A refrigerant cycle is provided with tandem compressors. Methods of constructing, installing, and servicing includes fluids filters of the type described. An actuating mechanism switches the main valve between the open position and the closed position. A set of exemplary embodiments apply a single or multiple set of alternating voltages to one or more terminals of a floating gate memory cell just prior to or during the signal integration time of a read process. The mobile device sends positioning information derived from the Navigation System signals to a server, the server comparing the positioning information to reference information received from base stations in order to determine its reliability.