EAS Insertion Feature: Inserts digital video from an Emergency Alert System (EAS) into all of the programs of your ATSC digital transport stream. The D2Alert system constantly monitors the EAS digital video signal and when a valid alert is found, it is automatically inserted into all of the configured programs until the alert is complete.. NOTE. For the FLEX 3000, THE 3500 UPGRADE FEATURE MUST BE INSTALLED PRIOR TO ALERT FEATURE