How does half-duplex transmission work?

• A. One way
• B. Two ways at any time
• C. Two way, but only one at a time (Walkie)
• D. Both directions simultaneously

Answer: (C)

Half-duplex transmission means two devices can communicate in both directions, but not at the same moment. The channel is shared, so only one side can transmit while the other listens, and they switch roles as needed. A common real-world example is a walkie-talkie: you press the talk button to speak, and only what you say is transmitted while the other person listens; when you stop, the other side can press to talk. This contrasts with simplex, which is one-way only, and full-duplex, where both sides can talk and listen at the same time. On a shared copper link, half-duplex often uses a control method to avoid collisions and enforce turn-taking, but the core idea is clear: two-way communication with one direction at a time.