Mercury switch

These relays use electromagnetic coils to pull steel sleeves inside hermetically sealed containers.

When the switch is tilted in the appropriate direction, the mercury touches a set of contacts, thus completing an electrical circuit.

Tilting the switch in the opposite direction moves the mercury away from that set of contacts, breaking that circuit.

Some electrificators in Croatia also adopted this system, e.g. Alojz Domislovic his successor Luka Ivandija, and later Ivan Bosilj.

Work performed in confined space (such as a welder inside a tank) raises special safety concerns.

Electrically driven attitude indicators typically use mercury switches to keep the gyro axis vertical.

The bimetal spring had to move further to overcome the weight of the mercury, tending to hold it in the open or closed position.

The mercury also provided positive on-off switching, and could withstand millions of cycles without contact degradation.

[8][9] Mercury tilt switches can be found in some bomb and landmine fuzes, typically in the form of anti-handling devices, for example, a variant of the VS-50 mine.

A metal ball and contact wires can directly replace it, but may require additional circuitry to eliminate switch bounce.

In the United States, the Environmental Protection Agency (EPA) regulates the disposition and release of mercury.