Abstract: In transferring powder images from a moving photoconductive support to a receiving material such as copy paper passing in contact with the support over a transfer roller, while both applying a direct current potential to effect image transfer and brushing the surface of the transfer roller to remove powder particles attracted to it from parts of the support. A potential effective for transferring the image is applied without hampering the cleaning action of the brush or brushes by maintaining between the support and the transfer roller a pulsating direct current which, for instance, has a frequency of 60 Herz or 50 Herz and preferably is generated by single phase rectification of a current formed by superimposing a sinusoidal alternating current and a direct current.