The APS is the system that provides and controls the pressurization of the ink in the Ink Cartridges and is located under the ISS. The key purpose of this system is to ensure the minimum required ink pressure at the inlet to each Printhead respectively at the required print rates. The APS is also used to provide pressure for tube purge and as part of the blow prime system operation.

The APS pressurizes the ink in the Ink Cartridge bags by pressurizing the air around them. The Printer controls the air pressure using the pump with feedback from the sensor; when required the valve is opened to depressurize the air circuit. This allows control of the ink pressure at the inlet to the Printheads.