Why Automatic Link Establishment (ALE) radios continuously scan a preset list of channels, listening for short digital bursts that carry station addresses (call signs). When a radio hears its own address on one of the scanned channels, it stops scanning, handshakes with the caller, and the link is established on whichever channel is currently propagating best. Stations also transmit periodic "soundings" so others can build a table of which channels reach them.
Watch out The internet-monitoring choice describes internet-linked systems like Winlink gateways or DMR networks, not ALE, which is designed to work entirely over HF radio with no outside infrastructure.
ALE = Automatic Link Establishment: scan the channel list, wake up when you hear your own call sign.