A terminal adapter, along with a value added network, is disclosed that interworks a plurality of terminals with a processing host to accomplish transaction processing. The terminals can use different protocols and typically incorporate card readers for completing financial or other types of transactions typically involving credit, debit, ATM or similar cards. The terminal adapter provides reliable and secure communication using a network based in part on the Internet as a primary form of communication. The terminal adapter also provides a secondary communication path in the event of a failure of the primary communication path, as well as automatic recognition of different terminal protocols, various security functions, error detection, and other network administration functions to ensure a flexible system and efficient transaction processing system.