Which communication type allows audio to be sent both directions, but only one at a time?

Half Duplex Communication is characterized by its ability to allow audio (or data) to be transmitted in both directions, but not simultaneously—only one direction at a time. This means that while one party is speaking or sending data, the other must wait until that transmission is complete before responding. This type of communication is often compared to a walkie-talkie system where one person speaks while the other listens, and the roles can be reversed only after the first person has stopped talking.

In contrast, simplex communication facilitates data transmission in only one direction, meaning there is no option for a response. Full duplex communication, on the other hand, allows simultaneous two-way transmission, which is more efficient for conversations requiring immediate feedback. Constant bitrate communication pertains to how data is transmitted at a consistent rate but does not define the directionality of audio transfer. Therefore, the definition and functionality of half duplex make it the correct choice for this question.