When the ratio of the amount of vaporized fuel to be introduced into an intake passage of an engine from a fuel tank through a purge passage pipe, a purge control valve, etc. The voltage device includes at least one MOS transistor in a well on at least one terminal of the oscillating circuit. A control circuit and method set the impedance value of the variable impedance termination devices by comparing voltage values at the output of the current mode output driver and current mode return driver. Such testing includes storing a query template when a received result of the query matches an expected result of the query.