Transfer apparatus for energy sources in railway track circuits

Abstract From the Canadian patent

A circuit arrangement for automatically transferring from a main to a standby source for supplying a variable load network, such as a railway track circuit comprising first and second monitoring channel apparatus to detect the level of the normal output and load current, respectively. Source output varies from normal to low level and load current from low to high level as load network varies between relatively no load and heavy load conditions. The monitor channel detection signals are checked through a logic circuit so that if at least one exceeds a predetermined level indicating the operable condition of the principal source, a registry device is actuated to hold the energy supply leads …