If you have specified a SELCAL (Selective Calling) code when connecting to VATSIM, controllers have the capability to send a SELCAL alert to your aircraft using that code. This feature is utilized during long flights over areas where the standard VHF radio does not provide sufficient range, and noisy HF frequencies are used instead. Pilots often decrease the volume to avoid listening to the HF static, and controllers can send a SELCAL alert to grab their attention when communication is required over HF.

When a SELCAL alert is received, you will hear a tone, and a message will appear in the main message area to notify you of the alert.