# 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 (CB) 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 (APCO), 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, (for example, name and description of missing person might be transmitted as follows: Name, age, height, weight, physical characteristics, clothing; if car used, the license, make, description and motor number. This information would actually be transmitted in the text of the message as follows: John Brown 28-5-9-165 medium build brown eyes dark hair dark suit light hat Mich. 35 lic. W 2605 Ford S 35 blue red wheels 2345678 may go to Indiana).
* 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 (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).

### In popular culture

Ten-codes, especially "10-4" (meaning "understood") 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" (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, as did the movie Smokey and the Bandit.
The New Zealand reality television show Ten 7 Aotearoa (formerly Police Ten 7) 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 (Out of service) and then a 10-42 code (ending tour of duty).

## Signals by era (North America)

| Signal | | | APCO Meaning | APCO Meaning | APCO Meaning | APCO Meaning | APCO Meaning | | |
| | 1937 APCO | 1939 First Published Set (17 signals) | 1940 (APCO Standards Committee) | 1955 (National Operating Procedure Committee) | APCO Project 2 (1967) | APCO Project 4 (1973) | APCO Project 14 (1974) | Clear Speech (c. 1971) (plain language to replace Ten Codes) | Phrase Word Brevity Code (c. 1979) |
| Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | Procedure and Officer Details | |
| 10-MAX | | AWOL | - | - | - | | Corrupt Officer | Officer not following orders | Insubord­ination/​Rogue Officer |
| | | | | | | | | | Go Ahead |
| | | | | | | | | | Under Control |
| | | | | | | | | | In Pursuit |
| | | | | | | | | | Traffic Stop |
| 10-0 | | | — | — | — | | — | Use caution | |
| 10-1 | | | Receiving poorly. | Receiving poorly. | Unable to copy - change location | | Signal Weak | Unable to copy - change location | Unreadable |
| 10-2 | | | Receiving well. | Receiving well. | Signals good | | Signal Good | — | |
| 10-3 | | | Stop transmitting. | Disregard last information | Stop transmitting | | Stop Transmitting | Stop Transmitting | |
| 10-4 | | | Acknowl­edgement. | Message received | Acknowl­edgement | | Affirmative (Ok) | Roger | Roger/​Affirmative |
| 10-5 | | | Relay. | Relay. | Relay. | | Relay (To) | Relay | |
| 10-6 | | | Busy. | Busy, stand by | Busy -Stand by unless urgent | | Busy | Busy | |
| 10-7 | | | Out of service. | Out of service. | Out of service (Give location and/or telephone number) | | Out of Service | Out at ... | Out of Service |
| 10-7 A | | | | | | | — | | Not Available |
| 10-7 B | | | | | | | — | | Off Radio |
| 10-8 | | | In service. | In service. | In service. | | In Service | Clear | In Service |
| 10-9 | | | Repeat, conditions bad. | Repeat | Repeat | | Say Again | Say Again | Say Again |
| 10-10 | | | Out of service—subject to call. | On minor detail, subject to call | Fight in progress | | Negative | — | |
| 10-11 | | | Dispatching too rapidly. | Stay in service | Dog Case | | ... On Duty | — | On Radio |
| 10-12 | | | Officials or visitors present. | Visitors or officials present | Stand by (stop) | | Stand By (Stop) | Stand by | Stand By |
| 10-13 | | | Advise weather and road conditions. | Weather and road conditions | Weather and road report | | Existing Conditions | Weather report/​road report | |
| 10-14 | | | Convoy or escort. | Convoy or escort | Report of prowler | | Message/​Information | — | Prepare to Copy |
| 10-15 | | | We have prisoner in custody. | We have prisoner in custody. | Civil disturbance | | Message Delivered | Disturbance | |
| 10-16 | | | Pick up prisoner at ... | Pick up prisoner at ... | Domestic trouble | | Reply to Message | — | |
| 10-17 | | | Pick up papers at ... | Pick up papers at ... | Meet complainant | | Enroute | — | Responding |
| 10-17 A | | | — | — | — | | — | Theft | |
| 10-17 B | | | — | — | — | | — | Vandalism | |
| 10-17 C | | | — | — | — | | — | Shoplifting | |
| 10-18 | | | Complete present assignment as quickly as possible. | Anything for us? | Complete assignment quickly | | Urgent | Urgent | Priority |
| 10-19 | | | Return to your station. | Nothing for you | Return to ... | | (In) Contact | Return to ... | |
| 10-20 | | | What is your location? | Location | Location | | Location | Location | |
| 10-21 | | | Call this station by telephone. | Call ... by phone | Call ... by phone | | Call (...) by Phone | Call ... | Telephone |
