A method to reduce lost postal revenue by identifying and sorting a mail piece by determining whether algorithmically-resolved image data corresponding to the mail piece indicates that the mail piece is business reply mail. The film feeding device also has a mechanism which is arranged to disconnect and reconnect the contact, wherein the mechanism is controlled either on the basis of the film tension or on the basis of the location of the film feeding device on the track, or on the basis of them both. A command is issued for turning off the components of the half bridge wherein the failure occurs, and the operation of the DC-DC conversion circuit 3 corresponding to the voltage polarity to be output by the half bridge is stopped. Each edge node has a channel to a switch unit in each column and a channel from each switch unit in a selected column. The first and second subelements provide first and second flow paths in parallel with each other along designated flow path portions.