Railway track section safety monitoring circuit - uses track coils interfaced to relay via transformer with saturation characteristic

摘要

A safety circuit (1) is used for monitoring sections of railway track using track circuits. It has a track choke designed according to the track monitoring voltage frequency. The choke primary windings are connected between the tracks. The track monitoring voltage is fed via secondary windings to an alternating current relay energised if the section is free. It prevents faulty indication of a free section arising from transient drive current variations with asymmetric choke loading. The relay is connected to the choke secondary winding via a special transformer with a linear characteristic up to a given voltage above which it saturates.