Once you start using two-way radios, you quickly realize that mastering the equipment isn’t enough: there’s radio lingo to remember, too, 
including 10 codes and various versions of the phonetic alphabet.
Like the police phonetic alphabet, military phonetic alphabet and radio-specific terms, the codes were developed to help radio users communicate quickly and concisely under tough conditions.
To help you get started on your journey of learning radio lingo, here’s a look at the most common 10 codes and what they mean.
Code History
10 codes – also written ten codes – are essentially short sequences that translate into a longer meaning. The codes can trace their origin to Illinois law enforcement in the 1930s.
Charles Hopper was communications director for the Illinois State Police at the time, and he’s credited with creating the codes to deal with a potentially dangerous radio problem. There was a delay between the time an officer pressed the button to talk and when the transmission of their voice would begin, and if they didn’t remember to pause, operators would miss the beginning of messages.
To make time to cover the delay, Hopper added "10" before the codes so that a full but abbreviated message gets across every time.
Today, the use of the codes has expanded beyond just law enforcement, and they’re used by a variety of public and private industries, including education, transportation – think CB radio lingo – and more. The meanings vary by context, and for our purposes, we’ll deal specifically with the codes standardized by the Association of Police Communications Officers (APCO).
Most Common Codes
Thanks to popular movies and TV shows, the best-known code is "10-4," which means something along the lines of "OK" or "I Understand." But most people who are familiar with the phrase probably didn’t realize that there are dozens of other similar abbreviations that each have their own meaning.
Here are some of the most common codes standardized by APCO:
- 10-1: Bad reception/Signal weak
- 10-9: Say again, or repeat, please
- 10-20: Advise to Location
- 10-36: Current time
- 10-69: Message received
- 10-77: Estimated time of arrival
Eliminating Codes at the Federal Level
Given the inconsistencies in what codes mean across different departments, geographies and industries, some officials say that ten-codes are a thing of the past, and there has been a consistent push at the federal level to discontinue their use.
Detractors of 10 codes point to miscommunications and coordination issues during the response to large-scale disasters such as Hurricane Katrina in 2005. The following year, the National Incident Management System, which is part of the Federal Emergency Management Agency (FEMA), issued guidelines to stop the use of the codes in any multi-agency, multi-jurisdiction and multi-discipline response operation, such as disasters and exercises.
Instead, first responders and others are directed to use “Plain Talk” during radio communications to ensure interoperability and clarity.
Code Defenders
At the local law enforcement level, however, the codes are still very much a part of police radio communications, and many jurisdictions have their own variations that are specific to their departments.
Defenders of the codes say that while two-way radio technology has significantly improved since the codes were invented, there is still a need for brevity over radio communications, and the codes are an important tool. There are also those who say the codes offer discretion to departments as they hold radio conversations that can be monitored.
Beyond their utility, the codes are also part of law enforcement culture and history. By providing a common language within a department, they add to the sense of community and as a link to the past.
