Duplex Printing Sold Separately
Keep in mind that many printers will only automatically print out on both sides of a page, if a separate duplexer is installed. This is the case with the widely used HP 600. The specs for a printer may state that it prints double-sided, but it may not do this automatically. The user may be required to re-feed the pages one by one.
The duplexer for the HP 600 will slide effortlessly in to the rear of the printer without the need to connect any cables, or tighten any screws. Beware of the fact that an ordinary power cord with a straight head can't be used with the duplexer. You'll need a cord with a right angle head like this one:
A standard power cord will prevent you from sliding the duplexer fully into position.