As a law-abiding citizen, you probably listen closely when those blue and red lights flash behind you on the highway. And if you‘re like me, you may tune into the local police scanner whenever major news breaks in your city.
But when those cryptic "10 codes" start flying back and forth on the radio, do you really understand everything going on?
As a hobbyist scanner listener and tech writer focused on public safety technology, I‘ve spent years decoding law enforcement communications. And I‘m here to lift the veil of secrecy surrounding police codes and signals.
In this comprehensive guide, I‘ll break down the meaning of common 10 codes and police signals in clear everyday language. I‘ll also share expert insights into police radio culture and the role codes play.
With the knowledge from this guide, you‘ll understand more about officer safety alerts, call priorities, and radio procedures. Let‘s get started unraveling the mystery around 10 codes!
A Brief History of 10 Codes in American Policing
Before diving into code definitions, it helps to understand where 10 codes came from in the first place.
The 10-code system traces back to the 1930s when the Association of Public-Safety Communications Officials (APCO) introduced a set of standardized numeric codes for police radio usage. APCO‘s work was later adopted by the International Association of Chiefs of Police (IACP) as the official 10 code standards.
Under this original system, "10" prefixed all codes, followed by another number from 1 to 99 designating specific meanings. For example, 10-1 meant "Unable to copy/repeat," while 10-97 signified "On scene."
According to radio historians, the "10" prefix was chosen since early radio equipment filtered out lower frequencies. Starting codes with 10- ensured intelligibility.
The use of coded signals enabled officers to communicate discreetly in an era before widespread encryption. Codes also fostered quicker communication on low-bandwidth radio systems.
By the 1960s, the 10-code system grew to over 200 unique signals covering officer status, call priority levels, jurisdictional aid requests, and common situations. However, many codes remained unknown outside of law enforcement.
This cloak of secrecy frustrated journalists and citizen band radio hobbyists seeking to monitor law enforcement activities. The codes prevented straightforward public understanding of radioed events.
The Push Towards Plain English
Seeking improved radio clarity and public accountability, APCO recommended phasing out codes in favor of plain English in the 1970s.
Critics argued codes were an unnecessary barrier on encrypted digital channels. Code variability between agencies also increased the possibility for dangerous misunderstandings.
However, ditching codes entirely faced resistance from the law enforcement community. Officers viewed codes as integral to tradition and culture. Many agencies held the public had no inherent right to hear the details of police communication.
According to a 2013 Police Executive Research Forum survey, only 25% of agencies used plain English while over half continued using modified 10 codes. The remaining agencies used a mix of both.
The survey showed larger metropolitan agencies more frequently embraced plain English due to multijurisdictional interoperability concerns. However, the tradition of 10 codes persists in most regions.
This ongoing tension between the public desire for transparency and law enforcement preference for discretion continues today. However, common codes do provide citizens valuable insight into events when monitored legally.
Decoding the Top 10 Police 10 Codes
While police agencies use hundreds of codes, some 10 codes are near universal due to APCO standardization. I‘ll focus this guide on the most common codes bearing consistent meanings across jurisdictions.
However, always keep in mind a department may alter specific codes based on local needs. Fortunately, broader regional interoperability initiatives are gradually improving standardization.
10-1: Unable to Copy
When an officer says "10-1", it indicates they were unable to hear or understand a radio transmission. The receiving party requests a repetition with "10-1."
Background noise, weak signal strength, or fast speech can all prompt a 10-1 response. Upon hearing 10-1, the sender simply repeats the original transmission.
10-4: Acknowledged
The 10-4 code is likely the most widely recognized, thanks to pop culture references in movies and television. 10-4 acts as a radio signal meaning "message received" or "acknowledged."
Dispatchers frequently use 10-4 to confirm receipt of critical information from field personnel. Officers responding to calls also employ 10-4 to check-in upon arrival at the scene.
10-4 conveys the equivalent of "okay" or "roger that" in casual conversation. After a 10-4, both parties understand the message was properly received.
10-9: Repeat
Similar to 10-1, dispatchers and officers use 10-9 when they need a full repetition of a unclear radio transmission.
Reasons for requesting a 10-9 repeat include:
- Broken up or distorted audio
- Transmission too rapid to comprehend
- Critical details missed
To avoid tying up the radio channel with a full rerun, the receiving party will say "10-9" to obtain just the critical portion again.
10-16: Pick Up Prisoner
When officers make an arrest, they use 10-16 to summon a transport unit to convey the suspect to a detention facility. 10-16 contains key details like the arrest location and prisoner specifics.
An example transmission might be:
"Dispatch from Unit 12, 10-16 male suspect in custody for 148 PC at 24 Main Street."
This alerts dispatch to send a caged transport to pick up the arrested party at the specified site.
10-20: Location
10-20 is one of the oldest known 10 codes, originating back in the very first APCO system. When responding to calls, dispatchers will frequently ask officers "10-20?" to request their current location.
Officers reply with a specific address or nearby landmark. During pursuits, officers also use 10-20 to pinpoint the chase location to guide assisting units.
Providing an accurate 10-20 is crucial for coordinating an effective response to any incident. It keeps the location updated for all personnel.
10-21: Telephone Call
When sensitive information must be conveyed outside radio transmission, dispatchers use 10-21. 10-21 instructs an officer to contact dispatch immediately by telephone.
