How do Debit/Credit cards know how much money they should have? Especially before the Internet.

Question

When I slidey debit card, how does the card reader know if there is money on it?

I understand nowadays that the card reader probably just asks over the Internet how much money the account has, but debit cards are older than the Internet, so what did they do back then?

In: Technology

Answer 1

They used dialup networking that was available commercially since 50s. There were no ISPs but you could buy a modem, setup a computer that would answer incoming calls and transmit data. ATMs and point of sale systems dialed directly to a bank computer.