what does 10-4 mean?

TLDR: "10-4" is a radio communication code meaning "Acknowledgement," originating from the ten-codes developed in the late 1930s for efficient communication in law enforcement. It has since become a cultural staple, widely recognized in various contexts, including trucking and popular media.

The phrase "10-4" is a well-known radio communication code that signifies "Acknowledgement." Developed in the late 1930s by Charles Hopper for the Illinois State Police, it was part of a system designed to streamline communication among law enforcement officers. The ten-codes were published in 1940, allowing for quick and clear exchanges, which were crucial given the limited radio channels available at the time. While some police departments have shifted to plain language, "10-4" remains a widely recognized term in both professional and casual settings.

In addition to its use in law enforcement and military contexts, "10-4" has been adopted by the trucking industry, where it is commonly used in CB radio communication to confirm receipt of messages. Its cultural significance has grown, appearing in movies and everyday conversations as a casual way to say "OK" or "understood." Despite evolving communication practices, "10-4" continues to be relevant, serving as a testament to the importance of clear and concise messaging.