The TGV (, "high-speed train") is France's high-speed rail service, operated by SNCF Voyages, the long-distance rail branch of SNCF, the national rail operator. It was developed during the 1970s by GEC-Alsthom (now Alstom) and SNCF. Originally designed as turbotrains to be powered by gas turbines, the prototypes evolved into electric trains with the 1973 oil crisis. Following the inaugural service between Paris and Lyon in 1981 on the LGV Sud-Est ("LGV") (, high-speed line), the network, centred on Paris, has expanded to connect main cities across France and in adjacent countries on combinations of high-speed and conventional lines.