The PRSP DLL uses the purchase prerequisites mechanism to block the purchase flow when the license plate is entered. The DLL then gets a list of ticket types (audiences) for the user to select from. When the selection is made, rules and pricing info are fetched, and if successfully received, the DLL will respond to the CWT application to release the block and proceed with the purchase flow.
<PAYMENTSERVICE purchasePreRequisitesMode="Online">
