Abstract: A passive method for an aircraft to use its on-board locating apparatus to monitor interrogation signals and ISLS signals transmitted by at least one secondary surveillance radar, and coded reply signals transmitted by at least one fixed ground transponder; to match said transponder reply signals with said ISLS signals, in order to associate said transponder reply signals with interrogations from said radar; to repetitiously compute said aircraft's instantaneous position in space, said computations being based on hyperbolic and linear functions related to said aircraft, said radar, and said associated fixed transponder; and to display said positions for navigational purposes.

Abstract: An angulated retaining wall comprised of a plurality of adjoining posts is disclosed for retaining a wall of material having gradual and/or abrupt changes in direction in its face. The retaining wall is comprised of corner-groove combinations wherein a corner of a post is disposed at a desired direction into a groove of an adjoining post and wherein the preferred angularity of said groove is less than that of the predetermined angularity of said corner. At the maximum disposition a first side of a corner will be parallel to and overlap in supportive contact with a first sidewall of said groove by a predetermined dimension between said corner and the edge of the first sidewall, and the adjacent side of said corner will be in supportive contact with the edge of the second sidewall of said groove. At an intermediate disposition the first side and the adjacent second side of said corner will be in supportive contact with the edges of the first sidewall and the second sidewall respectively of said groove.

Abstract: A ported speaker enclosure is disclosed for extending the low-frequency range of the enclosure and increasing the intensity of the low-frequency range of reproduced sound wherein the size of the enclosure, the locations of the speakers, and the size and locations of the ducted ports are determined by relatively simple relationships based solely on speaker cone dimensions. In one form, a ducted port speaker enclosure is comprised of two bass-range speakers, or woofers, wherein one woofer is located in a predetermined position above the other on the enclosure. An open sector of a plurality of open sectors of the frame at the back of the topmost speaker faces towards the top and an opposite open sector faces towards the bottom of the enclosure of the two woofer system. A sound damping material is added to cover the top and bottom facing sectors of the topmost speaker. Insulation material of predetermined dimensions is affixed to the inside walls of the right and left sides of the enclosure.

Abstract: A single varactor diode parametric amplifier is described which has a broadband termination at the upper sideband frequency in the pump waveguide. This termination presents an open circuit condition at the upper sideband frequency, which, in combination with an upper sideband fequency choke on the input signal circuit transmission line achieves low noise, high gain characteristics with minimum interaction with the input signal, pump, and idler circuitry. Theoretical noise figures can be obtained at low power consumption, high gain, and broadband performance.