Police 10 Codes: The Complete Guide to Law Enforcement Radio Codes
Everything you need to know about police radio codes, from “10-4” to specialized signals used by departments across America.
Police 10 codes are brevity codes used by law enforcement to communicate quickly and efficiently over radio. Each code starts with “10” followed by a number that represents a specific message. For example, 10-4 means “acknowledged” or “message received,” while 10-20 means “location” (as in “what’s your 10-20?”).
These codes were developed in 1937 to save airtime on limited radio channels and have since become deeply embedded in law enforcement culture, though many departments now use plain language for better inter-agency communication.
Table of Contents
What Are Police 10 Codes?
Police 10 codes (also written as “ten codes” or “10-codes”) are a system of numeric codes used by law enforcement officers to communicate via radio. Each code begins with the number “10” followed by another number, creating a standardized shorthand for common phrases and situations.
When an officer says “10-4,” they’re acknowledging receipt of a message. When dispatch asks for a “10-20,” they want to know an officer’s location. These codes allow officers to convey complex information in just a few syllables, which was crucial in the early days of radio when channel capacity was limited.
The codes serve several purposes beyond brevity. They provide a degree of privacy from civilians monitoring police scanners, they reduce the chance of miscommunication caused by static or interference, and they’ve become a deeply ingrained part of police culture and identity.
The History of Police 10 Codes
The 10-code system was developed between 1937 and 1940 by Charles “Charlie” Hopper, the communications director for the Illinois State Police. Working with the Association of Public-Safety Communications Officials (APCO), Hopper created the codes to address a practical problem with early radio technology.
In those days, radio transmitters needed a moment to reach full power after the microphone button was pressed. If an officer started speaking immediately, the first syllable would often be cut off. By prefixing every code with “ten,” officers gave their radios time to warm up while still transmitting useful information.
The word “ten” served as a verbal primer, giving early vacuum-tube radios the split-second they needed to reach full transmission power. Without this prefix, crucial first words would be lost to static. This technical necessity became a lasting tradition.
APCO published its first official list of 10-codes in January 1940. The system was revised in 1955 based on an analysis by the San Diego Police Department, and again in 1974 as part of APCO Project 14. These revisions attempted to standardize meanings across jurisdictions, though local variations persisted.
The codes entered popular culture through the 1950s television series “Highway Patrol” starring Broderick Crawford, whose frequent use of “10-4” made the phrase widely recognized. CB radio enthusiasts adopted the codes in the 1970s, further cementing phrases like “10-4, good buddy” in American vernacular.
Today, police officers, sheriff’s deputies, and state troopers across America still use variations of these codes, though a growing number of departments have transitioned to plain language for improved inter-agency communication.
Complete Police 10-Code List (APCO Standard)
Below is the complete list of standard APCO 10-codes. Keep in mind that meanings can vary by department and jurisdiction. The codes below represent the most widely accepted definitions.
These codes are not universal. A 10-32 in Texas may mean something completely different in Georgia. Always verify with your local department if you need accurate information for your jurisdiction.
| Code | Meaning |
|---|---|
| 10-0 | Caution |
| 10-1 | Unable to copy / Poor reception |
| 10-2 | Signal good / Receiving well |
| 10-3 | Stop transmitting |
| 10-4 ⭐ | Acknowledgment / OK / Message received |
| 10-5 | Relay message |
| 10-6 | Busy / Stand by unless urgent |
| 10-7 ⭐ | Out of service |
| 10-8 | In service / Available for assignment |
| 10-9 | Repeat message / Say again |
| 10-10 | Negative / Fight in progress (varies) |
| 10-11 | Dog case / Animal problem |
| 10-12 | Stand by / Visitors present |
| 10-13 | Weather and road conditions |
| 10-14 | Prowler report / Suspicious person |
| 10-15 | Prisoner in custody |
| 10-16 | Domestic disturbance |
| 10-17 | Meet complainant |
| 10-18 | Complete assignment quickly |
| 10-19 | Return to station |
| 10-20 ⭐ | Location / “What’s your 10-20?” |
| 10-21 | Call by telephone |
| 10-22 | Disregard / Cancel |
| 10-23 | Arrived at scene |
| 10-24 | Assignment completed |
| 10-25 | Report in person / Meet… |
| 10-26 | Detaining subject / ETA |
| 10-27 | Driver’s license information |
| 10-28 | Vehicle registration information |
| 10-29 | Check for wanted / NCIC check |
