This document discusses several models of communication:
1) The linear model depicts a one-way process from sender to receiver with no feedback. It is used in mass media.
2) The interactive model involves two-way communication between humans or machines through verbal or non-verbal exchanges.
3) The transactional model features an exchange of messages where the roles of sender and receiver alternate as they communicate.
4) The gatekeeper model represents how media outlets control the flow of information to audiences as gatekeepers.
5) The ecological model portrays a complex system of mediated communication between individuals, groups, messages, and language within different media environments.