🔍 Key Concepts

• MF/HF transceiver operating modes used for different types of communications (voice vs data) • What TLX commonly indicates on GMDSS-capable radios (hint: think about text/telex-type transmissions) • Differences between DSC, SSB voice, and NBDP/SITOR functions on MF/HF sets

💭 Think About

• Ask yourself: When would a shipboard operator choose a mode that relates to "telex" or text-based messages instead of voice? • Which of the listed modes is specifically associated with narrow-band direct printing / text communications rather than standard radiotelephone voice? • Does TLX usually appear when selecting a distress/urgency alert format, or when selecting a working channel/mode for printing text messages?

✅ Before You Answer

• Confirm which option is tied to narrow-band direct-printing (NBDP) services historically used as radiotelex at sea • Verify which modes from the list are primarily voice modes, and which are data/text modes • Check your GMDSS MF/HF radio manual or study guide for how the display changes when switching between voice, DSC, and telex/NBDP modes