DuckCorp Dico

Found one definition

1.                 From The Jargon File (version 4.4.7, 29 Dec 2003):
                   
   
   
                   
                     
   DED
    /D·E·D/, n.
       Dark-Emitting Diode (that is, a burned-out LED). Compare SED, LER, 
    write-only memory. In the early 1970s both Signetics and Texas instruments
       released DED spec sheets as AFJs (suggested uses included “as a power-off
       indicator”).