Ten-code

Ten-codes, officially known as ten signals, are brevity codes used to represent common phrases in voice communication, particularly by US public safety officials and in citizens band radio transmissions. The police version of ten-codes is officially known as the APCO Project 14 Aural Brevity Code.
The codes, developed during 1937–1940 and expanded in 1974 by the Association of Public-Safety Communications Officials-International, allow brevity and standardization of message traffic. They have historically been widely used by law enforcement officers in North America, but in 2006, due to the lack of standardization, the U.S. federal government recommended they be discontinued in favor of everyday language.

History

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, though these procedures were for communications in Morse code, not voice.
In August 1935, the APCO Bulletin published a recommendation that the organization issue a handbook that described standard operating procedures, including:

A standard message form for use by all police departments.
A simple code for service dispatches relating to corrections, repetitions, etc.
A standard arrangement of the context of messages,.
A standard record system for logging the operation of the station.
Other important records in accordance with the uniform crime reporting system sponsored by the International Association of Chiefs of Police.

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. 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 standardisation.
In 1954, APCO published an article describing a proposed simplification of the code, based on an analysis conducted by the San Diego Police Department. In the September 1955 issue of the APCO Bulletin, a revision of the Ten-Signals was proposed, and it was later adopted.
The Ten Signals were included in APCO Project Two, "Public Safety Standard Operating Procedures Manual", published as study cards in APCO Project 4, "Ten Signal Cards", and then revised in APCO Project 14.

In popular culture

Ten-codes, especially "10-4" first reached public recognition in the mid- to late-1950s through the television series Highway Patrol, with Broderick Crawford.
Ten-codes were adapted for use by CB radio enthusiasts. C. W. McCall's hit song "Convoy", depicting conversation among CB-communicating truckers, put phrases like "10-4" and "what's your twenty?" into common use in American English.
The movie Convoy, loosely based on McCall's song, further entrenched ten-codes in casual conversation, as did the movie Smokey and the Bandit.
The New Zealand reality television show Ten 7 Aotearoa takes its name from the New Zealand Police ten-code 10-7, which means "Unit has arrived at job".

Police officer retirement (North America)

Often when an officer retires, a call to dispatch is made. The officer gives a 10-7 code and then a 10-42 code.

Signals by time period (North America)

Usage by Areas

New Zealand

The New Zealand Police use a variety of radio communication codes including its own version of 10-codes seen below.

Code	Meaning	Activity
10-0	Off duty	In use
10-1	Broadcast to all units	In use
10-2	Enroute to job/event	In use
10-3	Available	In use
10-4	Repeat your last message	In use
10-5	Out of service for a short time	Not in use
10-6	Change radio channel	In use
10-8	Arrived at job/event	In use
10-9	Busy but Available	In use
10-10	Officer requires immediate assistance	In use

Philippines

TxtFire Philippines Fire-Specific 10-Codes

TxtFire Philippines employs a subset of its standard 10-codes exclusively for fire-response operations. These fire-specific signals are used to dispatch and coordinate firefighting resources on VHF/UHF radio.

Fire-specific code list

Fire response protocols

Codes 10-70 through 10-73 automatically trigger dispatch of firefighting units and apparatus.
Code 10-45 is used to identify any fire-service vehicle on the air.
All fire-specific traffic takes priority over routine and non-fire messages on the main frequency.
Operational procedures

Emergency protocols

Codes 10-70 through 10-73 are designated as fire-specific codes that trigger automatic dispatch protocols within the TxtFire network.
Code 10-33 is reserved exclusively for life-threatening emergencies, requiring all non-essential radio traffic to cease immediately.

Communication guidelines

Before initiating non-emergency communication with another station, operators must first request permission using code "10-75" from base control and complete the communication within three minutes, or transfer to a secondary channel.
During curfew hours, only emergency traffic is permitted on the main frequency; routine communications are prohibited.
Base control strictly prohibits vulgar language and commercial or personal advertisements on all frequencies.

Replacement with plain language

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 discouraged the use of ten-codes and other codes due to their wide variation in meaning. 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, and their use is expressly forbidden in the nationally standardized Incident Command System, as is the use of other codes.
APCO International stated in 2012 that plain speech communications over public safety radio systems is preferred over the traditional 10-Codes and dispatch signals. Nineteen states had changed to plain English by the end of 2009., ten-codes remained in common use in many areas, but were increasingly being phased out in favor of plain language.

Phrase Word Brevity Code

About 1979, APCO created the Phrase Word Brevity Code as a direct replacement for the Ten-code.

Phrase word	English meaning	APCO Ten-code
Use Caution	Caution: dangerous condition is suspected to exist.	10-0
Unreadable	Radio signal is too weak to receive.	10-1
Out of Service	Unit, vehicle or person is not working	10-7
In Service	Unit, vehicle or person is working but not necessarily "available" or "on radio."	10-8
Available	Unit is in service ready to accept assignment, not necessarily by radio.	10-24
Not Available	Unit cannot accept another assignment, but may be "on radio."	10-7A
Prepare to Copy	Dispatcher is about to give lengthy message.	10-14
Go	You have been given clearance to transmit your message.	- -
Roger	Message received and understood.	10-4
Say Again	Repeat your message.	10-9
Stand By	Stop transmitting and wait for further instructions.	10-12
Disregard	Cancel your present assignment.	10-22
Off Radio	Unit is not capable of being contacted by radio, but may be "available."	10-7B
On Radio	Unit is capable of being contacted by radio, but not necessarily "available."	10-11
Responding	Unit is en route to assigned location.	10-17
Under Control	Situation is under control when no further assistance is anticipated.	- -
Telephone	Call by telephone specified number or person.	10-21
Priority	When transmitted, means that the following transmission must have immediate attention.	- -
In Pursuit	Unit is chasing a vehicle and requires assistance from other units.	- -
Traffic Stop	Unit is going to stop a motorist.	- -
Help Officer	Help me quick.	10-33
Affirmative	Yes.	10-4