G PHYSICS
G03 PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
G03G ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
G03G21/00 Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
G03G21/16 Mechanical means for facilitating the maintenance of the apparatus, e.g. modular arrangements