Original: The British Rail Class 312 is a type of alternating current (AC) electric multiple unit (EMU) built in 1975-1977Marsden (1982), page42 intended for use on outer-suburban passenger services.
Simplified: The British Rail Class 312 is a type of alternating current (AC) electric multiple unit (EMU) built in 1966-1974Marsden (1982), page42 intended for use on outer-suburban passenger services.