Fujitsu fi-5950 Operator's Manual page 27

The adjustment is done by using the Operator Panel on the scanner.
Function
Hopper Height
Paper Thickness
Thin Thick
Send to Scan
When you press the  button, the hopper is raised one step higher.(Low  Middle  High)
When pressing the  button, the hopper is lowered one step lower.(High  Middle  Low)
Immediately after the scanner is turned on, the Hopper is initially set to Low.
HINT
16
2.5 Setting the Hopper Height