Riso HC5500 Series Reference Manual page 22

Let's Start Printing
The printing mode is switched ON/OFF with the PRINT/PAUSE key
of the Operation Panel.
Printing mode ON
Prints upon a command from the printer controller.
Printing mode OFF
The printer does not accept commands from the printer
controller and keeps waiting for a command from the
Operation Panel. Panel operations permit changing
settings, as well as adjusting position and contrast of the
data currently being printed.
US/UK-20
Lit green
Printing Mode ON
Not lit
Printing Mode OFF