The Eighth Edition of the Standard for Intrusion-Detection Units, UL 639, is being issued as an American National Standard. The following revisions have been made to the standard: (a) standard references have been updated, (b) the word "natural" has been deleted from the term "natural gray", (c) the text "No." when referring to wire sizes has been deleted and (d) the scope paragraph addressing investigation of new and different features of products has been deleted.