This may occur when:
- Radio channels are unencrypted
- The information is very lengthy
- Poor radio coverage exists in an area
After receiving a 10-21 prompt, officers proceed to the nearest landline associated with the dispatch center. This allows the dispatcher to provide the confidential details directly over the phone.
10-37: Investigate Suspicious Vehicle
When dispatch receives a report of a suspicious occupied vehicle, they alert field personnel using 10-37. This provides the vehicle description, occupants, and location to investigate.
Upon arrival, the investigating officer approaches with caution since suspicious vehicles may be engaged in criminal activity or contain dangerous persons. Backup units maintain a safe perimeter as warranted.
10-77: Request for Expedited Response
When an incident escalates suddenly, officers request urgent backup with 10-77. This signals a routine call has intensified, requiring additional units to expedite response.
Scenarios where 10-77 may be used include:
- Domestic disturbance has become violent
- Additional weapons spotted at a felony stop
- Chest pains reported at a sick call
Any available personnel in the vicinity immediately respond to the 10-77 call for assistance. Neighboring jurisdictions may also send resources depending on the nature of the emergency.
10-97: On Scene
Dispatchers coordinate response units using the 10-97 code. 10-97 confirms personnel have arrived at the location of a call for service.
After the first officer broadcasts 10-97, dispatch logs the arrival time and notifies other responding units they may slow down or divert to other missions. Arrival updates are critical to maintain real-time tracking of personnel.
Bonus: 10-100
While not strictly a 10 code, 10-100 is a radio signal every citizen and officer urgently listens for. 10-100 indicates an officer is in immediate life-threatening danger.
All nearby units respond on an emergency basis when 10-100 is broadcast, since an officer faces grave harm without immediate assistance. 10-100 mobilizes the maximum possible force to save a downed officer from serious injury or death.
Police Codes for Crimes and Call Types
Beyond 10 codes, police agencies also use codes for common crimes and calls for service. Here are some examples:
- 211: Robbery in progress
- 459: Burglary in progress
- 487: Grand theft auto
- 502: Drunk driver
- 586: Disturbing the peace
- 11-80: Major accident scene
- 11-99: Officer needs assistance
Much like 10 codes, these crime codes paint a quick picture using few words to dispatch the proper response. An observer listening to "487 reported" understands a vehicle theft occurred.
Police Scanner Codes and Signals
In addition to the 10 codes and call type codes above, officers verbally transmit other key information during incidents. Scanner hobbyists keep an ear out for these radio signals indicating significant events:
- Code 3: Lights and siren response to emergency
- Code 4: No further assistance needed
- Shot fired: Gunshot reported on scene
- 11-24: Dead body discovered
- 11-41: Person down requiring medical
- 11-42: Traffic accident with injuries
- 11-99x: Officer in immediate danger
Learning these scanner code meanings helps inform the seriousness levels of unfolding calls. For example, hearing "11-42" alerts you that a significant traffic collision has occurred in the area.
Regional and Local Variations Do Occur
While this guide focused on the standard meanings for common codes, some regional and local differences exist:
- Smaller agencies may still use traditional APCO codes unmodified since the 1930s
- Large metro departments may use completely localized codes
- Neighboring jurisdictions may share codes under mutual aid agreements
- Special operations units may have unique codes
- Encrypted talkgroups may alter codes or use plain English
If you regularly listen to a local police scanner, get a frequency guide or code sheet to understand specialized codes used in that area. Pay attention to how codes are used in context for your city.
With knowledge of the common codes, you‘ll more easily pick up on any local variations. This enhances understanding of the radio chatter.
Are Codes Still Necessary in the Digital Age?
Even with today‘s encrypted digital radio systems, the tradition of 10 codes lives on in most police agencies. But are codes still truly necessary?
Reasons Some Agencies Defend Keeping Codes
- Enables faster communication on a shared channel
- Avoid tying up the channel with lengthy plain English
- Traditional ingroup identity and pride
- Public has no "right" to understand police activities
Arguments for Moving to Plain English
- Code mistakes can lead to critical errors
- Encryption provides sufficient discretion
- Promotes interagency interoperability
- Enhances community understanding and trust
This debate will likely continue, but change happens slowly in law enforcement culture. Both sides offer valid perspectives. My view is a hybrid approach may emerge, with common situations using codes but plain English for complex details.
The public interest merits understandable communications, but officers also deserve efficient systems for their dangerous work. With compromise, both aims can be balanced in our transparent digital age.
Scanner Codes Enhance Understanding of Events
When that Breaking News alert flashes on your phone, there‘s often minimal detail on what‘s unfolding. That‘s where a police scanner becomes an invaluable information source.
By listening to real-time scanner traffic, you gain situational awareness no traditional media outlet can yet provide. The coded signals allow tracking the police response and grasping incident specifics.
As law enforcement communications become more encrypted and inaccessible, radio codes remain one of the last listening windows available to engaged citizens. That transparency strengthens community trust and accountability.
So now that you‘re familiar with common 10 codes and signals, I hope you feel empowered to tune in and better comprehend the scanner chatter. With this guide‘s help, the secret language of police radio won‘t sound so mysterious anymore!
Stay safe out there,
Terry W.
