Interlocking equisignal system
A system of radio navigation by a comparison method in which two alternating transmissions are used which produce, in the region of the required track, signals which are operationally complementary.
On the defined track the resultant composite signal has a constant intensity.
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