| 10-22 | | | Take no further action last information. | Report in person to ... | Disregard | | Disregard | Disregard | Disregard |
| 10-23 | | | Stand by until no interference. | Arrived at scene | Arrived at scene | | Arrived at Scene | On scene | |
| 10-24 | | | Trouble at station—unwelcome visitors—all units vicinity report at once. | Finished with last assignment | Assignment completed | | Assignment Completed | — | Available |
| 10-25 | | | Do you have contact with...? | Operator or officer on duty? | Report in person to (meet) ... | | Report to (Meet) ... | Meet ... or contact ... | |
| 10-26 | | | Can you obtain automobile registration information? | Holding subject, rush reply | Detaining subject, expedite | | Estimated Arrival Time | Detaining subject, expedite | |
| 10-27 | | | Any answer our number...? | Request driver's license information | Drivers license information | | License/​Permit Information | Drivers license information on ... | |
| 10-28 | | | Check full registration information. | Request full registration information | Vehicle registration information | | Ownership Information | Registration information on ... | |
| 10-29 | | | Check for wanted. | Check record for wanted | Check records for wanted. | | Records Check | Check for wanted on ... | |
| Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | Emergency or Unusual | |
| 10-30 | | | Does not conform to rules and regulations. | Does not conform to rules and regulations. | Illegal use of radio | | Danger/​Caution | — | Use Caution |
| 10-31 | | | Is lie detector available? | Emergency basis, all squads, 10-11 | Crime in progress | | Pick Up | — | |
| 10-31 A | | | — | — | — | | — | Burglary | |
| 10-31 B | | | — | — | — | | — | Robbery | |
| 10-31 C | | | — | — | — | | — | Homicide | |
| 10-31 D | | | — | — | — | | — | Kidnapping | |
| 10-31 E | | | — | — | — | | — | Shooting | |
| 10-32 | | | Is drunkometer available? | Chase, all squads stand by | Man with gun | | ... Units Needed (Specify) | — | |
| 10-33 | | | Emergency traffic at this station—clear? | Emergency traffic this station | EMERGENCY | | Help Me Quick | — | Help Officer |
| 10-34 | | | Clear for local dispatch? | Trouble at station, assistance needed | Riot | | Time | — | |
| 10-35 | | | Confidential information. | Major crime, blockade | Major crime alert | | —Reserved— | — | |
| 10-36 | | | Correct time? | — | Correct time | | —Reserved— | — | |
| 10-37 | | | Operator on duty? | No rush | Investigate suspicious vehicle | | —Reserved— | — | |
| 10-38 | | | Station report—satisfactory. | Hurry, but do not use red light or siren | Stopping suspicious vehicle (Give station complete description before stopping). | | —Reserved— | Traffic stop on ... | |
| 10-39 | | | Your Nr...delivered to addressee. | Use red light and siren | Urgent-Use light and siren | | —Reserved— | — | |
| General Use | General Use | General Use | General Use | General Use | General Use | General Use | Private Use | | |
| 10-40 | | | Advise if Officer...available for radio call. | Notification | Silent run - No light or siren | | | — | |
| 10-41 | | | Tune to ... kcs. for test with mobile unit or emergency service. | Car change at ... | Beginning tour of duty | | | — | |
| 10-42 | | | — | Crew change at ... | Ending tour of duty | | | Off duty | |
| 10-43 | | | — | Take school crossing | Information | | | — | |
| 10-44 | | | — | — | Request permission to leave patrol ... for ... | | | Request for ... | |
| 10-45 | | | — | — | Animal carcass in ... lane at ... | | | — | |
| 10-46 | | | — | — | Assist motorist | | | Assist motorist | |
| 10-47 | | | — | — | Emergency road repairs needed | | | — | |
| 10-48 | | | — | — | Traffic standard needs repairs | | | — | |
| 10-49 | | | — | Hourly report mark | Traffic light out | | | East bound green light out (etc.) | |
| Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | Accident and Vehicle Handling | |
| 10-50 | | | — | Auto accident, property damage only | Accident—F, PI, PD | | | Traffic (F, PD) Traffic Hit and run Injury No injury reported Unknown Private property, location | |
| 10-51 | | | — | Auto accident, wrecker sent | Wrecker needed | | | — | |
| 10-52 | | | — | Auto accident, personal injuries, ambulance sent | Ambulance needed | | | — | |
| 10-53 | | | — | Auto accident, fatal | Road blocked | | | — | |
| 10-54 | | | — | — | Livestock on highway | | | — | |
| 10-55 | | | — | Drunken driver | Intoxicated driver | | | — | |
| 10-56 | | | — | — | Intoxicated pedestrian | | | Drunk pedestrian | |
| 10-57 | | | — | — | Hit and run—F, PI, PD | | | — | |
