ATM --> PBX --> USB Modem --> RPi --> Banking Application. The RPi turned ATM API called (done over POTS), into REST calls. One side would listen for the inco

ATM --> PBX --> USB Modem --> RPi --> Banking Application. The RPi turned ATM API called (done over POTS), into REST calls. One side would listen for the incoming call and decode the message, and the other side would call the custom banking application.