The Hewlett Packard 82143A is a small DC powered thermal printer than was designed to interface to the HP 41C calculator through one of its four expansion ports. I do not have any documentation for these printers so I dont know much about them. The little power connector on the back is for an AC adapter that provides the printer with 8VAC 3W max. I have two printers and one AC adapter. I will sell or trade the printer without the ac adapter if anyone wants it.