AC track circuit

Abstract

Track circuit is the fundamental method of train detection. The first track circuit, based on a DC technology, has been invented at the end of nineteenth. Over the years, the continuous technological development has enabled to realize track circuits in an increasingly performing way by using AC technology and modulations, but the basic principle for train detection is still the same. An alternative approach is the Axle Counter system, which uses a “check-in/check-out” logic. By comparing the result for the axles counted in a block section with the result for those counted out, it is possible to know the status of the track section (free or occupied).