Original: The Class 171 Turbostar is a type of diesel multiple unit ( DMU ) built by Bombardier Transportation ( previously ADtranz ) at their Litchurch Lane Works in Derby , England which is identical to the Class 170 , except for the replacement of the BSI ( Bergische Stahl Industrie ) coupler with a Dellner coupler .
Simplified: The Class 171 '' Turbostar '' is a type of DMU operated by Southern . The Class 171 is identical to the Class 170 , except for the replacement of the BSI coupler with a Dellner coupler .