Cold backup double-machine switching circuit

The invention discloses a cold backup double-machine switching circuit, which comprises a host machine part and a backup machine part corresponding to the host machine part on circuit structure, wherein the host machine part comprises a host machine power supply circuit, a host machine switch relay and a host machine secondary power supply converter which are connected in turn; the output of the host machine secondary power supply converter is connected with the input of a host machine CPU controller and the input of a dog bite and backup electromechanical circuit respectively; the output of the host machine CPU controller is connected with a switch-off backup electromechanical circuit and is in bidirectional signal connection with a host machine cold/hot start mark circuit at the same time; and the output of the switch-off backup electromechanical circuit is connected with a host machine remote measuring switching circuit. The host machine switch relay and the backup machine switch relay are connected with direct instructions respectively, wherein the direct instructions comprise host-on backup-off instruction and backup-on host-off instruction; the output of the dog bite and backup electromechanical circuit and the output of the switch-off backup electromechanical circuit are connected with the backup machine switch relay; and the output of the dog bite and host electromechanical circuit and the output of the off host electromechanical circuit are connected with the host machine switch relay.