What is SELCAL used for in aviation?

• A. Encrypted cockpit voice transmissions
• B. Establishing communication between pilots and flight dispatchers
• C. Routing air traffic between sectors
• D. Identifying aircraft by call sign

Answer: (B)

SELCAL is a selective calling system that lets ground stations alert a specific aircraft on a shared radio frequency that a voice message is for them. Each aircraft has a unique SELCAL code; when a station wants to reach that aircraft, they transmit the code and the cockpit’s SELCAL receiver decodes it, triggering an audible and/or visual alert. The crew then switches to the voice channel to hear the message. This reduces the need for crews to continually monitor the radio, which is especially useful on long oceanic or remote routes. It isn’t encryption, it doesn’t route air traffic, and it isn’t about identifying the aircraft by call sign—its purpose is to establish communication by notifying the correct aircraft to listen for a ground transmission.