When was the Xerox Notetaker introduced?

The Xerox Notetaker computer was never introduced, in the sense of it being sold to the public. It was an internal Xerox PARC project started in 1978 and cancelled in early 1980 after only a few prototypes had been built.

Most of the pages about it on the web get some of the details wrong. All of the technical information can be found in Bitsavers or one of its mirrors. See Related Links, below. The series of memos there also documents the project's history.