AID stands for "Application Identifier". An AID is an identifier created from two values used to identify the available applications on an EMV chip card or EMV hardware terminal. The application determines what network the transaction processes through.
An AID is made up of an RID (Registered Application Provider Identifier) and PIX (Proprietary Application Identifier Extension). The RID is the card brand (Visa, MasterCard, Discover, Amex, etc) and the PIX is the card issuer, (Bank of America, Wells Fargo, Chase, V Pay, Discover, Amex , etc.) This is who printed and configured the card and is usually the issuer (Example: The RID for Visa is "A000000003" and the PIX for V Pay is "2020". Making the AID value of "A0000000032020").
It is possible to have Multiple AID's loaded to a card, which can be displayed on the PIN pad for the cardholder to select during the transaction processing. When using EMV it is important to understand that the cardholder will not simply have a credit and debit selection. They will be selecting from applications that are common to the card and the EMV terminal. This will often include a credit application and a debit application but could include multiple credit or debit applications.
The file can be found in the ...\Shift4\EMV folder and will be listed with the device serial number first (DEVICESERIAL _EMVCONTACT.XML). The UTG builds the EMVCONTACT.XML from the settings in the EMVTERM file and pushes the EMVCONTACT.XML file to the Ingenico device.
The EMVCONTACT.XML file contains a listing of all of the Application Identifiers (AID) that should be enabled on the terminal and public keys. The AIDs determine which credit or debit network will be used to process an EMV transaction.
There may be circumstances where the EMV settings on the device are not updating properly during a Terminal Download.
In these scenarios, removing the EMVTERM and/or EMVCONTACT files from the EMV folder may allow the settings to push down successfully. Remove the EMVTERM file first and attempt the Terminal Download, if unsuccessful remove the EMVCONTACT file and attempt the Terminal Download again.