Continuity: In some episodes, crew members need to touch their communicator and state who or where they are and the person or place they wish to communicate with ("Riker to Picard", "Bridge to Engineering", etc.), while in other episodes, one only needs to state the information without touching their communicator, possibly using the ship's built-in communication system, but if that were the case, why use the communicators at all when they can just use the ship's built-in system. Additionally, the communicator always knows the correct person to contact even if there's more than one matching name (there's 1000+ people on the Enterprise, most of them crew members, it is unlikely that none of them share the same name).
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