🔍 Key Concepts

• SELCAL (Selective Calling) in aviation radio communications • How long-range HF/VHF voice communications are normally monitored by flight crews • Difference between calling/alerting systems vs. encryption, navigation, or calibration systems

💭 Think About

• Think about what problem SELCAL is designed to solve for long flights over oceans or remote areas where HF radios are used. • Which option describes something that would reduce the need for the pilots to listen continuously to a noisy frequency, yet still lets the ground station reach them when needed? • Look at each choice and ask: does this describe a calling/alerting function, or something else like encryption, navigation, or tuning?

✅ Before You Answer

• Identify which option clearly describes a ground station initiating a call to a specific aircraft or group. • Eliminate any options that deal with encryption, distance calculation/navigation, or receiver calibration, since SELCAL is not primarily for those purposes. • Confirm that the correct choice explains that pilots do not have to continuously monitor the frequency to know when they are being called.