USCG Exam PracticeChart symbols and abbreviations (Chart No. 1)
A light is charted as 'Iso R 6s'. Which of the following correctly describes this light's characteristic?
- A. A red light that flashes once every 6 seconds with a flash shorter than the eclipse
- ✓ A red light with equal periods of light and darkness, completing one full cycle in 6 secondsCorrect
- C. A red light that is continuously on for 6 seconds, then off for a shorter period
- D. A red light that occultes once every 6 seconds, with darkness shorter than the light period
Why B is correct
Isophase (Iso) means equal periods of light and darkness. 'Iso R 6s' therefore describes a red light where the light period and dark period are equal, with the total cycle period being 6 seconds.