Final answer:
When communicating within the EMS system, it is important to listen before transmitting and speak clearly. Stating your ID number and unit number is not necessary unless required.
Step-by-step explanation:
When communicating within the EMS system, you should remember to listen before transmitting. This allows you to gather all the necessary information and ensures effective communication. Speaking with your lips directly on the microphone is not necessary, as long as you speak clearly and enunciate your words. It is important to begin talking only after depressing the microphone button to avoid accidental transmissions. Also, it is not necessary to state your ID number and the number of the unit you are calling unless specifically required by the EMS protocol.