Original: They consisted of four carriages - a second class driving trailer, a second class trailer, a second class motor car (with guard's/luggage compartment above which the Stone Faiveley AMBR pantograph was mounted) and a composite (1st and 2nd class) driving trailer.
Simplified: They consisted of four carriages - a second class driving trailer, a second class trailer, a second class motor car (with guard's/luggage compartment above which the pantograph was mounted) and a composite (1st and 2nd class) driving trailer.