TA Triumph-Adler LP 4024 - Manual (Page 221)

Installing Option Units
D-6
D.2.2 DU-60 Duplexer
Install the option duplexer immediately below the printer. By combining
the two binding modes (short edge bind and long edge bind) with the two
printing orientations (portrait and landscape), duplex printing is possible
in four different methods (see Setting Duplex Printing on page 1-101 ).
Duplex printing can be specified from the application (printer driver).
1
Remove the nine tapes and the pad from the duplexer.
2
While pushing the rear cover release lever inward, remove the
duplexer rear cover.
3
Turn off the printer and disconnect the power cord and printer cable.