Brother FAX-1820C - Manual (Page 172)

S - 8 SPECIFICATIONS
Consumable items
Ink Black and 3 individual color ink cartridges separate
from the print heads.
Service Life of Ink
Cartridge Approximately 500 page/Black cartridge at 5%
coverage
Approximately 400 page/Color cartridge at 5%
coverage with 600 x 150 dpi resolution (Fast).
These numbers are based on consecutive printing;
the numbers will vary based on print frequency and
number of pages.
The machine periodically cleans the print head to
maintain print quality. This process consumes a
small amount of ink.