Roland VersaUV LEJ-640 Service Notes page 294

INK EMPTY SENSOR
It detects whether the Ink Cartridge is empty or not.
INK CARTRIDGE IC SENSOR
It communicates with the IC chip of the InkCartridge.
INK CARTRIDGE SENSOR
It detects whether the Ink Cartridge is installed
or not.
DANCER ROLLER SENSOR
It measure the Dancer angle, carries out the weight
control, and then adjusts media tension.
5-5
CAPPING SENSOR
It detects the limit position of
the Capping Unit.