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Ten-codes, properly known as ten signals, are code words 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 for brevity and standardization of message traffic. They have historically been widely used by law enforcement officers in North America, although in 2005, the U.S. federal government recommended they be discontinued in favor of everyday language.



The development of the 10-codes began in 1937, at a time when police radio channels were limited, to reduce use of speech on the radio. Credit for inventing the codes goes to Charles "Charlie" Hopper. He was the Communications Director at the Illinois State Police, District 10, located in Pesotum, Illinois. Hopper was involved in radio for many years and saw a need to abbreviate radio transmissions on State Police bands.[1] Experienced radio operators know that the first syllable of a transmission is frequently not going to be understood, but is a necessary part of "tuning in"; hence preceding every code with "ten" allows a better chance of understanding the critical portion. Also the radios of the day were based on vacuum tubes, with a small motor-generator, called a dynamotor, used to generate the high voltage (300–600 volts, depending on the type of radio) needed to operate the transmitter, and the dynamotor took 1/10 to 1/4 of a second to "spin up". The officers were trained to push the microphone button, and wait a moment, then talk, but sometimes they would forget and preceding every code with "ten-" gave the radio transmitter time to come up to full power.

Ten-codes were later adapted for use by CB radio enthusiasts before its pop culture explosion in the late 1970s. The tremendous popularity of the 1975 Convoy song by C.W. McCall depicting droll conversation among CB-communicating truckers put several phrases, such as 10-4 for "understood" and what's your twenty? (10-20) for "where are you?" into common and enduring use in American English. The song was followed by a 1978 movie Convoy which further entrenched the use of ten-codes in casual conversation.

Replacement with plain language

As of 2010, ten-codes remain in common use, but have been phased out in some areas in favor of plain language.[2] Nineteen states were planning to change to plain English as of the end of 2009.[3]

Codes are often used inefficiently. For instance, an exchange which might be "1 Mike 1, 10-20?" "First and Main" will actually be more like "1 Mike 1, what's your 10-20?" "My 20 is First and Main" – it would be more efficient to simply ask "1 Mike 1, where are you?" "I'm at First and Main." On the other hand, there are times when the use of codes is considered appropriate, even if less efficient than speaking "in the clear." For instance, using discreet codes for sexual assault, homicide, suicide and other such situations can prevent the victim and family from having to hear the description being broadcast to all within earshot. Even when the meaning is known, it is less of an emotional jolt to hear a set of numbers being rattled off than to hear the word for the crime.

While ten-codes were intended to be a terse, concise, and standardized system, the proliferation of different meanings may render them useless in situations where people from different agencies and jurisdictions need to communicate. For that reason their use is expressly forbidden in the nationally-standardized Incident Command System as is the use of other codes.[4]

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 high variability in meaning[5][6] 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.[7] The New Orleans Police Department continued using 10-codes as of 2010.[8] One solution to the inter-jurisdictional problem would be to establish a universal standard for the most common 10-codes, and disallow in ICS situations any other codes.[9]

Related codes

In addition, many agencies mingle various codes, especially those which were using radio dispatch before the ten-codes were developed. For instance, the Los Angeles Police Department, which pioneered law enforcement radio communications[citation needed], largely set the standard for law enforcement communications in California. Dispatchers began using California Penal Code sections in their broadcasts in the 1940s, and these code numbers are still used today, instead of the corresponding ten-code. The best-known include "187" – Homicide, "211" – Armed Robbery, "415" – Disturbance, "417" – Man or woman with a gun, "502" – Intoxicated Driver, "5150" – Mentally Ill Person. Generally these are given as two sets of numbers – "One Eighty-Seven" or "Fifty-One Fifty" – with a few exceptions such as "459" – Burglary, which is given as "Four-Five-Nine." The well-known "420" for marijuana, however, originates from neither.[10]

The California Highway Patrol uses eleven-codes, and the Port Authority Police uses eight codes as part of their communication.

Ten-codes are generally avoided in services such as amateur radio where other existing standards (Q code and prosigns for Morse code) are already long established. Aviation and marine radio is better served by Q-code, as the ten-code phrase lists were designed primarily for local police tasks while Q-code provides specific abbreviations for concepts related to aviation, shipping, RTTY, radiotelegraph and amateur radio.[11] 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 communication.


During the 1970s, some truck drivers and CB radio hobbyists responded to the increased use of ten-codes by the general public by inventing parodies of the ten-code with strictly humorous meanings. The best known were the 13-code[12] and the 18-code.[13]

See also


  1. ^ James Careless (August 2006). "The End of 10-Codes?". Retrieved 2006-10-11. 
  2. ^ Heard on Morning Edition (2009-10-13). "Plain Talk Eases Police Radio Codes Off The Air". NPR. Retrieved 2010-01-23. 
  3. ^ 10-4 No More? Cops Drop Communication Codes
  4. ^ Federal Emergency Management Agency. Frequently Asked Questions - Compliance: NIMS Compliance - Overview Accessed: 05/08/2008 "Q: Our 911 center, which receives and dispatches emergency and non-emergency calls, has told us that we may not use 10-codes at all. I gather we must use plain language when using NIMS ICS. Is that correct? A: Yes, when engaged in incident response using ICS, plain language is required. The value of using 10-codes for simplicity and speed is lost when members of the response team are unaware of their meanings, as may occur in a multi-jurisdiction / multi-agency response event. As 10-codes used in one jurisdiction, or agency, are not the same as those used in another, it is important that responders and incident managers use common terminology to prevent misunderstanding in an emergency situation. While plain English is not required for internal operations, it is encouraged over 10-codes to promote familiarity within operational procedures used in emergencies."
  5. ^ The End of the Ten-Code? – By Tim Dees,, 9 November 2005
  6. ^ 10-4 no more? — By Megan Scott, asap (AP), 25 November 2005
  7. ^ "Plain Language Guide". SAFECOM program. Department of Homeland Security. Retrieved 2010-01-23. 
  8. ^ New Orleans Police Department and Metro Area Live Audio Feed retrieved 25 February 2010
  9. ^ Feds working to end use of 10-codes
  10. ^ "420". Retrieved 2010-01-23. 
  11. ^ "Q Codes". Portland Amateur Radio Club. Retrieved 2010-01-23. 
  12. ^ Colin K McCord (2001-09-21). "CB Radio - 13 Codes". Retrieved 2010-01-23. 
  13. ^ "Computer Tech - Code 18". 

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