List of Police 10 Codes: From “10-4” to Plain Language

“10-4, good buddy.” The phrase is a classic piece of Americana, instantly recognizable from movies, television, and CB radio culture. For decades, police 10-codes have been the semi-secret language of law enforcement, a rapid-fire shorthand crackling over the airwaves. But this iconic system is now at the center of a significant debate about public safety.

This guide explores the world of police communication. We will cover the history of 10-codes and why they were invented. We will also examine the serious problems they can cause and the national push to replace them with plain language. This report provides comprehensive reference lists for anyone interested in law enforcement, from private investigators to curious citizens.

Cracking the Code: What Are Police 10-Codes?

Police 10-codes are a system of numerical signals used for two-way radio communication. Each number corresponds to a common phrase or message, allowing officers to speak quickly and efficiently. For example, instead of saying “I have received and understood your message,” an officer can simply say “10-4.”

These codes, also known as ten-signals, were designed to serve two main purposes. The primary goal was to make radio transmissions brief and clear. This saved valuable time and kept radio channels open for other officers. A secondary goal was to add a layer of privacy, making it harder for the general public to understand sensitive police communications.

The structure of the codes was a clever solution to a technical problem of the time. Early police radios in the 1930s used vacuum tubes and a power system called a dynamotor. This equipment needed a fraction of a second to “spin up” to full power after the microphone button was pressed. As a result, the first word of a transmission was often cut off or garbled. By starting every code with the word “ten,” it gave the radio transmitter time to warm up, ensuring the critical number that followed was heard clearly.

A Broadcast from the Past: The Origin of 10-Codes

The story of 10-codes begins in the 1930s, a time when police radio technology was still new and channels were limited. The credit for inventing the system goes to Charles “Charlie” Hopper, the communications director for the Illinois State Police, District 10. Around 1937, Hopper developed the codes to reduce speech on the radio and standardize common messages.

The idea quickly gained traction. In 1940, the Association of Public-Safety Communications Officials (APCO) published the first official list of ten signals. APCO continued to expand and revise the codes over the following decades, with significant updates in 1955 and 1974. The system spread to law enforcement agencies across North America and became an ingrained part of police culture.

The codes eventually entered the public imagination. The popular 1950s television series Highway Patrol frequently featured officers using the codes, making phrases like “10-4” famous. This popularity led to their adoption by CB radio enthusiasts, cementing their place in popular culture. However, the “official” nature of the codes was always limited. APCO provided recommendations, but there was no central authority to enforce a single, universal standard, a fact that would create serious problems in the future.

The Standardization Problem: A Tower of Babel

The greatest weakness of the 10-code system is the lack of standardization. There is no truly universal set of codes, meaning their definitions can change dramatically from one jurisdiction to the next. This creates a significant risk of confusion, especially when multiple agencies must work together.

A perfect example highlights the risk. In Washington, D.C., the code “10-50” means a car accident. But in neighboring Montgomery County, Maryland, just a few miles away, “10-50” means an officer needs immediate help. Such a critical difference in meaning could lead to a tragic miscommunication during a significant incident involving both departments.

This is not an isolated issue. It is rare to find two police departments that use the same set of codes. This has created a communications “Tower of Babel” for first responders. During large-scale emergencies that require a mutual aid response, officers from different cities, counties, or states may find themselves on the same radio channel, unable to understand each other’s coded language. This lack of interoperability is not just an inconvenience; it is a direct threat to officer and public safety.

The consequences of these communication failures have been documented in after-action reports for the nation’s worst disasters. Both the 9/11 Commission Report and reviews of the response to Hurricane Katrina identified massive communication breakdowns as a key factor that hampered rescue efforts. When different agencies cannot communicate clearly, command structures break down, resources are not deployed effectively, and lives are put at risk.

A New Directive: The National Push for Plain Language

In response to the lessons learned from major incidents, there has been a national push to move away from 10-codes and toward “plain language.” This initiative is led by federal agencies, including the Department of Homeland Security (DHS) and the Federal Emergency Management Agency (FEMA). Since 2005, FEMA has officially discouraged the use of 10-codes to improve communication between agencies.

