A display system provides a real time display on its display screen of the present and recent past operating history of an operating system. The operating system provides a signal to the display system in real time which encodes the current operating state of the operating system. For each operating state, a line is displayed in the display screen at a coordinate position which associates the line with the operating state. Each of these lines is coordinated with a time scale running along the screen which indicates the actual time intervals during which the various states existed.

An area navigation device automatically establishes waypoints along an RNAV course line intersecting with the four cardinal radials of VORTAC stations. For a given VORTAC station, the pilot selects any of the four cardinal radials and is automatically provided with the distance from the VORTAC station, along that cardinal radial, as the intersection with his selected RNAV course line. Thus, a pilot can quickly sequence through the cardinal radials and quickly ascertain the availability of waypoints along that radial. After an automatically generated cardinal waypoint is selected, it is automatically entered into memory dedicated to that waypoint for later recall and conventional use in area navigation.

A very high frequency omni-range (VOR) receiver for use in aircraft radio-navigation, which provides an indication of course deviation that is substantially immune to effects such as reflections in transmitted VOR signals, transients occurring in an aircraft's electrical system and propeller and/or rotor modulations of an incoming VOR signal and the like which are all unrelated to actual course deviation, is disclosed. The receiver phase synchronizes a signal from a 1.08 MHz crystal oscillator to a 30 Hz reference signal and a 30 Hz variable signal; both the reference and variable signals are received from a VOR ground station. As a result of the phase synchronization, the receiver produces timing pulses which are accurately phase synchronized to a synchronized reference pulse stream derived from the 30 Hz reference signal. Additionally, the receiver produces a synchronized variable pulse stream that is derived from the 30 Hz variable signal. The receiver produces, in response to the synchronized reference pulse stream and the timing pulses, a signal (henceforth referred to as the "OBS" signal) which is phase shifted by an amount representative of a selected radial emitted by that station. To facilitate determining deviations from the selected radial, the receiver determines any phase difference between the "OBS" signal and the synchronized variable pulse stream. This phase difference is used to produce a deviation signal having a value that represents any course deviations existing between the selected radial and a present magnetic course of the aircraft with respect to the VOR station.

A hand held navigational-communications transceiver is compressed into a case having a volume of about 37 cubic inches by defining functional implementation for VOR (VHF omni-directional range) navigation. The transceiver can be selectively switched to process and display directional radial information. A microprocessor circuit provides primary circuitry information in combination with transceiver function software held in ROM (read only memory). A plurality of pre-programmed frequencies may be selected.