In APCO, Association of Public-Safety Communications Officials 10-codes, 10-3 typically means "Stop Transmitting" or "Cease Radio Traffic". It is used to instruct units to halt non-essential transmissions, often to reduce interference or allow priority traffic to be heard clearly.
Here’s how it might be used in a real-world scenario:
- Dispatch: "All units, stand by. 10-3."
- Officer: "Copy."
In this exchange, dispatch is directing all units to stop transmitting so that important or sensitive radio traffic can proceed without interruption.
The code is most commonly used during emergencies, high-risk incidents, or situations where background chatter could interfere with critical communications.
Historical Background
The purpose of 10-3 emerged early in the development of the APCO 10-code system, when radio channels were shared and highly susceptible to interference. With limited frequencies available, even brief overlapping transmissions could render messages unintelligible.
By using a short, standardized command like 10-3, dispatchers could quickly impose radio discipline, ensuring that only essential transmissions were broadcast during critical moments.
Operational Usage
In active operations, 10-3 is typically issued by dispatch, though field supervisors may also direct units to cease transmissions. It applies to routine and non-essential radio traffic, not to emergency declarations.
Situations where 10-3 is commonly used include:
- Active pursuits or tactical operations
- Officer-in-distress situations such as 10-0
- Emergency broadcasts or alerts
- Heavy radio congestion affecting clarity
Once a 10-3 is in effect, units are generally expected to remain silent unless they have urgent or authorized information to transmit.
Variations And Regional Interpretation
While 10-3 is widely recognized as a command to stop transmitting, some agencies use it more narrowly to restrict only non-essential chatter, while others interpret it as a complete radio freeze.
In certain jurisdictions, similar instructions may be issued using alternative codes or plain-language commands, depending on departmental policy and interoperability requirements.
Plain-Language Alternatives
Agencies that favor plain-language communication often replace 10-3 with direct instructions such as:
- "Clear the air."
- "All units hold traffic."
- "Stop radio traffic unless emergency."
These phrases reduce ambiguity, particularly during multi-agency responses where not all personnel may share the same code set.
Modern Relevance
Despite a broader shift toward plain-language radio communication, 10-3 remains common due to its brevity and immediate recognition. Its use continues in both formal procedures and informal radio culture.
Whether spoken as a code or in plain language, the function of 10-3 remains essential: preserving radio clarity during moments when every second and every word matter.
Related 10-Codes
Codes frequently associated with 10-3 include 10-0 (officer in trouble), 10-1 (signal weak), 10-2 (signal good), and 10-33 (emergency traffic). Together, these codes help manage radio priority, clarity, and control.