How does duplex transmission work?

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

Answer: (D)

Duplex transmission means you can send and receive data at the same time. In a phone system this is full duplex, allowing both parties to talk and listen simultaneously. This differs from simplex, which is one-way only, and from half duplex, where two directions can occur but not at the same time. On a phone line, outgoing and incoming signals are kept separate so both directions can be active at once, often with echo cancellation to keep the conversation clear. So the description that fits phones best is two ways at any time.