Epson Stylus CX6500 Basic Operation Gude page 56

The valve in the ink supply port is designed to contain any excess
ink that may be released. However, careful handling is
recommended. Do not touch the supply port of the ink cartridge
or its surrounding area.
This product uses ink cartridges equipped with an IC chip. The
IC chip accurately monitors the amount of ink used by each
cartridge, so even if a cartridge is removed and then later inserted
again, all of its ink can be used. However, some ink is consumed
each time the cartridge is inserted because this product
automatically checks its reliability.
When an ink cartridge becomes empty, you cannot continue
copying or printing even if the other cartridges still contain ink.
Before copying or printing, replace the empty cartridge.
In addition to being used in document copying or printing, ink
is also consumed in the following operations: print head
cleaning, self-cleaning cycle performed when this product is
turned on, and ink charging when an ink cartridge is installed in
this product.
Do not refill the ink cartridges. This product calculates the
amount of ink remaining using an IC chip built into an ink
cartridge. Even if the cartridge is refilled, the amount of ink
remaining is not recalculated by the IC chip and therefore the
amount of ink available for use does not change.
After an ink cartridge is replaced, if the ink is low it may become
empty. When a message appears to indicate the ink is low,
prepare a new ink cartridge.
54
Replacing Ink Cartridges