Question 48G2

When calling another ship station directly, the appropriate menu choice refers to the mode of communication. **Simplex** mode uses a single frequency for both transmission and reception, but not simultaneously. One station transmits, and the other listens on the same frequency, which is the standard operational method for direct ship-to-ship communications on designated marine VHF channels. **Duplex** communication uses two separate frequencies for simultaneous transmission and reception, like a telephone call. While marine radios have duplex channels, they are primarily for public correspondence (connecting to the landline telephone network) or certain Coast Guard communications, not for direct ship-to-ship calling. Ch-28 and Ch-22 are specific channel numbers, not communication modes. Ch-28 is a duplex channel typically used for public correspondence, and Ch-22 is a duplex channel often used by the US Coast Guard for working traffic. Neither is the general "menu choice" for the mode of direct ship-to-ship contact.