Installing upgrades > 72I NSTALLING UPGRADESThis section explains how to install optional equipment into yourprinter. This includes:> duplex (two-sided printing) unit;> additional RAM memory;> hard disk drive.> additional paper tray> cabinetDUPLEX UNITThe duplex unit adds the function of two-sided printing, usingless paper and making large documents easier to handle. It alsoenables booklet printing, which uses even less paper and makeslarge documents even easier to handle.The duplex unit slides straight into the rear of the printer andrequires no tools to install.1. Unpack the new unit and remove any transit materialfrom it.2. Switch the printer off. It is not necessary to disconnectthe AC power cable.3. Ensure that the unit is the right way up, as shown, andpush it into the slot behind the rear panel. The panel willswing inwards as you push the unit into it. Push the unitall the way in until it stops and latches home.4. Switch the printer on and wait for it to warm up (about1 minute).