ATMs dispense cash & use either KenSwitch or PesaPoint as switches thus allows banks to expand their network of ATMs without actually installing ATMs.
As for using the card at merchants... I think it uses the VISA network/process.
Greedy when others are fearful,Very fearful when others are greedy - to paraphrase WB
Greedy when others are fearful. Very fearful when others are greedy - to paraphrase Warren Buffett