What modern system of a very old messaging method entails red and yellow ('Oscar') at sea, and white and blue ('Papa') on land?
Semaphor Flag semaphore Semaphore (communications) Semaphore (communication) Semaphore flags Shipping signals Semaphore alphabet Semifore Signaling, Semaphore procedure Japanese semaphore Semaphore Semafore Semaphore flag signalling Semaphore (comunication) Flag semaphore code Flag semaphore codes Semaphore flag Semaphone
semaphore communication flag semaphore codes semaphor semaphore communications semafore semaphore comunication flag semaphore code semaphore flag signalling semaphore flags semaphore flag semaphore semaphone japanese semaphore semaphore alphabet signaling semaphore procedure shipping signals flag semaphore semifore
flag semaphore
WikipediaEntity
Flag semaphore