Compounds of formula I:wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 and n are as defined in the description, processes for the preparing the compounds, new intermediates employed in the preparation, pharmaceutical compositions containing the compounds, and uses of the compounds in therapy. An image owner performs a user registration with respect to an image managing server 2 by employing an image owner terminal. The converter also comprise a third circuit which is adapted to receive the first and second DC voltages from first and second circuits to generate a selectable output DC voltage. The method can be placed on computer readable media.