| 10-30 | Unnecessary use of radio / Does not conform to rules |
| 10-31 | Crime in progress |
| 10-32 ⭐ | Person with gun |
| 10-33 | Emergency / All units stand by |
| 10-34 | Riot / Major disturbance |
| 10-35 | Major crime alert |
| 10-36 | Correct time |
| 10-37 | Investigate suspicious vehicle |
| 10-38 | Stopping suspicious vehicle |
| 10-39 | Urgent / Use lights and siren |
| 10-40 | Silent run / No lights or siren |
| 10-41 | Beginning tour of duty |
| 10-42 ⭐ | Ending tour of duty (Also used ceremonially for officer deaths) |
| 10-43 | Information |
| 10-44 | Permission to leave |
| 10-45 | Dead animal / Deceased person (varies) |
| 10-46 | Assist motorist |
| 10-47 | Emergency road repairs needed |
| 10-48 | Traffic standard needs repair |
| 10-49 | Traffic light out |
| 10-50 | Accident / Traffic collision |
| 10-51 | Wrecker needed |
| 10-52 | Ambulance needed |
| 10-53 | Road blocked |
| 10-54 | Livestock on highway |
| 10-55 | Intoxicated driver |
| 10-56 | Intoxicated pedestrian |
| 10-57 | Hit and run |
| 10-58 | Direct traffic |
| 10-59 | Convoy or escort |
| 10-60 | Squad in vicinity |
| 10-61 | Personnel in area |
| 10-62 | Reply to message |
| 10-63 | Prepare to copy |
| 10-64 | Message for local delivery |
| 10-65 | Net message assignment |
| 10-66 | Message cancellation |
| 10-67 | Clear to read net message |
| 10-68 | Dispatch information |
| 10-69 | Message received |
| 10-70 | Fire alarm |
| 10-71 | Advise nature of fire |
| 10-72 | Report progress on fire |
| 10-73 | Smoke report |
| 10-74 | Negative |
| 10-75 | In contact with… |
| 10-76 | En route to… |
| 10-77 | ETA (Estimated Time of Arrival) |
| 10-78 | Need assistance |
| 10-79 | Notify coroner |
| 10-80 | Chase in progress |
| 10-81 | Breathalyzer report |
| 10-82 | Reserve lodging |
| 10-83 | Work school crossing |
| 10-84 | If meeting, advise ETA |
| 10-85 | Delayed due to… |
| 10-86 | Officer on duty |
| 10-87 | Pick up checks for distribution |
| 10-88 | Present telephone number of… |
| 10-89 | Bomb threat |
| 10-90 | Bank alarm |
| 10-91 | Pick up prisoner |
| 10-92 | Improperly parked vehicle |
| 10-93 | Blockade |
| 10-94 | Drag racing |
| 10-95 | Prisoner in custody |
| 10-96 | Mental subject / Psych patient |
| 10-97 | Check signal / Arrived at scene |
| 10-98 | Prison break / Jail escape |
| 10-99 ⭐ | Officer needs help / Emergency (Also: Wanted/stolen indicated) |
- 18,000+ law enforcement agencies in the United States
- 100+ different 10-code variations documented
- 1937 – Year the 10-code system was first developed
- 19 states had switched to plain language by 2009
Most Common Police Codes Explained
While there are nearly 100 standard 10-codes, most daily police communication relies on a handful of frequently used codes. Here’s an in-depth look at the codes you’re most likely to hear:
10-4: Acknowledgment / OK
By far the most famous police code, 10-4 simply means “acknowledged” or “message received and understood.” When dispatch gives an officer instructions and they respond with “10-4,” they’re confirming they heard and understood the message.
This code became so popular through television and CB radio culture that it’s now used colloquially by the general public. You might hear someone say “10-4” in everyday conversation to mean “got it” or “understood.”
10-20: Location
10-20 refers to location. When someone asks “What’s your 10-20?” they’re asking “Where are you?” Officers use this to report their current position or to ask dispatch or other units where they are.
Like 10-4, this code has crossed into popular culture. Truckers and CB radio enthusiasts commonly use “What’s your 20?” to ask about someone’s location.
10-7 and 10-8: Out of Service / In Service
10-7 means an officer is out of service and unavailable for calls. This could be for a meal break, end of shift, or any other reason they can’t respond to incidents.
10-8 is the opposite, indicating the officer is back in service and available for assignments. These codes help dispatch know which units are available at any given time.
When a police officer retires or passes away, a ceremonial “final 10-42” is often broadcast. Dispatch will call the officer’s badge number and announce they are “10-7 for the last time” and then “10-42, end of watch.” This tradition honors their service and formally marks their departure from duty.
10-99: Officer Needs Help
One of the most urgent codes, 10-99 signals that an officer needs immediate assistance. In some jurisdictions, this specifically means an officer is in danger. When this code is broadcast, all available units typically respond.
Note: In some areas, 10-99 means “wanted or stolen indicated” (referring to a vehicle or person check), so context and local variation matter significantly.
10-33: Emergency
10-33 indicates an emergency requiring all other units to stand by and clear the channel. When this code is called, non-essential radio traffic stops immediately to allow emergency communication to flow uninterrupted.
