Navigation and Seamanship

4.2.5.5. Flashing light signaling

Specially prepared flashing lights are used for the signals at sea.Flash lights are used only during night hours. Most of the signal lights are unidirectional. The standard rate of signaling by flashing light is to be regarded as forty letters per minute. In selecting a flashlight, ensure that it is water resistant and that it is designed to withstand shocks and also seals out moisture. The case should be made of non-slip rubber. A red plastic disc should be inserted in the lighted end to provide a red light for sustaining your night vision or to prevent unnecessarily lighting up the bridge at night