A method, an apparatus, and a computer program product are disclosed for detecting memory-related errors in a computer program during compiling of the computer program. In order to manage the occurrence of the condition of suds lock, the state of the washing machine related to the suds lock condition during spray pretreatment is determined by one or more of a number of methods. The NAC and its appliances may be operatively coupled to the system controller. A DC level fixing and offset canceling circuit fixes the DC level of each of the two output signals from the mixer and cancels the relative difference between the DC levels of the two output signals according to the level fixing control signal and the offset canceling control signals. The generated electric energy can also be converted to power line frequency.