The first electrified main line in the Soviet Union was a section of the Trans-Caucasian Railway, which runs from Baku to Batumi in what is now Georgia and Azerbaijan. The electricity system chosen was direct current with a voltage of 3,000 volts, which is still the dominant electricity system in large parts of the CIS countries. Since there was still no domestic experience with the construction of electric locomotives, several countries looked around for suitable machines. The contract was initially awarded to General Electric from the USA, with whom a contract was signed for the delivery of two complete electric locomotives and six others without traction motors.
The locomotives became the class С10 (Cyrillic for S10), which was later renamed С. The letter S stood for the operational area at the Surami Pass. They each stood on two three-axle bogies, each with three 340 kW traction motors. The six most recently delivered machines had equally powerful traction motors from Soviet production. The locomotive body was angular and provided with a platform at both ends, on which the clearly visible sockets for the multiple control were attached. This appearance was also shared by the later Soviet electric locomotives over the next few decades.
Since General Electric had also sent the construction plans to the Soviet Union, they began to build them again in 1932 as the class СС. The second S gave an inference that they were from the Soviet Union. The 21 series examples received the same traction motors as the last six locomotives of the С series, while the mechanical part was manufactured at the Kolomna plant. In 1952, these locomotives, as well as the first two locomotives of the previous series built in the USA, were modernized. They received more powerful traction motors, each with 400 kW, as they were already used in the ВЛ22М. They were now approved for 80 km/h and were listed as the СМ (SM) and ССМ (SSM) series. Their retirement took place between 1968 and 1974.
