FS ALe 642 is a class of Italian Electric Multiple Unit trains built from 1991 to 1995 for use on secondary lines and for commuter traffic. In service since 1991. Description This class is strictly derived from the previous ALe 582 and ALe 724 EMUs, sharing most of the mechanical and technical characteristics. The main differences are in the electrical part (especially traction control and low tension circuitry) and for the presence of 2nd class only seatings. The frontal part containing cabins consists of a preformed structure made of polyester reinforced with fiberglass. They originally had the Navetta livery, painted in gray with orange and red lateral stripes; now they all have received the corporate green-white XMPR livery. Technical description Units arrangement Like the previous EMUs on which they are based on, Class 642 can be divided in one or more sections containing a varying number of elements: ALe 642.001 ÷ 60, the engine units with driving cabins (64 seats, 67 t); Le 764.101 ÷ 140, non motorized carriage units (76 seats, 45 t); Le 682.001 ÷ 022, non motorized carriage units with driving cabin (68 seats, 46 t). Each section must contain at least one ALe and one Le, with a driving cabin on each end; a train can be formed by a maximum of two sections coupled with Scharfenberg type automatic coupler. Basic section arrangement are: M + R + Rp M + R + R + Rp M + R + R + M M + Rp where "M" are ALe 642, "R" Le 764 and "Rp" Le 682. Electrical description Engine units employ four direct current traction motors placed inside the bogies, two for each one of them. They are fed by choppers, one per bogie; unlike ALe 724, where the regulation is shunt-chopper type and a resistor is used when accelerating at low speeds, a full-chopper system is used as on ALe 582 with the only difference that, in this case, Class 642s are fitted with three-frequency choppers (582s employ single frequency ones). Chopper regulation allows rheostatic braking (active above/until , about if also using pneumatic braking) and the current generated by motors can be sent to the overhead supply line if there are other trains able to absorb it. An interlocking valve limits to 0.4 bars the pressure into the brake cylinders of the ALes when electrically braking. Low tension circuitry employs 24 V