I don't have a ton of time today, but I thought that for crime writers and authors in the US this would be helpful. Also perhaps helpful for my readers outside the US, and certainly will help any readers of my blog understand what the heck I'm talking about:
In the United States, Emergency Medical Services (or EMS) refers primarily to pre-hospital medicine and patient transport. It's essentially the ambulance (and helicopter) folks. While there are many variations from state to state, this is basic break-down of the EMS world in Indiana. Each level builds on the previous.
First Responder - Provides first aid and CPR, arrives prior to ambulance
EMT-Basic - Provides basic life-support, including airway management and patient transport
EMT-Advanced - More advanced, including IV's and simple EKG's
EMT-Intermediate - More advanced, including endotracheal tubing
Paramedic - Provides advanced life-support.
In addition, many EMS units (especially volunteer units) employ drivers who are not medics and also medical assistants. Many fire departments require their members to be EMT's or at least first responders, because fire departments are typically in charge of extrication of patients from vehicles.
EMT, of course, stands for Emergency Medical Technician. Ambulance units like ours are typically BLS, meaning that we provide Basic Life Support. Our primary medic is an EMT. ALS, or advanced life support units, include a paramedic, and typically must run from a hospital.
I know on TV they always call the ambulance a, "bus." I'm sure people really do that, but around here call it a truck or an ambulance.
When you're paged, you're "toned out," because each unit has its own unique set of tones so that its members know when to respond. (Or, in this digital age, its pagers' know which which calls to react to.)
When we go out to respond to a call, we call it a run.
And, lastly, while we are encouraged to use plain English at all times on the radio, most old-timers still mix in a lot of ten codes and numeric signals. Many of these are local and peculiar to the service and system. (Which is one of the main reasons Homeland Security would prefer we use plain English.) Around here, Signal 1 means you're on scene, Signal 9 means you can disregard the call, and Signal 14 means a possible death. Code 1 means a transport at normal speed with no lights or sirens. Code 2 means to go quickly, but no lights and sirens. Code 3 means to go all out. A 10/11/12 is a possibly lethal cardiac event. A 10-50 is a car accident. Just to give you a sample...
Okay, hope there's some worthwhile information in here!