California 11-Codes
California law enforcement agencies, particularly the California Highway Patrol (CHP), use an additional set of “11-codes” alongside standard 10-codes. These codes address situations specific to traffic enforcement and California law.
| Code | Meaning |
|---|---|
| 11-10 | Take a report |
| 11-24 | Abandoned vehicle |
| 11-25 | Traffic hazard |
| 11-41 | Ambulance needed |
| 11-42 | No ambulance needed |
| 11-44 | Coroner case (deceased person) |
| 11-48 | Provide transportation |
| 11-54 | Suspicious vehicle |
| 11-80 | Major accident – Loss of life |
| 11-81 | Minor accident – No injuries |
| 11-82 | Accident – Injury |
| 11-83 | Accident – No details |
| 11-85 | Tow truck needed |
| 11-99 | Officer needs help – EMERGENCY |
Police Signal Codes
In addition to 10-codes and 11-codes, many departments use “signal codes” – single or double-digit numbers without a prefix that indicate specific situations. These are often used in the Southeast United States.
| Signal | Meaning |
|---|---|
| Signal 0 | Graveyard dead / Obviously deceased |
| Signal 1 | Call your station |
| Signal 4 | No further assistance needed |
| Signal 7 | Out for investigation |
| Signal 13 | Major disaster activation |
| Signal 20 | Officer needs immediate assistance |
| Signal 30 | Homicide |
| Signal 36 | Shooting / Shots fired |
| Signal 63 | Prepare to copy information |
Response Codes (Code 1, 2, 3)
These codes indicate how quickly an officer should respond to a call:
- Code 1: Respond at your convenience – non-urgent call
- Code 2: Urgent response – respond quickly but no lights/siren
- Code 3: Emergency response – lights and siren, immediate response required
- Code 4: No further assistance needed – situation under control
- Code 5: Stakeout in progress – stay away
- Code 6: Out for investigation
- Code 7: Mealtime / Taking a break
Police Phonetic Alphabet (NATO/ICAO)
When spelling out names, license plates, or other information over the radio, officers use the NATO phonetic alphabet to ensure clarity. This prevents confusion between similar-sounding letters like “B” and “D” or “M” and “N.”
Some older departments may still use the LAPD/APCO phonetic alphabet, which uses names instead: Adam, Boy, Charles, David, Edward, Frank, George, Henry, Ida, John, King, Lincoln, Mary, Nora, Ocean, Paul, Queen, Robert, Sam, Tom, Union, Victor, William, X-ray, Young, Zebra.
Why Police Codes Vary by Department
One of the most confusing aspects of police codes is that they’re not universal. A 10-32 might mean “person with gun” in one jurisdiction and “backup required” in another. This variation exists for several reasons:
Historical Development
When APCO published its original codes in 1940, adoption was voluntary. Many departments had already developed their own systems or modified the APCO codes to better fit their local needs. These modifications became entrenched over decades of use.
Local Needs
A rural sheriff’s department in Wyoming has different communication needs than the NYPD. Coastal departments might need codes for maritime incidents, while departments in agricultural areas might need livestock-related codes. Local adaptation made practical sense.
No Central Authority
Unlike the military, there’s no central authority mandating that all police departments use identical codes. Each of the approximately 18,000 law enforcement agencies in the United States operates somewhat independently, leading to a patchwork of code systems.
During Hurricane Katrina rescue operations in 2005, the lack of standardized codes created dangerous communication breakdowns. Officers from different jurisdictions couldn’t understand each other’s radio traffic. A 10-code that meant “lunch break” in one department meant “emergency” in another. This disaster directly led to federal recommendations to abandon 10-codes in favor of plain language.
The Shift to Plain Language
Following the communication failures during Hurricane Katrina, the U.S. Department of Homeland Security and FEMA began strongly recommending that emergency services adopt “plain language” communication instead of coded systems.
In 2006, the National Incident Management System (NIMS) formally recommended against using 10-codes for inter-agency communication. The argument was straightforward: when lives are on the line, there’s no room for misinterpretation.
Arguments For Plain Language
- Universal Understanding: “Officer down” means the same thing everywhere
- Inter-agency Cooperation: Critical during disasters, pursuits across jurisdictions, and mutual aid
- Reduced Training Time: New officers don’t need to memorize extensive code lists
- Public Safety: Civilian witnesses can understand and provide better information
Arguments For Keeping Codes
- Brevity: “10-4” is faster than “message received and understood”
- Tradition: Codes are deeply embedded in police culture and identity
- Tactical Privacy: Codes provide some obscurity from scanner listeners (though this is largely a myth, as code lists are widely published)
- Muscle Memory: Veteran officers have decades of ingrained habits
By 2011, approximately 19 states had officially transitioned to plain language, though adoption remains uneven. Many departments now use a hybrid approach: plain language for complex situations and inter-agency communication, but familiar codes like 10-4 for routine acknowledgments.
Some argue that codes keep communications private from scanner listeners. In reality, code lists have been published online for decades, and anyone with a police scanner app can easily look up meanings. True communication security comes from encrypted digital radio systems, not obscure codes.
Frequently Asked Questions About Police 10 Codes
- 10-4 (acknowledged) and 10-20 (location) are the most universally recognized police codes
- Police codes were developed in 1937 to accommodate early radio technology limitations
- Codes are NOT universal – meanings vary significantly between jurisdictions
- Following Hurricane Katrina, federal agencies recommended switching to plain language
- Many departments now use a hybrid approach: codes for routine communication, plain language for complex situations
- The 10-42 (end of watch) tradition remains a solemn way to honor officers
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