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Practical writing on card and wallet payments, ISO 8583 and payment infrastructure in Afghanistan.
The same transaction behaves differently when the card is in the machine and when it is not. Here is how the two modes map to ATM, POS and mobile.
The message standard behind card networks has outlasted several generations of technology. That is a reason to rely on it.
One connection to the national switch replaces a separate connection to every other institution.
Every card transaction has an institution that accepts it and an institution that answers for the card. Many institutions are both.