A financial transaction processing system enables processing transactions from various types of card activated terminal devices which communicate using a variety of electronic message formats. A modified single chamber airbag can be used as the primary chamber of the two-chamber airbag. The instructions allows the controller to monitor a fluid level in a well with the combined arrangement to compile a history of respective measurements for both sensors, and, in the event of an unexpected discrepancy between the measurements, to automatically calibrate the sensor arrangement according to the history of respective measurements to re-establish a correlation between the sensors. A groove is formed between the cap and teeth formed at its circular outer periphery.