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Ten-codes, officially known as ten signals, are brevity codes used to represent common phrases in voice communication, particularly by law enforcement and in Citizens Band (CB) radio transmissions.

The codes, developed in 1937 and expanded in 1974 by the Association of Public-Safety Communications Officials-International (APCO), allow brevity and standardization of message traffic. They have historically been widely used by law enforcement officers in North America, but, due to the lack of standardization, in 2006 the U.S. federal government recommended they be discontinued in favor of everyday language.[1]


APCO first proposed Morse code brevity codes in the June 1935 issue of The APCO Bulletin, which were adapted from the procedure symbols of the U.S. Navy.[2]

The development of the APCO Ten Signals began in 1937 to reduce use of speech on the radio at a time when police radio channels were limited. Credit for inventing the codes goes to Charles "Charlie" Hopper, communications director for the Illinois State Police, District 10 in Pesotum, Illinois. Hopper had been involved in radio for years and realized there was a need to abbreviate transmissions on State Police bands.[3] Experienced radio operators knew the first syllable of a transmission was frequently not understood because of quirks in early electronics technology. Radios in the 1930s were based on vacuum tubes powered by a small motor-generator called a dynamotor. The dynamotor took from 1/10 to 1/4 of a second to "spin up" to full power. Police officers were trained to push the microphone button, then pause briefly before speaking; however, sometimes they would forget to wait. Preceding each code with "ten-" gave the radio transmitter time to reach full power. An APCO Bulletin of January 1940 lists codes assigned as part of standardization;[4]

The Ten Signals were included in APCO Project Two (1967), "Public Safety Standard Operating Procedures Manual", published as study cards in APCO Project 4 (1973), "Ten Signal Cards", and then revised in APCO Project 14 (1974).[5][6][7][8]

In popular culture[edit]

Ten-codes, especially "10-4" (meaning "understood") first reached public recognition in the mid- to late-1950s through the popular television series Highway Patrol, with Broderick Crawford. Crawford would reach into his patrol car to use the microphone to answer a call and precede his response with "10-4".

Ten-codes were adapted for use by CB radio enthusiasts. C. W. McCall's hit song "Convoy" (1975), depicting conversation among CB-communicating truckers, put phrases like 10-4 and what's your twenty? (10-20 for "where are you?") into common use in American English.

The movie Convoy (1978), loosely based on McCall's song, further entrenched ten-codes in casual conversation.

Replacement with plain language[edit]

While ten-codes were intended to be a terse, concise, and standardized system, the proliferation of different meanings can render them useless in situations when officers from different agencies and jurisdictions need to communicate.

In the fall of 2005, responding to inter-organizational communication problems during the rescue operations after Hurricane Katrina, the United States Federal Emergency Management Agency (FEMA) discouraged the use of ten-codes and other codes due to their wide variation in meaning.[9][10] The Department of Homeland Security's SAFECOM program, established in response to communication problems experienced during the September 11 attacks also advises local agencies on how and why to transition to plain language,[11] and their use is expressly forbidden in the nationally standardized Incident Command System, as is the use of other codes.[12]

APCO International's current position states that plain speech communications over public safety radio systems is preferred over the traditional 10-Codes and dispatch signals,[13] As of 2011, ten-codes remain in common use in many areas, but are increasingly being phased out in favor of plain language,[1] with nineteen states planning to change to plain English as of the end of 2009.[14]

Examples of ten-codes[edit]

Some examples of the codes are:[15]

  • 10-1 Bad reception
  • 10-4 I acknowledge/Affirmative/Copy
  • 10-9 Say again
  • 10-20 Advise to location
  • 10-21 Call
  • 10-33 Emergency: all units stand by
  • 10-36 Correct time

Many additional codes have been added by individual local or regional first-response agencies; these are not standard across jurisdictions and may be problematic if multiple organizations must respond to the same incident.

