Which describes duplex operation?

• A. Uses one frequency to transmit and receive
• B. Uses two frequencies and allows one way communication
• C. Uses two frequencies and allows simultaneous two way communication
• D. VoIP with push to talk for radios and non radio devices over IP

Answer: (C)

Duplex operation means you have two separate paths for transmitting and receiving, using two different frequencies so you can talk and listen at the same time. This separation prevents the transmitted signal from interfering with what you’re receiving, enabling real-time two-way conversation. In radio systems, a common example is a repeater that receives on one frequency and transmits on another, allowing users to communicate back and forth without having to stop to switch modes. If only one frequency were used for both directions, you’d have to take turns speaking or would struggle with signal collisions—that’s simplex or half-duplex, not true duplex. The VoIP option describes how voice is carried over IP networks, not the radio’s duplex capability, so it doesn’t define simultaneous two-way radio communication.