In APCO, Association of Public-Safety Communications Officials 10-codes, 10-9 means "Repeat Message" or "Say Again". It is used to request that the previous radio transmission be repeated because it was unclear, missed, or interrupted.
Here’s how it might be used in a real-world scenario:
- Dispatch: "Unit 12, proceed to 5th Avenue and Pine Street."
- Officer: "10-9, repeat your last message."
In this exchange, the officer is indicating that the message was not received clearly and requires repetition. Using 10-9 ensures that critical information is accurately understood and prevents miscommunication during operations.
Historical Background
The 10-9 code originated in the early APCO 10-code system to address the limitations of two-way radio communications, which were often prone to static, interference, or signal loss. Early public-safety operations required a concise, standardized way to request message repetition without creating radio congestion.
By using 10-9, officers and dispatchers could quickly signal that information needed to be repeated, preserving efficiency while ensuring operational accuracy.
Operational Usage
In practice, 10-9 is used whenever a transmission is unclear, distorted, or partially missed. It can be issued by officers, dispatchers, or other units to maintain effective communication and situational awareness.
Typical scenarios include:
- Messages distorted by interference, weather, or terrain
- Busy or overlapping radio traffic making the initial transmission unclear
- Accidental omission or mishearing of important details
- Confirming critical instructions during emergencies or tactical operations
Once the message is repeated, the receiving unit can acknowledge it using 10-4 (acknowledgment) to confirm clarity and understanding.
Variations And Regional Interpretation
While 10-9 is widely recognized as “repeat message,” some agencies may use it selectively, preferring plain-language commands like “say again” or “please repeat” in multi-agency operations. Regional differences in 10-code usage mean that personnel must often adapt based on local protocol.
Plain-Language Alternatives
Agencies favoring plain-language communication may replace 10-9 with phrases such as:
- "Say again."
- "Please repeat."
- "Message unclear, repeat."
These alternatives reduce ambiguity, especially when units from different jurisdictions are sharing radio frequencies.
Modern Relevance
Even with advanced radio technology, CAD systems, and digital messaging, 10-9 remains important in real-time voice communications. It provides a quick, universally understood signal to request repetition, helping prevent errors in mission-critical information flow.
Related 10-Codes
Codes commonly associated with 10-9 include 10-1 (signal weak), 10-2 (signal good), 10-4 (acknowledgment), and 10-3 (stop transmitting). Together, these codes help maintain clear and effective radio communication under all operational conditions.