Some HP printers are designed to work only with cartridges that have reused chips or electronic circuits from HP. These printers use dynamic security measures to block cartridges that contain a chip or electronic circuit not originating from HP. Regular firmware updates maintain the effectiveness of these measures and can block cartridges that previously functioned. Reused HP chips and electronic circuits from HP allow the use of reused, remanufactured, and refilled cartridges.