How do u disable duplex?

[copiertech2013]

working on a FS-4020DN.

Seems like an easy question,
How do you disable duplex?

The machine has had some issues jamming when using duplex, so company wants to turn off duplex completely.
We turned off duplex in the driver on the server. Still will duplex.
Turned off duplex on the machine itself. Still will allow the user to duplex.

Is there anything I'm missing or any suggestions on what I can do to disable duplex completely on this machine?

[blackcat4866]

Exactly how are you disabling duplex?

The machine will automatically block duplexing of transparency media type. Just designate the tray as tranparency media type, then default the driver to transparency media type. =^..^=

[HenryT2]

Check the page setup ( print properties ) of the file the user is sending to the printer;
if his software is telling the printer to duplex the print job, it will duplex .