464 HANDBOOK OF ELECTRICAL ENGINEERING
- White and red lights flashing the Morse letters ‘U’ every 15 seconds as follows:
Eclipse 1.00 s
Flash 1.00 s
Eclipse 1.00 s
Flash 3.00 s
Eclipse 8.00 s
Total Period 15.00 s- Fog signals sounding the ‘U’ every 30 seconds as follows:
Blast 0.75 s
Silent 1.00 s
Blast 0.75 s
Silent 1.00 s
Blast 2.50 s
Silent 24.00 s
Total Period 30.00 s- Illuminated identification panels.
- Navigation buoys.
18.2.2 White and red flashing lights
The ‘normal’ range and ‘apparent intensity’ of these flashing lights should be in accordance with
the local requirements, e.g. for UK waters, IALA publication ‘Recommendations for the Notation of
Luminous Intensity and Range of Lights’. Appendix II (16th November 1996) and BS 942 (1949)
clauses 10 and 11 respectively.
18.2.2.1 Main lights
The main white lights should have a ‘nominal’ range of 15 miles and be visible in every direc-
tion of approach, there should normally be a minimum of two and a maximum of four main
white lights.
18.2.2.2 Subsidiary lights
Subsidiary red lights of 3 miles ‘nominal’ range should be positioned to mark the horizontal extrem-
ities of the structure, in positions not occupied by white lights, to indicate any irregular projections
of the complex.
18.2.2.3 Secondary lights
Secondary white lights of 10 miles ‘nominal’ range and visible in every direction of approach should
automatically come into operation in the event of failure of the 15 mile main white lights; these are
normally mounted in similar location to the main white lights.