An electrostatographic printing machine comprising a main frame and at least one unit insertable into and removable from said main frame for cooperative association therewith in producing prints, said main frame and said removable unit having at least one electrical connection to conduct electric current therebetween comprising two electrical contacting elements, one on each of said main frame and said removable unit a first element comprising a plurality of resiliently flexible conductive fibers arranged in a brush-like configuration and the second element comprising a substantially continuous conductive contact surface for electrical contact with said brush each of said contacting elements being connected to an electrical component.