US PATENT SUBCLASS 342 / 397
.~.~.~.~ Decca

Current as of: June, 1999
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342 /   HD   COMMUNICATIONS: DIRECTIVE RADIO WAVE SYSTEMS AND DEVICES (E.G., RADAR, RADIO NAVIGATION)

350  DF  DIRECTIVE {10}
385  DF  .~ Beacon or receiver {2}
386  DF  .~.~ With transmisson of bearing or position determinative signals {6}
394  DF  .~.~.~ Iso-phase type {3}
397.~.~.~.~ Decca

DEFINITION

Classification: 342/397

Decca:

(under subclass 394) Subject matter wherein sets of hyperbolic lines of position are determined by comparison of the phase of (1) one reference continuous wave signal from a centrally located master transmitter with (2) each of several continuous wave signals from plural slave transmitter located in a star pattern, each about 70 nautical miles (130 kilometers) from the master.

(1) Note. Decca is a radio navigation system which transmits on several frequencies near 100 kilohertz and is generally useful to about 200 nautical miles (370 kilometers).

(2) Note. A typical decca transmitting chain comprises a master station which is referred to by the "color" of the phase meter associated with each at the receiver. Each station transmits a stable continuous-wave frequency that bears a fixed relationship to the frequencies of other three stations, and therefore phase comparison produces a family of hyperbolic lines of position where the phases are equal (the spaces between the lines are called lanes).

SEE OR SEARCH CLASS

701, Data Processing: Vehicles, Navigation, and Relative Location,

219, for computerized navigation apparatus using decca equipment.