—Charles H. Cugle, Cugle’s Practical Navigation, 1936

(If the flags In A’s hoist cannot be made out, B keeps her answering pennant at 
the “Dip” and hoists the signal “OWL” or “WCX.”)

CXL Do not abandon me.
A I am undergoing a speed trial.
D Keep clear of me—I am maneuvering with difficulty.
F I am disabled. Communicate with me.
G I require a pilot.
P Your lights are out, or burning badly.
U You are standing into danger.
X Stop carrying out your intentions.
K You should stop your vessel instantly.
L You should stop. I have something important to communicate.
R You may feel your way past me.