Starting point is that radios are used as much as possible, because everyone can listen in. Through listening, you become aware of what's going down, and ideally you can get a jump on things. I had one call when we were returning the ambulance to the station when over the police channel I heard a call for the police, with the police dispatcher advising the police that he would be requesting medical. We were responding before our dispatcher toned us out.
Depending on the size of the local is how many primary channels you have. But basically the system is that the police have one channel, the fire department has a different channel, ambulances may have a third, and from ambulance to hospital in on a fourth. Backup channels exist for when the primary one is in use.
A lot of people involved in emergency services become radio junkies. In our ambulance we have the main truck radio, and a portable. When I was on the department, I also had a personal portable. So we would leave the truck radio on fire dispatch (fire/medical had a combined dispatcher). Second radio would be set to the police channel so we could monitor them. Third radio was set to hospital to ambulance so we knew what other rigs were bringing in, unrelated to our problem. With practice, you can listen on all these radios at the same time. At the hospital, they had several radios, each tuned to the different channels.
Let's run through how this would play out:
Fire dispatch: Call number (each ambulance has it's own number), please respond to GSW at address. Report is from a 9-1-1 call.
Ambulance: 321 responding.
Fire dispatch: 321, then more call numbers, 9-1-1 is reporting multiple victims (as the 9-1-1 reports multiply, they become more accurate. Initially you're only going to send one ambulance. As people report more victims, dispatch will decide more units are needed). Police are responding.
Ambulance: 321, thank you. Where do you want us to stage? (At this point, if I hadn't heard the police were responding, I'd ask my dispatcher to confirm. For GSW, you do not go into the scene until the police are done getting shoot at. At this point, the hospital would begin to listen closely.)
Ambulance: 321 staged. Waiting. (This tells our dispatch that we are parked near the scene, but out of any danger. Until the police tell us the scene is safe, we aren't moving.)
Fire dispatch: 321, PD advise scene is safe, proceed to scene. PD advise there are four victims, two critical. (Police will usually tell us the number of victims if they can. They might not know and just give an estimate.)
Ambulance: 321 on scene. Assuming command. (First ambulance on scene will establish overall command of all ambulance until a higher ranking officer arrives. The senior EMT/paramedic would go and look quickly at the victims. He would probably put tags on each patient, although not necessarily. He'd decide who gets treated first and who treats who. Once he gets done, he'll get back on the radio.)
Ambulance: 321 to Fire Dispatch. Please advice hospital that we have four GSWs. We have one status one, one status two, and two status threes. (Most departments use some sort of quick code. With our department, status one meant "Oh, shit," down to status four, which means you probably didn't really need to call the ambulance.) Please request transport instructions.
Fire dispatch would repeat the statuses, then call the hospital on the phone. Understand that the hospital had listened in on the original call. By the time fire dispatch called, someone with some authority would be on the phone. The hospital would decide how many patients they could handle and advise our dispatch which patient would be going where. Hospital at this point would have a good idea of what resources it would be needing.
Fire dispatch and the on scene commander would coordinate who was going where. As the ambulance was leaving, the scene commander would advise what hospital to proceed to.
As the ambulance was en route, it would call up the hospital:
Ambulance: 324 to hospital.
Hospital: Hospital, go ahead.
Ambulance: Have 20 year-old male, GSW, right upper quadrant and thigh, thigh has exit wound, vitals are ..., patient unresponsive to verbal stimuli, patient has two high flow IVs wide open, O2 15 liters per minute, airway inserted. ETA 6 minutes.
The hospital would then repeat the information. Then the hospital would advise what room we would be taking the patient to. The hospital might also ask for additional information.
By the time you get to the hospital, the doctor has already begun to plan what's going to happen.
Best of luck,
Jim Clark-Dawe