Abstract: An aircraft display system positions a synthetic runway which is properly aligned with a target runway even during crosswind approaches. The relative position of the target runway is computed in a manner which reduces the accumulated error associated with previous systems. The lateral deviation rate of the aircraft relative to the extended centerline of the target runway is computed from data provided by various aircraft navigation and sensor systems. A track error angle representative of the difference between the extended centerline of the runway and the ground track of the aircraft is computed from the lateral deviation rate and ground speed. Runway bearing relative to ground track is computed from the track error angle and lateral deviation angle. Compensating runway bearing relative to ground track with drift angle yields a runway bearing relative to aircraft heading which is useful for positioning a synthetic runway on a display.

Abstract: The apparatus detects a difference of frequency between a first signal having a first frequency and a second signal having a second frequency, the first and second signals being digital signals. A phase shifter shifts the first signal such that the first signal and the shifted first signal are sufficiently out of phase to keep the rising and falling edges of the two signals from occurring at the same time thereby avoiding subsequent simultaneous triggering conditions and jitter conditions between the first and second signal. A first gate samples the second signal by the shifted first signal to output a first sampled signal. A second gate samples the second signal by the first signal to output a second sampled signal. A sample gate samples the first sampled signal and the second sampled signal to generate a difference signal, the difference signal containing a difference value of the frequency difference between the first and second signal.

Abstract: A fault detection apparatus and method combines each of a plurality of redundant digital data signals with a unique key signal for transmission over one of a plurality of signal lines and recombines each with its unique key signal at a receiving end. The recombined signals are then compared at the receiving end to detect certain faults between or among the plurality of what should be identical received signals.

Abstract: A method and apparatus for determining the level of slag containing iron or iron compounds in the bottom of a glass melting furnace is disclosed. Electrically conductive electrodes or probes are placed in a predetermined position in the furnace. When the iron containing slag touches the electrodes or probes, the resistance between the electrodes or probes decreases or the current flowing between them increases activating a signal or alarm to warn the operator of the level of the slag in the furnace.