The invention discloses a two-
machine hot standby switching circuit. The two-
machine hot standby switching circuit comprises an isolating circuit, a switching
interlocking circuit and an active / standby indicating circuit, wherein the switching
interlocking circuit comprises two relays, each
relay comprises three contact switches, one of the three switches is normally closed and the other two of the three switches are normally open.
Isolated system A active striving signals are connected to a first end of a coil of a
system A
relay through the normally closed switch of a
system B
relay, and a second end of the coil of the
system A relay is connected with a system A
control power supply;
isolated system B active striving signals are connected to a first end of a coil of the system B relay through the normally closed switch of the system A relay, and the second end of the coil of the system B relay is connected with a system B
control power supply; system A active / standby indicating signals are output to a system A and a system B and system B active / standby indicating signals are output to the system A and the system B through the normally open switches of the system A and the system relays. The two-
machine hot standby switching circuit has the advantages that the circuit is simple, the quantity of the used relays is small and the cost is low; the
circuit reliability is high and the isolation of the two systems is realized.