DEC 2100 Operator's Manual page 60

2. Lift the top cover open to the halfway position.
3. Rotate the print density adjustment dial so that the desired density
number is opposite the index triangle.
p
Numbers on the dial are displayed in increments of 2.
p
Number 1 is the darkest setting; number 9 is the lightest setting.
p
Although the printer is shipped with the dial set to number 5, you
can typically obtain acceptable print quality, prolong the cartridge
life, and reduce toner consumption by setting the dial to 7.
2–34 DEClaser 2100 Printer Operator's Guide
Fig 2-37, MLO-004848
Fig 2-38, MLO-004849