Abstract: A developing system for a bore matrix in a printer using toner in the form of a dry toner powder, and comprising a feeder brush (3) which receives toner from a toner container (1), a printer brush (5) receiving toner from the toner feeder brush (3) and transporting same through bores of a bore matrix (8) and down to a document (9) to be printed, and means (15) for charging the toner particles by mechanically rubbing the toner particles (2) against the printer brush (5), and in which a means (19) may be provided for ripping free the charged toner particles (2), so that said particles form a cloud (7) of charged toner particles (2) adjacent the bore matrix (8), which pass down to the document (9) to be printed through open bores of the bore matrix (8).