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70 Smartcard Interoperability Issues for the Transit Industry Reader Agency Clearinghouse Clearinghouse Card B B B A Figure 12. Figure data flow logic. Depending on agency size and the supplier's system design, the functionality of the station/local tier and the agency tier can be consolidated into a single server or workstation (com- puter). A typical smartcard fare payment system is an off-line system; data are stored at each tier and periodically forwarded to the next tier or to the central system. In contrast, credit and debit card transactions are conducted on line; the transaction is authorized before approval. 5.2 Identification of the Data Types The following two types of data flow among the five tiers: Configuration Data-Includes all data a device needs to conduct a secure and appropriate fare payment transaction and Usage Data-Primarily consists of the transaction records associated with each device, but includes any recorded alarms or events. All data transferred between each tier in the system architecture may be categorized as con- figuration or usage data. Configuration data are generally transferred to the device tier at the start of operation. For buses, start of operation may occur when a driver logs on before pulling out of the depot. On a gated rail system, start of operation may begin before trains begin the morning rush hour. Usage data are transferred at the end of an operating cycle and at a predetermined cut-off time. Usage data need to be transferred to the central system in sufficient time to allow processing and settlement to be completed according to agency requirements. Central System Tier Agency Tier Station/ Local Tier Device Tier Card Tier Figure 13. Conceptual smart card system architecture.