Abstract: A color ink jet printing device has an off-board ink reservoir for each color being printed. Each reservoir comprises at least two separately replaceable cartridges from which ink is supplied under positive pressure to refill replaceable printhead cartridges. A visual indicator is provided for each off-board cartridge to indicate when the cartridge is empty and this indicator is turned on if the ink supply in the cartridge is exhausted during a refill operation. Printing is not stopped until all off-board cartridges holding one color of ink are empty. At this time the empty cartridges that held any color ink, are replaced. After each operator intervention to replace empty cartridges, the volume of each color ink will be (N−1)/N of maximum reservoir capacity where N is an integer greater than one and represents the number of cartridges in the reservoir.

Abstract: There is disclosed a closely arranged file of flexible rotating disk memory elements in which a disk may be randomly accessed with minimum error and relatively rapid access time. This disk system utilizes different diameter disks which are arranged in an ascending order in a sub-stack, are rotated at a relatively slow speed. A plurality of the sub-stacks, wherein there is a correspondence between the same diameter disk of each stack, are utilized to provide for a large memory capacity. Microprocessing techniques are utilized for sub-stack and disk selection.