| 10-58 | | | — | Is wrecker on the way? | Direct traffic | | | — | |
| 10-59 | | | — | Is ambulance on the way? | Convoy or escort | | | — | |
| Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | Net Message Handling | |
| 10-60 | | | What is next item (message) number? | What is your next message number? | Squad in vicinity | | | — | |
| 10-61 | | | Stand by for CW traffic on ... kcs. | CW traffic | Personnel in area. | | | — | |
| 10-62 | | | Unable to copy phone—use CW. | Any answer our Nr. ... | Reply to message | | | — | |
| 10-63 | | | Net directed. | Time | Prepare to make written copy | | | Prepare to copy | |
| 10-64 | | | Net free. | — | Message for local delivery | | | — | |
| 10-65 | | | Clear for item (message) assignment? | Clear for message assignment | Net message assignment | | | — | |
| 10-66 | | | Clear for cancellation? | Clear for cancellation | Message cancellation | | | — | |
| 10-67 | | | Stations...carry this item (message). | Clear for net message | Clear to read net message | | | — | |
| 10-68 | | | Repeat dispatch. | — | Dispatch information | | | — | |
| 10-69 | | | Have you dispatched...? | — | Message received | | | — | |
| Fire | Fire | Fire | Fire | Fire | Fire | Fire | Fire | Fire | |
| 10-70 | | | Net message (State net traffic). | Fire, phone alarm | Fire alarm | | | Fire | |
| 10-71 | | | Proceed with traffic in sequence (busy here). | Box alarm | Advise nature of fire (size, type, and contents of building) | | | — | |
| 10-72 | | | — | Second alarm | Report progress on fire | | | — | |
| 10-73 | | | — | Third alarm | Smoke report | | | — | |
| 10-74 | | | — | Fourth alarm | Negative | | | Negative | |
| 10-75 | | | — | Fifth alarm | In contact with | | | — | |
| 10-76 | | | — | Fire equipment needed | En Route | | | En route ... | |
| 10-77 | | | — | Fire, grass | ETA (Estimated Time of Arrival) | | | ETA (Estimated time of arrival) | |
| 10-78 | | | — | Set up command post | Need assistance | | | Request Assistance | |
| 10-79 | | | — | Report progress on fire | Notify coroner | | | Notify coroner (to be done by phone whenever possible) | |
| The 80 series is reserved for assignment by nets for local use. | The 80 series is reserved for assignment by nets for local use. | The 80 series is reserved for assignment by nets for local use. | The 80 series is reserved for assignment by nets for local use. | Personal Favors | — | | | | |
| 10-80 | | | ... tower lights at this station burned out. | — | — | | | Chase | |
| 10-81 | | | Officer Nr. ... will be at your station ... | — | — | | | — | |
| 10-82 | | | Reserve room with bath at hotel for officer Nr. ... | Reserve hotel room | Reserve lodging | | | — | |
| 10-83 | | | Have officer Nr. ... call this station by telephone. | — | — | | | — | |
| 10-84 | | | Advise telephone Nr. ... your city that officer Nr. ... will not return this date. | — | If meeting ... advise ETA | | | — | |
| 10-85 | | | Officer ... left this station for ... (Jefferson City) (Des Moines) at ... | — | Will be late | | | — | |
| 10-86 | | | Officer ... left this station for ... at ... | — | — | | | — | |
| 10-87 | | | Officer Nr. ... will be in ... if officer Nr. ... will be in. | — | Meet the officer at ______. | | | — | |
| 10-88 | | | What phone number shall we call to make station to station call to officer Nr. ...? | Advise phone number for station to station call | Advise present telephone number of ... | | | — | |
| 10-89 | | | Request radio service man be sent to this station... | Radio transmission | — | | | Bomb threat | |
| Technical | Technical | Technical | Technical | Technical | Technical | Technical | Technical | Technical | |
| 10-90 | | | Radio service man will be at your station .... | Transmit on alternate frequency | Bank alarm | | | Alarm (type of alarm) | |
| 10-91 | | | Prepare for inspection (date) ... (time) ... | — | Unnecessary use of radio | | | Pick up prisoner | |
| 10-92 | | | Your quality poor—transmitter apparently out of adjustment. | — | — | | | Parking complaint | |
| 10-93 | | | Frequencies to be checked this date. | Frequency check | Blockade | | | — | |
| 10-94 | | | Test—no modulation—for frequency check. | Give me a test | Drag racing | | | — | |
| 10-95 | | | Test intermittently with normal modulation for ... | — | — | | | Prisoner in custody | |
| 10-96 | | | Test continuously with tone modulation for ... | — | Mental subject | | | — | |
| 10-97 | | | — | — | — | | | Check traffic signal | |
| 10-98 | | | — | — | Prison or jail break | | | Prison/jail break | |
| 10-99 | | | — | — | Records indicate wanted or stolen | | | Wanted/​stolen | |

