The "10 Code," also known as ten signals, is a brevity code used by law enforcement and emergency services to communicate efficiently over radio transmissions. Each code begins with the number 10, followed by a specific number that represents a particular message or situation, such as 10-4 for acknowledgment or 10-20 for location. Originally developed in the 1930s, the 10 Code helps reduce misunderstandings and keeps radio traffic concise. While widely used in the United States, some agencies have moved away from it in favor of plain language to enhance clarity, especially in multi-agency responses during emergencies.