Using an HP 60 ink cartridge is a fairly straightforward process. To gain a better understanding of how they work, it may be helpful to learn a bit about how inkjet printers work in general. A typical inkjet printer consists of a variety of electrical components. The first and foremost important component is the print head assembly. The print head assembly contains a print head which uses a series of nozzles to spray droplets of ink onto the printer paper. The print head gets its ink from ink cartridges connected to it, which are basically reservoirs of ink that contain various colors of ink. Some manufacturers combine the various color reservoirs into one cartridge, while others build separate cartridges so that individual colors may be replaced one at a time. Some cartridges even include the print head itself. These components, whether separate or built together into one unit, are controlled by a print head stepper motor. The stepper motor is what moves the print head assembly back and as the print head delivers ink to the printer paper. Some inkjet printers include a secondary motor used to “park” the print head into a safe position when not in use to protect it from damage when not in use. The print head assembly and primary stepper motor are connected by a belt similar to fan belts used in automotive engines (but on a much smaller scale). Along this belt is a stabilizer bar used to produce controlled, precision movements. The printer head assembly would be useless if there wasn’t some way to get the paper into and out of the printer. This is where the paper feed assembly comes in. The paper feed assembly is made up of a tray/feeder, rollers, and a stepper motor. Printers use either a tray or a feeder to hold multiple sheets of paper. A set of rollers pull the paper into the printer from the tray/feeder much like rollers on a typewriter do. The rollers continue to pull the paper into the paper bit-by-bit to allow the print head assembly to make multiple passes. A stepper motor is connected to the rollers to provide power for their movements. This motor advances the paper just enough for the print head to print the next line on the paper. Motor movements and ink dispersal are all governed by control circuity, which serves like a “motherboard” found in a typical personal computer. This control circuity contains memory and a microprocessor that handles all of the printer’s operations. It is also responsible for decoding information sent to the printer from a computer, as well as reporting progress and status information back to the computer. Data transmissions are passed back and forth between the printer’s control circuitry and its connected computer through an interface port. Traditionally printers interfaced with computers using parallel or serial interfaces. These interfaces are rapidly being replaced with the newer USB interface standard. Of course, no motor or circuitry can operate without electricity, which is why every printer requires the use of a power supply. Some models make use of external transformers, with others incorporating a power supply within the units themselves.