A-N Radio range
A Radio Range providing four radial lines of position identified aurally as a continuous tone resulting from the interlocking of equal amplitude A and N International Morse Code letters.
The sense of deviation from these lines is indicated by deterioration of the steady tone into audible A or N code signals.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM