Police code 10-20 means “location.” When a dispatcher radios “what’s your 10-20?” they’re asking an officer where they are, and the officer answers with a cross-street, address, or landmark. The phrase spilled out of law enforcement decades ago through CB radio, which is why you’ll still hear civilians ask “what’s your 20?” when they want to know where a friend is.
How 10-20 Works on the Radio
A typical exchange is short. The dispatcher calls a unit number and asks for its 10-20. The officer keys the microphone and gives a position: an intersection, a street address, a mile marker, or a recognizable landmark. If they’re driving, they add direction of travel so dispatch can anticipate where the unit will be in a minute or two.
The code runs both ways. A supervisor can request a 10-20 to check on a unit. An officer can volunteer one to announce arrival on scene, or to flag that they’ve moved. Dispatchers enter each reported position into Computer-Aided Dispatch, which produces a timestamped log of every unit throughout the shift.
Accuracy is the point. A wrong cross-street during an emergency sends backup to the wrong place, and departments treat location awareness as a safety fundamental. Failing to respond to a dispatch inquiry, or giving an inaccurate position, can trigger an internal review.
Where “What’s Your 20?” Came From
Most people searching for 10-20 are not police officers. They’ve heard “what’s your 20?” in a movie, a text, or a conversation and want to know where it originated. Ten-codes migrated from law enforcement into civilian CB radio in the late 1940s. When CB exploded in popularity among truckers in the 1970s and 1980s, “what’s your 20?” moved with it into everyday American slang. It stuck around as a casual, slightly retro way of asking where someone is, even as police radio practice moved on.
A Short History of Ten-Codes
The Association of Police Communications Officers, now APCO International, first proposed brevity codes in the June 1935 issue of its bulletin, adapting U.S. Navy procedure symbols for police use. The more familiar set of APCO 10 Signals followed in 1937, developed largely by Charles Hopper, communications director for the Illinois State Police.1Police1. Police 10 Codes vs. Plain Language: The History and Ongoing Debate
The codes solved a technical problem. Early police radios were slow and unreliable, channels were shared and congested, and compressing common phrases into two- or three-digit numbers meant less airtime and fewer garbled transmissions. The equipment limits are long gone. The habit remains.
Other Ten-Codes You’ll Hear
A handful of ten-codes stayed in common use alongside 10-20 in departments that still rely on them:
- 10-4: Acknowledged or understood. The most famous of the set.
- 10-7: Out of service. An officer signing off or temporarily unavailable.
- 10-8: In service and available for calls.
- 10-21: Call by phone, often for sensitive information.
- 10-28: Vehicle identification check, requesting registration on a plate.
These are not universal. The same number can mean different things in different departments, which turns out to matter when agencies have to work together.
How GPS Changed Location Reporting
Verbal 10-20 reports are now backed up by automation. Most modern patrol vehicles carry Automated Vehicle Location equipment that feeds GPS coordinates straight into the dispatch computer. The CAD system converts those coordinates into a street address and updates the unit’s position in real time, no microphone required.2Bureau of Justice Assistance. Standard Functional Specifications for Law Enforcement Computer Aided Dispatch (CAD) Systems
AVL also helps dispatchers pick which unit to send. Rather than polling three officers for their 10-20 and mentally mapping who is closest, the system calculates proximity automatically. Radios built on the Project 25 standard can transmit GPS data alongside voice, though CISA guidance notes that automated location is less reliable in parking garages, dense urban corridors, and other spots with poor satellite reception.3Cybersecurity & Infrastructure Security Agency. Project 25 (P25)
Verbal reports haven’t gone away. Officers still announce their position when they arrive on scene, during foot pursuits, or any time they leave the vehicle, because the GPS only knows where the car is parked.
Why Some Departments Dropped Ten-Codes
In 2006, the federal government recommended ending ten-codes in favor of plain language. The push came through the National Incident Management System, which required plain language for any multi-agency, multi-jurisdiction event, including major disasters and large-scale exercises. Starting in fiscal year 2006, federal preparedness grant funding was tied to compliance.4Federal Emergency Management Agency. NIMS Alert – NIMS and Use of Plain Language
The reasoning was practical. Ten-codes aren’t standardized across departments. The same number can mean “acknowledged” in one county and something far more serious in the next. When agencies from different jurisdictions converge on a disaster, coded language becomes a hazard. CISA’s plain language guidance stated the problem directly: responders who train in codes revert to codes under stress, and in a mutual aid crisis that miscommunication can cost lives.5Cybersecurity and Infrastructure Security Agency. Plain Language Guide Frequently Asked Questions
The NIMS requirement doesn’t ban ten-codes inside a single department. Agencies that want to keep 10-20 and its companions for routine internal radio traffic are free to do so, and many sheriff’s offices and smaller departments still prefer them for brevity and a degree of privacy from civilian scanners.6Federal Emergency Management Agency. NIMS Alert – Plain Language That’s why 10-20 still turns up on the radio in some jurisdictions and never in others.