Editing Decca Navigator System (section)

=== Multipulse ===
''Multipulse'' provided an automatic method of lane and zone identification by using the same phase comparison techniques described above on lower frequency signals.

The nominally continuous wave transmissions were in fact divided into a 20-second cycle, with each station in turn simultaneously transmitting all four Decca frequencies (5''f'', 6''f'', 8''f'' and 9''f'') in a phase-coherent relationship for a brief period of 0.45 seconds each cycle. This transmission, known as Multipulse, allowed the receiver to extract the 1''f'' frequency and so to identify the lane that the receiver was in (to a resolution of a zone).

As well as transmitting the Decca frequencies of 5''f'', 6''f'', 8''f'' and 9''f'', an 8.2''f'' signal, known as Orange, was also transmitted. The beat frequency between the 8.0''f'' (Red) and 8.2''f'' (Orange) signals allowed a 0.2''f'' signal to be derived and so resulted in a hyperbolic pattern in which one cycle (360°) of phase difference equates to 5 zones.

Assuming that one's position was known to this accuracy, this gave an effectively unique position.