What power output do most portable radios have EMS?

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Communication in EMS is essential. Patients must be able to access the system, the system must be able to dispatch units, EMTs must have a means of communicating with medical direction and receiving facility, and EMTs must be able to communicate vital information to other personnel. It is a complex network composed of people, equipment, and facilities. 

Equipment

A base station is a radio operated from a fixed site such as a dispatch center, hospital, or some other location. It usually runs off community electrical power and transmits at much higher power than smaller, portable radios. Alternative power in the form of generators or a set of batteries are usually available.

Mobile radios are radios that are mounted in vehicles such as ambulances or fire-engines. They are much more powerful than portable radios. Range is less than 20 miles at a broadcast strength of less than 50 watts.

Portable radios, or "walkie-talkies" are designed to be carried or worn by individuals and operate off a small internal battery pack. Transmit power is usually under 5 watts and range is limited. They allow communication from the patient's side.

A repeater is a radio unit that receives a signal from another radio unit and rebroadcasts it, boosting the signal strength in the process. Some rebroadcast by converting signals to radio and others do so by converting to microwaves. It may also convert the signal to a telephone signal and send the communications through public or dedicated telephone lines.

EMS radio communication takes place in the VHF low band, VHF high band, and UHF band. VHF low band is the radio frequencies from 32-50 megahertz (MHz). They are able to follow the shape of the earth allowing communication over long distances. These frequencies are more susceptible to interference from, weather, buildings, and electrical equipment. VHF high band is the radio frequencies between 150 and 174 MHz. These radio waves travel in a straight line and do not bend to follow the curve of the earth or around obstacles. The straight line of site needs to be clear and free from obstructions. They are less susceptible to interference. UHF bandincludes the frequencies in the 450 to 470 MHz range. They are almost interference free and offer some of the cleanest communication frequencies available. These are most often used for telemetry, which is the transmission of electronic signals over the radio such as the ECG.

Digital radio equipment is computer controlled, highly reliable, and error free. The 800 MHzfrequency equipment is very costly, has the shortest range, and requires numerous repeaters. 

The chief advantage of cellular phones is low cost and high efficiency. The disadvantages include no protected channels or frequencies for EMS and competition with the general public for use.  

Sophisticated global positioning systems are becoming more common in EMS systems.

Dispatchers are highly trained and experienced to function in the modern dispatch center. In many states, there are established training and performance standards for dispatch personnel.

The most common method for accessing the EMS system is the telephone. In the late 70's and early 80's, callers became able to call 9-1-1 instead of worrying which number to call. All 911 calls arrive in a single location, known as a public safety answering point (PSAP). The PSAP may channel the calls to the appropriate emergency response agency or may perform actual dispatch functions. Enhanced 911 involves technology that allow the dispatcher to see immediately the street or billing address of the incoming call, based on telephone company records. This can pose a problem for cell phone users who have their calls routed to the nearest cell tower rather than the dispatch center for the responsible jurisdiction. 

System status management is a method of deploying EMS resources in a dynamic pattern that is based on anticipated call volume and location. EMS vehicles are kept constantly moving in an attempt to provide maximum coverage with the least amount of resources expended. 

EMS dispatch may give EMTs additional information about the incident while en route. EMS personnel should also advise the dispatch center when the unit arrives on the scene. The "on scene" notification implies when at the patient's side.

   EMTs should follow the basic radio guidelines below:

• Make sure the radio is on and properly adjusted.
• Listen to the frequency to make sure that there is no traffic before transmitting.
• Think through the message before pushing the transmit button.
• Press the talk switch on the microphone and wait 1 second before speaking.
• Speak clearly and distinctly.
• Use plain English.
• Keep transmissions brief and avoid use of unnecessary phrases like "thank you," or "please."
• Protect the patient's privacy. Every word said can be heard by anyone with a scanner. Do not transmit the name of the patient.

   When reporting over the radio, the following information should be given in the order listed:

1. Identify unit and level of provider.
2. Estimated time of arrival (ETA).
3. Age and sex of the patient.
4. Chief complaint.
5. Brief, pertinent history of the present illness.
6. Major past illnesses. Mental status.
7. Baseline vital signs.
8. Pertinent findings of the physical examination.
9. Emergency medical care given.
10. Response to emergency medical care.