> The fact that ATMs need to provide money when disconnected
Is this a fact though? We provide ATM rentals/leases for our customers (though few ask for it these days) and I'm pretty sure they do not function if they are disconnected.
As far as I am aware a failure to connect to the issuing bank for a card will cause your card to be declined so that would lead me to believe their mainframes (and yes they are actually IBM mainframes in the cases I've experienced) must be online and connected.
Regarding the 24-48hr approval process.. that is more because of batches. And you're dealing with a responsible merchant (or host-capture environment) if you get those timeframes.
A merchant can wait for days to batch their credit cards in which case you're waiting as well.
