Everywhere I've worked, the emergency code is 10-33. Never heard it used but heard plenty of emergencies where radio protocol goes out the window. Worst one was a jewelry store robbery just occurred that a detective from a neighboring department stumbled onto the offender in his getaway vehicle. You can hear him calling out the pursuit and asking for help with gunfire in the background as the offender is shooting at his squad. He kept begging for help even though he had a caravan of units behind him. After that day, the Sgt. started keeping his AR in his patrol car.