SDI is a three-letter abbreviation with many expansions. It's impossible to count exactly how many expansions it has, but it's surely one of candidates for the first place.
... device is covered by US patents 3,726,146 (1973) and 5,353,655 (1994) by L.A. Mishler and US patent 5,800,311 (1998) by P.S.Chuang.
External links
www.gyrotwister.de ...