The first successful operational and regular use of the system dates back to 1931, tests having run since 1922. It was developed by Kálmán Kandó in Hungary, who used AC at , asynchronous traction, and an adjustable number of (motor) poles. The first electrified line for testing was Budapest–Dunakeszi–Alag. The first fully electrified line was Budapest–Győr–Hegyeshalom (part of the Budapest–Vienna line). Although Kandó's solution showed a way for the future, railway operators outside of Hungary showed a lack of interest in the design.