The push for plain language is a core component of the National Incident Management System (NIMS). NIMS provides a comprehensive framework for managing emergencies of all sizes, from local incidents to national disasters. Under NIMS, the use of plain language—meaning everyday, clear English without codes or jargon—is required for all multi-agency, multi-jurisdiction events.

Federal guidelines also strongly encourage agencies to use plain language for their day-to-day internal operations. The reasoning is simple: practicing with plain language every day builds fluency. It ensures that when a significant disaster strikes, clear communication is second nature. This eliminates the risk of code-related confusion and ensures that all responders—police, fire, EMS, and federal partners—can work together seamlessly. This shift is part of a much larger post-9/11 change in public safety philosophy, focusing on interoperability and unified command to prevent the communication failures of the past.

The Debate: Tradition vs. Interoperability

The transition to plain language has not been without controversy. Many law enforcement agencies have been resistant to giving up their 10-codes, leading to a debate that pits tradition against modern safety protocols. This conflict is less about which system is better and more about the challenge of changing an entrenched culture.

Arguments for keeping 10-codes often center on three points. First, they are fast and efficient for common messages. Second, they are a deeply ingrained part of police culture and tradition, a unique language that fosters a sense of identity among officers. Third, some believe the codes provide a layer of security, preventing civilians or suspects from understanding radio traffic.

However, advocates for plain language offer strong counterarguments. While codes can be fast, their potential for misinterpretation during a crisis outweighs the benefit of speed. The argument for tradition is challenged by the clear evidence from after-action reports that non-standard codes are a safety liability. Finally, the privacy argument is essentially a myth. With police scanners widely available and code lists published online, anyone can learn the codes. Proper radio security comes from modern encryption technology, not from easily deciphered jargon. Ultimately, the push for plain language is a move toward evidence-based safety standards, even if it means letting go of a long-held tradition.

Beyond the “10”: Other Police Radio Codes

While 10-codes are the most famous, they are not the only system used in law enforcement. Different agencies have developed their own unique sets of signals to meet specific needs. Understanding these variations provides a more complete picture of the diverse landscape of police communication.

For example, the California Highway Patrol (CHP) uses a system of “eleven-codes.” In this system, “11-99” means an officer needs emergency assistance. Other agencies, like the Port Authority Police in New York and New Jersey, have used “eight codes.”

In California and other areas, it is also common for officers to use penal code numbers as shorthand. An officer might report a “187,” which is the California penal code for murder, or a “502,” an old vehicle code for a drunk driver. These numeric codes, along with 10-codes and 11-codes, all serve the same purpose: to convey complex information with a simple, quick signal.

Ensuring Clarity: The Phonetic Alphabet

In police work, accuracy is critical. Mishearing a single letter in a license plate number or a street name can have serious consequences. To prevent these errors, law enforcement uses phonetic alphabets to spell out important information over the radio.

Just like with 10-codes, there has been a historical tension between a traditional system and a modern, universal standard. For many years, the most common system was the APCO phonetic alphabet, first published in 1940. This alphabet uses simple words like “Adam,” “Boy,” and “Charles.” It remains in widespread use today by many departments, including the Los Angeles Police Department, and has become famous through TV shows like Adam-12.

However, in 1974, APCO officially adopted the International Civil Aviation Organization (ICAO) alphabet, also known as the military phonetic alphabet. This system uses words like “Alpha,” “Bravo,” and “Charlie.” It was adopted to promote a universal standard that aligns with military, aviation, and international use. Despite this official change, the older APCO system persists, demonstrating the same cultural inertia seen in the 10-code debate.

Reference: Master Lists of Law Enforcement Codes

The following tables provide a comprehensive reference for standard police codes, signals, phonetic alphabets, and acronyms. Note that the meanings of 10-codes and other signals can vary significantly by location. These lists represent the most common uses.

Table 1: Common Police 10-Codes and Their Meanings

Table 2: Police Scanner Codes, Signals, and Other Numeric Codes

Table 3: The Military & ICAO Phonetic Alphabet (Current Standard)

Table 4: The APCO & Civilian Phonetic Alphabet (Legacy System)

Table 5: Common Law Enforcement Acronyms and Abbreviations

A Note for Hobbyists: Amateur Radio Q-Codes

Radio enthusiasts need to know that police codes are different from the codes used in amateur (Ham) radio. Ham radio operators use a system called “Q-codes,” which originated in Morse code communications. For example, “QTH” means “My location is…” and “QSY” means “Change to transmission on another frequency.”

