Duplex Printing
 

I'm trying to set up a printer in the printcap file so that it duplexes. I'm using append_z=duplex however the print jobs aren't duplexing. Does anyone know what code I should use for duplexing?

lab121_hp2500:\
:append_z=duplex:\
:sd=/var/spool/lpd/lab121_hp2500:\
:mx#0:\
:sh:\
:rm=libsrv:\
:rp=lab121_hp2500:\
:if=/usr/lib/filters/lpf: