The flow of events during a cash withdrawal at an ATM.
sequenceDiagram
actor User
participant ATM
participant Bank
User->>ATM: Insert Card
ATM->>Bank: Verify Card
Bank-->>ATM: Card OK
User->>ATM: Enter PIN
ATM->>Bank: Verify PIN
Bank-->>ATM: PIN OK
User->>ATM: Request Cash
ATM->>Bank: Check Balance
Bank-->>ATM: Approved
ATM->>User: Dispense CashSequence