## 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 (call for help) | In use |

## 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 (FEMA) 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. As of 2011, 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 Brevity 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 (Received) | Message received and understood. | 10-4 |
| Say Again (Repeat) | Repeat your message. | 10-9 |
| Stand By | Stop transmitting and wait for further instructions. | 10-12 |
| Disregard (Recall) | 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 (Tel. # or person) | 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 (emergency). | 10-33 |
| Affirmative | Yes. | 10-4 |

### ICS Clear Text

In 1980, the National Incident Management System published a document, ICS Clear Text Guide, which was another attempt to create a replacement for Ten-codes. The list of code words was republished in the 1990 Montana Mutual Aid and Common Frequencies document.
ICS Clear Text Guide :
| Procedure word | Meaning |
| Unreadable | Used when signal received is not clear. In most cases, try to add the specific trouble. Example: "Unreadable, background noise." |
| Loud and Clear | Self-explanatory |
| Stop Transmitting | Self-explanatory |
| Copy, Copies | Used to acknowledge message received. Unit radio identifier must also be used. Example: "Engine 2675, copies." |
| Affirmative | Yes |
| Negative | No |
| Respond, Responding | Used during dispatch – proceed to or proceeding to an incident. Example: "Engine 5176, respond ..." or "St. Helena, Engine 1375 responding." |
| Enroute | Normally used by administrative or staff personnel to designate destinations. Enroute is NOT a substitute for responding. Example: "Redding, Chief 2400 enroute RO II." |
| In-quarters, with Station Name or Number | Used to indicate that a unit is in a station. Example: "Morgan Hill, Engine 4577 in-quarters, Sunol." |
| Uncovered | Indicates a unit is not in-service, because there are no personnel to operate it. |
| Out-Of-Service | Indicates a unit is mechanically out of service. Example: "Aburn, transport 2341, out-of-service." Note, when repairs have been completed the following phrase should be used: "Aburn transport 2341, back in-service, available." |
| In-Service | This means that the unit is operating, not in response to a dispatch. Example: "Fortuna, Engine 1283, in-service, fire prevention inspections." |
| Repeat | Self-explanatory |
| Weather | Self-explanatory |
| Return to | Normally used by communications center to direct units that are available to a station or other location. |
| What is your Location? | Self-explanatory |
| Call ____ by Phone | Self-explanatory |
| Disregard Last Message | Self-explanatory |
| Stand-By | Self-explanatory |
| Vehicle Registration Check | Self-explanatory |
| Is ____ Available for a Phone Call? | Self-explanatory |
| At Scene | Used when Units arrive at the scene of an incident. Example: "Perris, Engine 6183, at scene." |
| Available at Residence | Used by administrative or staff personnel to indicate they are available and on-call at their residence. |
| Can Handle | Used with the amount of equipment needed to handle the incident. Example: "Susanville Battalion 2212, can handle with units not at scene." |
| Burning Operations | Self-explanatory |
| Report on Conditions | Self-explanatory |
| Fire under Control | Self-explanatory |
| Emergency Traffic Only | Radio users will confine all radio transmissions to an emergency in progress or a new incident. Radio traffic which includes status information such as responding, reports on conditions, at scene and available will not be authorized during this period. |
| Emergency Traffic | Term used to gain control of radio frequency to report an emergency. All other radio users will refrain from using that frequency until cleared for use by the communications center. |
| Resume Normal Traffic | Self-explanatory |

## Related codes

Brevity codes other than the APCO 10-code are frequently used, and include several types:
* The California Highway Patrol uses ten-codes, along with an additional set of eleven- and higher codes.
* 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
* The New York Fire Department uses its own ten-code system.
* Fire and Emergency New Zealand uses a system of "K-codes" to pass fire appliance availability statuses as well as operational messages. For example, "K1" means "proceeding to incident", "K99" means "Structure fire, well involved", and "K41" means "fatality" (a reference to the Ballantyne's fire, New Zealand's deadliest, which killed 41 people). The New Zealand Police also use some K-codes, with completely unrelated meanings to those used by FENZ; 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. In radiotelegraph operation, a Q code is often shorter, and provides codes standardized by meaning in all languages – essential for international shortwave radio communications.
** Z codes are used for military radio communications NATO countries, and like Q codes are standardized across languages.