Abstract: A passive aircraft Traffic alert and Collision Avoidance device (TCAD) is based on sensing and responding to transponder replies of other aircraft to SSR interrogations. In order to avoid masking other aircraft replies by the host transponder TCAD repeatedly and randomly suppresses the host transponder and simultaneously listens for other aircraft replies. Suppression on each occasion is effective for an equal and predetermined duration which is much longer than a typical reply, in a preferred embodiment the suppression/listen duration is 725 .mu.s. In this embodiment the time between successive suppression/listen occasions is random between 725 .mu.s. and 5.025 ms. with an average value of about 2.9 ms. Digital signal processing is used to detect and discard garbled or overlapping replies. Each valid reply, exhibiting a minimum pulse amplitude, is decoded and correlated with a calibrated range parameter and given a time tag.

Abstract: This invention relates to insulation materials and, in particular, to thermal insulation materials having heat reflective properties.In particular insulation material according to the invention comprises a random array of elements as herein defined having at least a portion thereof deformed so as to increase the resilience of the elements and to assist in forming spaces between adjacent elements in the random array.In this specification the term element is used to include filaments of different cross-sectional shape, for example, circular, square or rectangular, strips of uniform or non-uniform width and/or thickness, flakes and platelets of regular or irregular geometric shape and of uniform or non-uniform thickness, and the like.

Abstract: A storm mapping system detects electrical activity caused by weather phenomona such as lightning strokes, and the like and displays information related to the electrical activity indicative of storm location in a frame of reference in which the observation location is taken as the origin. In order to give the observer good spatial understanding, signals detected from a relatively close disturbance (which produces relatively large signals) are displayed relatively close to the observation location as compared to display of signals generated from a relatively further disturbance which produces relatively smaller signals which are displayed relatively far from the observation location. The limited resolution display is effectively driven by signals read from digital storage wherein mapping between the different display segments and digital storage is maintained.

Abstract: A low profile electric field sensor is arranged to sense electric field potentials with respect to a local ground plane. The sensor includes an antenna in a generally planar format with a major dimension extending generally parallel to the local ground plane. To maintain signal to noise ratio, while at the same time minimizing the height of the antenna so as to provide a low profile, the antenna is coupled to a charge amplifier. The charge amplifier comprises an operational amplifier, preferably with a capacitor feedback between output and an inverting input, and the antenna is conductively connected to the inverting input.

Abstract: A storm mapping system detects electrical activity caused by weather phenomena such as lightning strokes and the like and displays information related to the electrical activity as indicative of storm location with reference to an origin which is taken as the observer's location. A cathode ray tube (or other display means) provides a display and locations thereon are illuminated in response to the electrical activity. The azimuth of the display is indicative of the azimuth of the electrical activity. The distance from the reference location to any illuminated location is a function of the signal strength. Although signal strength is not a precise indicator of distance, it is a useful data item in that the more severe storms generate the maximum signal strengths. In contrast to the prior art systems, the storm mapping system of this invention illuminates a location whose distance from the origin is inversely related to signal strength.

Abstract: A digital tuning device for accurate selectable tuning of a resonant circuit. The inductive and capacitive elements of the resonant circuit are connected by a transformer device whose turns ratio is variable in accurate digital increments. Since the reflected reactance is related to the square of the turns ratio and since the resonant frequency varies as the inverse square root of the reactance, the resonant frequency of the circuit is directly related to the turns ratio.