How Did Ships Communicate Before Radio?

Before the radio was invented, marine communication wasn't easy. How exactly did it work? Some methods might surprise you.

How Did Ships Communicate Before Radio?

Modern marine communication features sophisticated board systems, shore stations, and even satellites. But, of course, it wasn’t always that way. So, how did ships communicate before radio?

In the prehistoric era, the sailors would rely on horns, drums, smoke signals, and the loudness of their voices. The creation of the semaphore system finally allowed seafarers to start sending more complex messages. In the 19th century, the Morse code became the main mean of marine communication.

Keep on reading to find out exactly how all these tools worked.

How Did Ships Communicate Before Radio?

In the early ages, ships didn’t really need to communicate. Sailors knew that the available methods of communication wouldn’t allow them to have long conversations between the ships, so they tried to go over all the plans on land. During that time, signals were mainly used during an emergency.

If the ships were quite close to one another, sailors would simply shout at the top of their lungs to get their message across.

Prehistoric Era

In the prehistoric era, the means of communication that the people had on their hands were quite limited. Sailors would use smoke signals, horns, and drums to send a message.

The Chinese were the first to use smoke signals as a form of visual communication on the Great Wall of China. In such a way, the soldiers were able to inform one another about any attacks (the signals would get passed from tower to tower).

At one point, people learned to control the puffs of smoke, and each puff would represent a different letter. Of course, the signals still had to be extremely simple to ensure that the message got interpreted the right way.

Even nowadays smoke signals can be used in the sea, but only in case of emergencies (for example, to indicate the position of a castaway). Foghorns are also still used in the 21st century. In fact, such sound signals are required by federal and international laws, as they can be used as a safety tool when the view of the mariners is impaired.

5th Century B.C. – 480 B.C.

Carrier pigeons

Back in the day, carrier pigeons were one of the main ways of communication not only on land but also at sea. The birds that could carry up to 2.5 oz on their backs were used to send messages from the ship back home.

The only downside of such a method was that pigeons could carry messages only one way, and that is – to their home.

Ships could also communicate with each other by using traditional mail. If the sailors knew exactly where the other ship was heading, they could send a letter to that specific port.


Just like the carrier pigeons, a lighthouse is another method of communication between the ship and the land.

The lighthouse of Alexandria, for example, was built way back in 260 B.C. It shined 28 miles and signaled to the sailors to bring goods to the city to trade.

Speaking trumpet

Even though a speaking trumpet became a critical shipboard tool only in the 19th century, a similar tool could have been used by Themistocles in 480 B.C. during the Battle of Salamis.

18th Century

Semaphore is a method of visual communication that is used to convey a message over relatively long distances with the help of flags, disc, rods, or even bare hands. The system was developed in 1790 and involved flags of different colors (some would be used when the signal is sent across the water, while others when it’s sent over the land).

The man that was sending the signal had to hold the flags in different positions as every one of them had a different meaning.

Even though various flags were used as signals starting from ancient times, only at the end of the 18th century all the possible signals were systemized. Originally, the single message that a flag would convey was ‘come aboard the flagship for a conference’.

The flag semaphore system is still used nowadays. Even though flags are not required, the signal person would typically hold two short poles with square flags to signal letters or numbers. Each arm has eight possible directions and the flags never overlap.

19th Century

A heliograph is a simple yet effective device that can be used to transmit a visual signal over long distances. The method was used mainly on land and especially during wars.

Heliographs could have also been used in the sea. The device included shields or mirrors that reflected the light. Nowadays, a heliograph is a simple mirror with a hole in the center that can flash an ‘SOS’ to the boats in close vicinity.

Once the Morse Code was created, the heliograph could have been used to communicate using dots and dashes.

The Creation of Morse Code

In around 1847, American painter and inventor Samuel Morse, physicist Joseph Henry, and mechanical engineer Alfred Vail developed an electrical telegraph system. It is a manual system - the operator has to tap on a special key to produce the pulses of radio waves. When the pulses get to the receiver, they are audible and can be translated back to text using Morse code.

Such a system became a vital method of communication during WWII between the warships and the naval basis.

Even though Morse code can be sent with a horn or with light, it is most commonly sent by radio. Needless to say that the invention of this way of communication changed the way ships 'talk' to each other forever.


How did ships communicate before radio?

Sailors relied solemnly on visual and audible signals. Starting with horns and speaking trumpets and ending with a more complex flag semaphore system that finally allowed the ships to exchange more detailed messages.

With the creation of the radio, Morse code, and telegraph, seafarers no longer had to use smoke and lights to communicate. However, the latter can still be used in a life-threatening situation when no other methods are available.