Final answer:
The control of an ABA card is read at the magnetic stripe, specifically the sentinel line, which contains the control information necessary for transaction processing, including the cardholder's account number and bank's routing number.
Step-by-step explanation:
The control of an ABA (American Bankers Association) card, often referred to as a banking card or bank card, is read at the magnetic stripe. Specifically, it's the bottom line of the magnetic stripe, also called the sentinel line, which usually contains the control information. This control information is vital for the proper processing of transactions and includes data such as the cardholder's account number and the bank's routing number.
The ABA card is widely used in banking transactions and the sentinel line helps to ensure that the transaction is carried out swiftly and accurately by providing essential information needed by the card reader to authenticate and process the transaction.