A reference voltage generating circuit. This invention is specifically directed to providing valve plugs where the plug head material is different and distinct from the plug stem material and where each material is selected to optimize its performance. If the polycrystalline layers are deposited overlying the nanocrystalline layers, a high resistance can be written with narrow pulse width, negative voltage pulses. The registration information provided by the monitoring module maybe stored at the remote site in a database server having a database. Here, the two neighboring pixels correspond to a maximum pixel value and a minimum pixel value of the set of neighboring pixels. The control means causes the gripper device to grip an edge of the sheet at the first location, the drive means to move the gripper device from the first location to the second location, the gripper device to release the sheet at the second location, and the support device to move from the supporting position to the non-supporting position, dropping the sheet onto the stacking platform.