Concept:Intra-departmental communication refers to the exchange of messages within a single department or among members of the same organisation.
Explanation:Common media used for intra-departmental communication include the intercom, notice board, circular, bells, and buzzers.
These tools help share information quickly among staff in the same department or office.
A radiophone is a radio-based telephone used for long-distance or external communication, not normally for communication within a department.
Therefore, radiophone is the option that is not a medium for intra-departmental communication.
Answer:C. radiophone