As an author, you’re not expected to know everything, just what you’re writing. Not all writers know the 10-codes that LEOs use, nor are the codes something you really need to memorize if you only need a squad to acknowledge a call or report that they’re 10-7 for lunch.
Here is a reference list of 10-codes used by law enforcement officers across the U.S:
| 10-0 | Caution |
| 10-1 | Unable to copy |
| 10-2 | Good signal |
| 10-3 | Stop transmitting |
| 10-4 | Acknowledgment (Okay) |
| 10-5 | Relay |
| 10-6 | Busy (unless urgent) |
| 10-7 | Out of service / unavailable |
| 10-8 | In service / available |
| 10-9 | Repeat |
| 10-10 | Fight in progress |
| 10-11 | Dog chase |
| 10-12 | Stand by |
| 10-13 | Weather/road report |
| 10-14 | Prowler |
| 10-15 | Civil disturbance |
| 10-16 | Domestic disturbance |
| 10-17 | Meet complaintant |
| 10-18 | Quickly |
| 10-19 | Return to location |
| 10-20 | Location |
| 10-21 | Call by telephone |
| 10-22 | Disregard |
| 10-23 | Arrived at location |
| 10-24 | Assignment complete |
| 10-25 | Report/meet in person |
| 10-26 | Subject detained – expedite |
| 10-27 | Driver license information |
| 10-28 | Vehicle registration information |
| 10-29 | Check for wants/warrants |
| 10-30 | Unnecessary use of radio |
| 10-31 | Crime in progress |
| 10-32 | Subject with gun |
| 10-33 | Emergency |
| 10-34 | Riot |
| 10-35 | Major crime alert |
| 10-36 | Current time |
| 10-37 | Investigate suspicious vehicle |
| 10-38 | Stopping suspicious vehicle |
| 10-39 | Emergency/urgent (lights/siren) |
| 10-40 | Run silent (no lights/siren) |
| 10-41 | Beginning tour of duty |
| 10-42 | Ending tour of duty |
| 10-43 | Information |
| 10-44 | Permission to leave scene |
| 10-45 | Dead animal carcass |
| 10-46 | Assist motorist |
| 10-47 | Emergency road repair at location |
| 10-48 | Traffic sign repair at location |
| 10-49 | Traffic light out at location |
| 10-50 | Accident (fatal, injury, property damage) |
| 10-51 | Tow truck needed |
| 10-52 | Ambulance needed |
| 10-53 | Road blocked at location |
| 10-54 | Livestock on roadway |
| 10-55 | Intoxicated driver |
| 10-56 | Intoxicated pedestrian |
| 10-57 | Hit and run (fatal, injury, property damage) |
| 10-58 | Direct traffic |
| 10-59 | Convoy or escort |
| 10-60 | Patrol car in vicinity |
| 10-61 | Personnel in area |
| 10-62 | Reply to message |
| 10-63 | Prepare to make written report/copy |
| 10-64 | Message (local delivery) |
| 10-65 | Message assignment |
| 10-66 | Cancel message |
| 10-67 | Clear for message |
| 10-68 | Dispatch information |
| 10-69 | Message received |
| 10-70 | Fire alarm |
| 10-71 | Advise type/nature of fire |
| 10-72 | Report on fire in progress |
| 10-73 | Smoke report |
| 10-74 | Negative |
| 10-75 | Make backup |
| 10-76 | En route |
| 10-77 | ETA (Estimated Time of Arrival) |
| 10-78 | Need assistance |
| 10-79 | Notify Coroner |
| 10-80 | Chase in progress |
| 10-81 | Brethalyzer report |
| 10-82 | Reserve lodging |
| 10-83 | Work school crossing |
| 10-84 | Advise ETA |
| 10-85 | Delayed due to |