This HP Laserjet 4100 is available in four configurations.

HP LaserJet 4100
The HP 4100 comes standard with 16 MB RAM and one 500-sheet tray.
HP LaserJet 4100 N
The HP 4100N comes standard with 32 MB RAM, an HP JetDirect card for connecting to a network, and one 500-sheet tray.
HP LaserJet 4100 TN
The HP LaserJet 4100TN comes standard with 32 MB RAM, an HP Jet Direct card for connecting to a network, and two 500-sheet trays.
HP LaserJet 4100 DTN
The HP LaserJet 4100DTN comes standard with 32 MB RAM, an HP JetDirect card for connecting to a network, two 500-sheet trays, and a LaserJet 4100 duplexer.

Product Data Sheet -- HP LaserJet 4100 (313 Kb pdf file)
Users Manuals available at HP's website.