Definitions
"10-4" means...
Acknowledged
You're confirming receipt of a message from dispatch.
10-4
10-4 at 10-20, copy?
Acknowledged at location, do you copy?
"10-20" means...
Location
During a radio call, dispatch asks for your location.
10-20
10-9, 10-23 at Park Central
Please repeat, on scene at Park Central
"10-9" means...
Repeat your message
The Officer has arrived on scene.
10-23
10-33 in progress near the 10-20
Emergency in progress near location
"10-8" means...
Available for Service
You've received an unclear message, you ask your partner to repeat.
10-9
10-8 at 10-20
Available at Location
"10-33" means...
Emergency; situation is critical
In a school scenario, you report an emergency that demands immediate attention.
10-33
10-4, then proceed to 10-20 for a 10-33.
Acknowledged, go to the location and handle emergency.