In 1837, Samuel Morse and his colleague Alfred Vail invented a way to send messages across great distances by turning words into dots and dashes. This system of encoding information was an early form of digital communication.
The telegraph they built worked on the principle of sending electricity through a wire circuit. A battery formed a circuit when someone pressed the switch, sending current in one direction or not at all. The presence or absence of that current sent pulses of electricity down the line, which could be turned into dots and dashes as they traveled along the wires.
To translate letters into dots and dashes, operators used a source alphabet of the 26 English letters. They translated those letters into a target alphabet of dots and dashes, using short presses (dots) and long presses (dashes). Each character was transmitted separately with pauses between them. When the signal arrived at the receiving end, an operator decoded it as the signals came in.
Thomas Edison famously learned to decode messages by ear before he could read them.
Morse code is efficient because it uses only two symbols—on and off—and encodes information in a binary tree. Since each letter has a different combination of dots and dashes, you can send more information quickly than if you had to use the same number of characters for each letter. This variable-length system became the basis for all later codes.
Historical Uses and Lasting Importance
Morse code was revolutionary because it allowed people to communicate across vast distances much faster than they ever had before. Messages could be carried from place to place much more quickly than by foot or horse, and more accurately than by smoke signals or flags.
During World War II, Morse code was essential to the war effort. Ships stayed in touch with their home bases and shared critical information and intelligence about enemy movements. As Ngaire Bushell notes in her history of the HMS Belfast, “Morse code enabled ships to communicate instantly with other vessels and shore stations.”
But Morse code also had its vulnerabilities. Enemy aircraft and ships could intercept a ship’s radio transmissions, allowing them to find targets. To avoid interception, ships near friendly forces used Aldis lamps or signal flags to talk to nearby ships.
Morse code was so important to communications that it laid the groundwork for today’s telecommunications. In the 19th century, companies laid tens of thousands of miles of cable to connect the world. By the end of the century, they were laying cables under the Atlantic Ocean. Today, we have similar systems of cables connecting us globally.