In the rest position the platinum tips of the two switches are in contact with the mercury and if the two circuits are closed, the current goes through the primary coil and the electromagnet. The core of the electromagnet is magnetized and attracts the mobile plate, thus lowering the arm from which it is suspended; the other arm rises, interrupting the contact between the platinum tips and the mercury in the two switches. The current in the primary coil is sharply interrupted; but since the electromagnet is also interrupted, the soft iron core no longer attracts the plate. The elastic reaction of the copper reed brings the lever to the rest position and the two circuits are once again closed.
As long as the generators are connected the process continues with a frequency depending on the elastic characteristics of the copper reed, the mass of the counterweight and the height at which it is set.
The layer of alcohol above the mercury attenuates the making current and the spark and, besides reducing the oxidation and deterioration of the platinum tips, it makes the interruption quicker and the tension in the secondary coil higher. The performance of the device can be further improved by deriving a condenser at the extremities of the main switch.