Ever since the universal adoption of the alternating current system for power transmission, there has been a requirement for the conversion of alternating current to direct current for many industrial and domestic purposes.

Examples of Mercury Arc Rectifier applications include Traction, Battery Charging and Cinematographic Arc Lamps.

There are many ways in which this can be achieved such as using semi-conductor diodes, liquid rectifiers, rotary converters and synchronous converters and thermionic valves.

One other method of conversion from alternating current to direct current is the mercury arc rectifier which works on the principle that ionised mercury vapour will conduct an electric current unilaterally.

Because of its reliability, simplicity and lack of maintenance requirements the mercury arc rectifier became the most popular method of providing direct current from the AC mains until the introduction of modern semi-conductor diodes.