The invention concerns a method of charging for the use of an internet service by a subscriber of a communications network, plus a service unit of this communications network and a service provider unit which furnishes the internet service. A method may be performed in a decision feedback equalizer. In one embodiment, the NVRAM module comprises copies of MRTs from each node operating within the cluster system. A TOF control module generates distance data based on the first time and the second time and determines whether at least a portion of a detected object is within a predetermined distance of the vehicle. The impurity removal flow paths function as filters to remove the impurities contained in the reaction gases.