Abstract: An independent test sight is described for a pilot's head-up display (HUD). In one embodiment, the independent test site comprises a collimator assembly and an aligned periscope assembly. The collimator assembly comprises a source of light, a reticle, and a lens for projecting the image of the reticle. The periscope assembly comprises a rhomboid prism housed within the chassis of the HUD in such a manner that it can be pivoted from a stowed position to an erect position where it projects a reticle pattern in the field of view of the HUD combiner.

Abstract: A memory unit for a aircraft flight data recorder system uses an electronically erasable solid state memory for storing the flight data and a memory controller circuit are housed in a penetration resistant, thermally insulated enclosure. Power dissipation within the insulated enclosure is minimized by an external switching circuit that applies operating potential to the solid state memory only when data are being transferred to and from the memory circuit. A data protection circuit, located within the insulated enclosure inhibits memory write and erase operations whenever the system operating potential falls below a predetermined level. In continuously storing flight data, the oldest stored data is overwritten with newly arriving flight data and the memory controller maintains an erased boundary that defines the beginning and end of the recorded data. A power monitor circuit, located outside the insulated enclosure, resets the memory controller to the erased boundary following a power interruption.

Abstract: In a ring communication system comprising selectively connectable data stations, each station has connecting circuitry including a phase-locked loop arrangement (111) which is frozen at its current frequency and phase in response to a signal interruption caused by a station insertion or removal operation. Control logic (113) generates a freeze control signal in dependence of the signal energy status on input lines (75). This control signal activates gates (149, 151) and switches (155, 157) to interrupt change control signals of the phase-locked loop circuitry and to keep an oscillator control voltage at a given value. The control logic also provides an auxiliary data signal during the freeze interval which is applied to the ring to keep stations downstream in synchronism. By this method and arrangement, undesired reactions and excursions of the phase-locked loop circuitry in response to a signal energy outage are prevented, and synchronization can be rapidly regained after station insertion or removal.

Abstract: A digital symbol generator for developing analog deflection voltages to drive a cathode ray tube display forming a plurality of symbols from successive blanked and unblanked vectors rotatable about an arbitrary angle of rotation. Each vector is specified by a binary representation of its polar coordinates including vector angle and length, rotation being accomplished by digital addition of the vector angle and angle of rotation. A line length counter generates a pulse train the number of pulses of which is proportional to vector length and the frequency of which is greater for blanked vectors than for unblanked vectors so that blanked vectors are drawn at a faster rate. Symbol error checking is accomplished by a vector closure technique wherein the symbology end point is measured at the output of the symbol generator and compared with the independently calculated true end point.

Abstract: A circuit for computing a signal representing the pitch attitude of an aircraft utilizes angle of attack based information and the output of a gyroscope to produce a calculated pitch signal which has a long term component dependent upon the angle of attack based information and a short term component dependent upon the gyroscope output signal. The calculated pitch signal may be used to pitch stabilize a head up display in the aircraft and in this event is modified with a correction signal derived from the pitch signal and the output of a head up display mounted accelerometer. Alternatively, the pitch signal may be combined with a signal representing the difference between the output of the display mounted accelerometer and the output of an angle of attack vane mounted accelerometer to provide a pitch stabilization signal which is free of turn and shear errors.

Abstract: A process for the recovery of valuable metals from spent desulfurization catalyst wherein the catalyst, which has not been subjected to oxidative roasting, is thermally reduced in the presence of carbon and calcium oxide.

Abstract: In a communication network comprising block switching nodes interconnected by transmission links, a flow control mechanism is provided in each switching node for regulating the flow of addressed data blocks or messages. A hardware look-ahead mechanism effective within each node tests for each data block received from a link and buffered at an input port, whether it can be accepted at the appropriate output port of the same node for further transmission. A token mechanism effective over links permits maintenance at each output port of a node of an indication whether any data block can be accepted in the input port at the other end of the respective link. By the combined operation of look-ahead mechanisms and token mechanisms the flow of addressed messages in a direction where the transmission path is already filled up is prevented. This has a positive smoothing effect on overall traffic flow where short-time or local overloads occur.

Abstract: A cable structure comprising a cable provided with a cable sheath in the form of a flexible corrugated or undulated tube. Between the cable and the sheath there are arranged guide bodies at predetermined locations. The guide bodies are fixed at the inside of the sheath and are provided with domed or arched guide surfaces at the side of the cable, in order to guide the cable both in a straight and bent condition.

Abstract: A head-up visual approach instrument having a display of flight guidance information for a two-segment approach to touchdown. The display includes flight path indicia which the pilot aligns with an outside world aiming point, as the touchdown zone of a runway. During the first segment the flight path indicia is positioned as a function of aircraft altitude to define the changing sight angle to the target.