Related codes[edit]

  • The California Highway Patrol uses ten-codes, along with an additional set of eleven- and higher codes.[16]
  • California Penal Code sections were in use by the Los Angeles Police Department as early as the 1940s, and these Hundred Code numbers are still used today instead of the corresponding ten-code. Generally these are given as two sets of numbers[citation needed]—"One Eighty-Seven" or "Fifty-One Fifty"—with a few exceptions such as "459"—Burglary, which is given as "Four-Five-Nine". The American public was made aware of these California Penal Code references as a result of the TV series Adam-12, which used them habitually in radio communications and in the main title of the show. The best-known include:
    • "187": Homicide
    • "211": Robbery
    • "415": Disturbance
    • "417": Person with a weapon
    • "502": Intoxicated Driver
    • "5150": Mentally disturbed person (actually a reference to the California Welfare and Institutions Code)
  • The New York Fire Department uses its own ten-code system.[17]
  • The New Zealand Fire Service uses a system of "K-codes" to pass fire appliance availability statuses as well as operational messages. For example, "K1" means "proceeding to incident", while "K99" means "Structure fire, well involved".[18][19] The New Zealand Police also use some K-codes,[20] with completely unrelated meanings to those used by NZFS; Police code "K1" means "no further police action required".
  • Telegraph and teletype procedures
    • Q code and prosigns for Morse code are used in amateur radio, aviation and marine radio. They provide specific abbreviations for concepts related to aviation, shipping, RTTY, radiotelegraph and amateur radio.[21] In radiotelegraph operation, a Q code is often shorter (as ten-codes require transmission of three prefix characters: 1, 0, hyphen) and provides standardization of codes, essential in international and shortwave communications.
    • Z codes are used by NATO countries in military radio communications.

See also[edit]


  1. ^ a b Heard on Morning Edition (2009-10-13). "Plain Talk Eases Police Radio Codes Off The Air". NPR. Archived from the original on 2009-10-17. Retrieved 2010-01-23. 
  2. ^ "The APCO Bulletin (June 1935)" (PDF). Archived (PDF) from the original on 16 March 2016. Retrieved 15 March 2016. 
  3. ^ James Careless (August 2006). "The End of 10-Codes?". Archived from the original on 16 March 2016. Retrieved 15 March 2016. 
  4. ^ http://28011b0082f55a9e1ec0-aecfa82ae628504f4b1d229bd9030ae1.r13.cf1.rackcdn.com/1940-01-p008-200.pdf Archived 2017-08-10 at the Wayback Machine., p.8
  5. ^ "The Origin of The Ten Code". Archived from the original on 18 June 2015. Retrieved 27 April 2015. 
  6. ^ "APCO Projects". Archived from the original on 18 June 2015. Retrieved 27 April 2015. 
  7. ^ 9-Code, 10-Code. Archived 2015-03-20 at the Wayback Machine. Dispatch Magazine online.
  8. ^ "Official Ten-Code List Association of Public Communications Officers (APCO)". Archived from the original on 2007-10-13. 
  9. ^ The End of the Ten-Code? Archived 2009-07-22 at the Wayback Machine.. Tim Dees, Officer.com, 9 November 2005
  10. ^ 10-4 no more?. Megan Scott, asap (AP), 23 November 2005
  11. ^ "Plain Language Guide" (PDF). SAFECOM program. Department of Homeland Security. Archived from the original (PDF) on 2010-05-27. Retrieved 2010-01-23. 
  12. ^ Federal Emergency Management Agency. NIMS Frequently Asked Questions. Retrieved on 2014-12-01 from "Archived copy". Archived from the original on 2014-12-23. Retrieved 2014-12-02. .
  13. ^ APCO position statement on Plain Speech in Public Safety Communications Archived 2012-05-09 at the Wayback Machine.
  14. ^ Mack, Sharon Kiley (January 1, 2010). "Maine police dropping 10-code, switching to plain language". Bangor Daily News. Archived from the original on January 18, 2012. Retrieved October 26, 2011. 
  15. ^ "Association of Public Communications(APCO) 10 Codes". Archived from the original on 2013-10-04. 
  16. ^ "CHP Glossary". California Highway Patrol. Archived from the original on 2015-11-26. Retrieved 2015-11-25. 
  17. ^ F.D.N.Y. Radio Codes Archived 2010-09-15 at the Wayback Machine. The Unofficial Home Page of FDNY.
  18. ^ "K-Codes" Archived 2016-05-10 at the Wayback Machine.
  19. ^ "Fire radio codes Archived 2016-04-19 at the Wayback Machine.
  20. ^ "Police K code". Radio Wiki. 2012-06-07. Archived from the original on 2013-02-07. 
  21. ^ "Q Codes" (PDF). CB Radio Source. Retrieved 2010-01-23. 

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