An assembly for testing of smoke detectors, installed to detect the presence of smoke in ductwork or through a smoke protected opening, and includes a plenum rated hose assembly having a duct end and a smoke end. The sand control device is divided into compartments along its length that provide redundancy for particle filtration. The organization of the visitor is obtained. Two-dimensional electron gas generated at the interface between the undoped AlGaN layer and the undoped GaN layer and the first and second p-AlGaN layers form a pn junction in a gate region. A polarity controlling device sets residual toner to a second polarity opposite to the first polarity, before the residual toner left on the image carrier by the transferring device is conveyed to a corresponding position to the charging member.