A method of converting a modulated optical signal to an encoded electrical signal is provided. A record is made of the identification information upon entrance of a vehicle into the parking area. 2 grams of residue per gram of crude feed. During a normal operating mode of the integrated circuit, the first power supply bus provides the first power supply voltage to the first plurality of circuit elements and the second power supply voltage is not provided to the second plurality of circuit elements. The filers use a single distributed lock to protect each version of the file system.