Mono Drum Chips
The imaging drum unit is the heart of the laser printer or photocopier. It transfers the print image to the paper. The light sensitive photoconductor drum is electrically charged by means of a laser beam, or an array of focused LEDs.
For printer models in this category the imaging drum unit is separate from the toner cartridge. This system is favoured by some manufacturers of monochrome printers including Brother, Oki, and Lexmark amongst others.
There is another type of cartridge known as the "all-in-one" type where the imaging drum is contained within the toner cartridge. The single cartridge system is favoured by Canon, HP, Pantum, Samsung and Xerox.
For models with a separate imaging drum unit the rated page life of the drum is usually significantly greater than of the toner cartridge. The toner cartridge can be replaced independently of the drum. This extends the life of the drum unit.
Most manufacturers use a smart chip on the drum unit to store the number of pages printed and other supplies information. The drum locks out when it reaches its rated page life. Typically the print quality is still very good at this stage. You may replace the chip to reset the page count back to zero, and use the drum unit for a second lifetime.
In this category are compatible (non OEM) chips for resetting monochrome drums. The chip will extend the life of the Photoconductor Unit provided it is working properly in other respects. For most models the chip simply fits in place of the original chip on the outside of the drum.