In some cases, notification may be combined with the deliberate disabling of a product to prevent it from working, thus requiring the buyer to purchase a replacement. For example, inkjet printer manufacturers employ smart chips in their ink cartridges to prevent them from being used after a certain threshold (number of pages, time, etc.), even though the cartridge may still contain usable ink or could be refilled (with ink toners, up to 50 percent of the toner cartridge is often still full).[24] This constitutes "programmed obsolescence", in that there is no random component contributing to the decline in function.