first section between Federico Lacroze and Callao opened on 17 October 1930 and was 7.021 km in length. The Argentine President, José Félix Uriburu, travelled on the maiden journey. On 22 June 1931, Line B was extended to Carlos Pellegrini station. The line was finally completed on 1 December 1931 when the subway reached the Leandro N. Alem station. These three sections were located below Corrientes Avenue, including 19 curves and 13 stations. Depending to the depth of the line, some sections were constructed using an open trench (cut-and-cover method) or gallery or tunnel. The open trench approach was used in constructing the Federico Lacroze, Dorrego, Canning (now Malabia), Río de Janeiro (now Ángel Gallardo) and Medrano stations. The tunnel at Maipu Street reached a maximum depth of 17 metres. Underneath the Rancagua (today Los Andes) park in Chacarita, a workshop and a 10 track garage (with capacity for 110 cars) were built. Lione B had escalators and turnstiles for the payment of coin-operated service, initially manufactured in the United States, formerly controlled by guards. Line B is deeper underground than Line A, and like it, each station was decorated with friezes of characteristic colours. An underground link with the Mercado Central de Abasto (a wholesale fruit and vegetable market) was opened on 12 July 1933, through which goods wagons with freight from the Ferrocarril Central de Buenos Aires (Buenos Aires Central Railroad) would arrive, driven by electric locomotives. This service ceased after a fire occurred on the link on 27 November 1952. The line always had an automatic light signalling system. In 1980 the mechanical stop-gear devices were replaced by magnetic induction devices, and in 1998 they were finally replaced by an electronic system with Automatic Train Protection (ATP). The original tracks were replaced, and a new automatic signal system with automatic train protection was installed and the transformers were changed to ones that did not contain PCBs , a carcinogenic chemical. The modernisation carried out from 1996 by the private concessionaire Metrovías brought about a radical change in the appearance of the stations, covering the walls of both the platforms and the halls with asphalt-type material painted black and ochre in most cases, except for Callao and Carlos Gardel which were decorated with white tiles with black veins. As a result, the previous coloured friezes that embellished the stations and gave them their characteristic touch were covered. On