide for extended surfaces on the liquid cooled concave curved heat exchange surfaces opposing the electron beam focal track. The extended surfaces take the form of fins lying in the direction of coolant flow, said fins preferably being generally triangular in cross section.