What does blinkenlights mean?

blinkenlights meaning in Urban Dictionary

a humorous hacker's term for diagnostic lights on old mainframe computers and contemporary community hardware. The word is meant to provide the average English speaker the effect it is a German term. The word arises from a warning sign written in mangled mock German and usually imprinted in a blackletter-Gothic font, which used is preferred under computer room private inside U.S.A.