with two cabs. The performance was finally established at for a continuous power rating of 2,580 kW and a mass of ; the increase in power allowed a slightly higher speed in freight ratio but the excessive flexibility of the suspension limited the maximum speed in passenger ratio; the redesign of the general architecture was accompanied by a significant increase in weight, which seems to have been clearly underestimated in the preliminary study, and a slight increase in length. Description Technical characteristics The BB 16500 were single-phase 25 kV/50 Hz, medium-power machines, built in the Alsthom factories in Belfort . Each locomotive consisted of a chassis which supported the two driver's cabs and three removable covers, each of which includes part of the sides and the roof, and the end covers supporting the pantographs. The shape of the body, long , was inspired by those of the first CC 7100s . It included, when the locomotives were first put into service, cab glazing allowing a wide panoramic view thanks to the provision of corner windows. These were replaced by sheet metal uprights during major overhauls of the locomotives between 1965 and 1970. The power train incorporates a large part of the elements already used on the BB 12000 and BB 16000 classes. The rectifiers, two mercury vapor igniters, supply the traction motors with rectified and smoothed current. As deliveries and technical improvements progressed, the ignitrons were replaced by later types of rectifiers, then finally by silicon diodes; this last type, more powerful, is finally applied to the whole of the seriesduring overhauls. As provided for in the specifications, the short-wheelbase, , single-engine bogies had a gear ratio change that could be operated when stationary, a device that sometimes tended to jam; three sets of reduction gears, with slightly different ratios, were fitted to the locomotives. The first batch, BB 16501 to BB 16654, had a suspension by elastic return legs and pivots; while the remaining locomotives, BB 16655 to BB 16794, had a pendular suspension. To improve cab comfort, the fitting of a double-decker suspension, replacing the original systems in place, was carried out on 120 locomotives from 1998 to 2003. 294 members of the class were built in six years. They were ordered in several successive stages, as electrification progressed in the north and east. In 2021, they constitute the largest series of electric locomotives ordered by the SNCF.