At what age should you introduce baby Einstein like digital learning sources to kids?

You can start as early as baby is able to sit unsupported and focus on something. But it is best not to use digital sources for babies this young as it will let them be dependant on electronics. I've seen a lot of young children glued to iPads. Personally I do not allow my children to use iPad or phone. I teach them using physical source like flash cards and books etc. I feel that this will be better as it encourages them to read more often.