Abstract
When a couple of electric currents flows in opposite direction in a pair of windings of a relay having two pairs, the magnetomotive force due to electric current flowing in those windings will be balanced, and in result the relay does not operate.
But, when one of the electric currents flowing into each winding will be stopped because of the fault of outside circuit, the balance mentioned above will be broken and the relay will be operated.
When four fire detector circuits are connected to each winding to maintain balance in ordinary case, a breaking of the wiring to fire detectors will be indicated directly by the operation of the relay, as soon as it arises.
In such way we can supervise four circuits by means of a relay. In this report the design of a receiving board of fire alarm device with such a new method of supervision is detailed.
