Samsung ML-2151N-XBH - Manual (Page 214)

P ROGRAMME I NSTALLING P RINTER O PTIONS F.7
F
Review the precautions on page F.2 and then follow this
procedure to install the network or serial interface card option in
your printer.
1 Unpack the network or serial printer card. Make sure that
there is no missing or damaged part.
2 Turn the printer power off and unplug all cables from the
printer.
3 Remove the two screws on the back of the printer, then
remove the control board cover.
4 Remove the two screws and the bracket from the control
board. You can discard the old bracket.