Abstract: In a printer with an electrically chargeable image drum, such as a laser or a LED printer, for imprinting a medium by transferring toner to the medium, including, arranged around the image drum, a charging unit, a writing unit and a toner unit, the toner unit is disposed at a predetermined angular distance from the charging unit and a sensor is disposed at essentially the same angular distance from the charging unit to determine the charge of the image unit at the toner location for adjusting the voltage of at least one of the charging unit and the toner unit depending on the charge voltage of the image drum as determined by the sensor.

Abstract: In an apparatus for accurately imprinting print images onto sections of a edetermined length of a continuous unmarked foil, wherein a printer is disposed at a distance from a foil section delivery device which receives from the printer unprinted foil along a predetermined path, a foil sensor is arranged along the foil path which sensor has an output connected to the printer for supplying to the printer a printing signal when the length of the foil between the delivery device and a point on the foil corresponding to the beginning of a section to be imprinted is a predetermined multiple of the length of the foil sections to be imprinted so as to initiate printing of the printer accurately within a section of the foil.