The use of 10-codes is actively discouraged in the amateur radio community. This is to prevent confusion and maintain the distinct operating procedures of the hobby. If you are communicating on amateur radio frequencies, always use the proper Q-codes or plain language, not police 10-codes.

The Future of the Frequency: Conclusion

The journey of police communication reflects the evolution of technology and public safety strategy. What began as a clever technical fix in the 1930s grew into a cultural touchstone for law enforcement. For decades, 10-codes served their purpose, providing a fast and efficient shorthand for officers on the beat.

However, the hard lessons learned from national tragedies have exposed the system’s critical flaw: its lack of standardization. In a world that demands seamless multi-agency cooperation during a crisis, a fragmented language is a liability we can no longer afford. The clear direction from national leadership and the overwhelming evidence from after-action reports point toward a future where plain language is the standard for all critical public safety communication.

While 10-codes will likely survive in some form for internal, day-to-day use, their role in major incidents is ending. The future of the frequency is one of clarity, interoperability, and a common voice, ensuring that when disaster strikes, every hero speaks the same language.

Sources

• 9-11 Commission Hearing | Report | Recommendations
• AMU Edge
• NSTC Equity and Law Enforcement Data
• National Incident-Based Reporting System
• Law Enforcement Core Statistics
• Chicago Communications
• Homeland Security: Plain Language FAQs
• City of Winston-Salem: Radio Codes
• Domestic Preparedness
• Echo911
• (https://www.egovlink.com/public_documents300/waynesville/published_documents/departments/police/ten%20codes.pdf)
• Wikipedia: Radio Telephony Spelling Alphabet
• Federal Communications Commission (FCC)
• Federal Emergency Management Agency (FEMA)
• (https://dms-media.ccplatform.net/content/download/95007/556332/file/SOP%2014%2010-Codes.pdf)
• (https://www.gao.gov/products/gao-18-379)
• (https://georgewbush-whitehouse.archives.gov/reports/katrina-lessons-learned/chapter5.html)
• (https://govinfo.gov/content/pkg/CHRG-109shrg66932/html/CHRG-109shrg66932.htm)
• (https://www.hhs.gov/sites/default/files/2023-plain-writing-complaince-report.pdf)
• Hilaris Publisher
• Effects of Poor Communication in Healthcare
• International Association of Fire Chiefs (IAFC)
• (https://www.k-state.edu/ksuarc/codes.pdf)
• (https://www.lep.gov/sites/lep/files/resources/vera_translating_justice_final.pdf)
• (https://www.marshalsecurity.ca/apco-10-codes/)
• (https://midlandusa.com/blogs/blog/the-quick-guide-to-walkie-talkie-codes)
• (https://www.nj.gov/comptroller/reports/2023/20230503.shtml)
• University of Utah Health
• (https://oig.justice.gov/sites/default/files/archive/special/s0606/chapter6.htm)
• Office of Justice Programs (OJP)
• Performance Protocol
• National Library of Medicine (PMC)
• Police1
• Police Chief Magazine
• Police Forum
• National Policing Institute
• (https://repository.law.miami.edu/cgi/viewcontent.cgi?params=/context/umlr/article/4673/&path_info=UMLR_20vol_2076_20no_202_20447_524_Blasie_Plain_20Language.pdf)
• (https://secure.smore.com/n/d8z4p-police-10-codes)
• 10 Codes: Why They Matter
• (https://www.tandfonline.com/doi/full/10.1080/10410236.2024.2346677)
• (https://www.theiacp.org/topics/data-transparency)
• (https://www.theisrm.org/documents/Garnett%20&%20Kouzmin%20(20007)%20Communicating%20Throughout%20Katrina%20-%20Competing%20and%20Complementary%20Conceptual%20Lenses%20on%20Crisis%20Communication.pdf)
• FEMA Emergency Management Institute
• Tucson Radio Codes
• (https://ucr.fbi.gov/leoka/leoka-2010/aboutucrmain)
• (https://www.volusiasheriff.gov/resources/10-codes-and-signals.stml)
• (https://web.stanford.edu/~reneeb/bill/n.radio.code.html)
• (https://www.zipscanners.com/blogs/learn/police-codes)