RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
using amplitude comparison of signals transmitted sequentially from antennas or antenna systems having differently-oriented overlapping directivity characteristics, e.g. equi-signal A-N type
the signals being transmitted sequentially from an antenna or antenna system having the orientation of its directivity characteristic periodically varied, e.g. by means of sequentially effective reflectors
