A German engineer Hein Moeller developed the world's first oil contactor.

What is the purpose of contactors?

A contactor is an electrical device which is used for switching an electrical circuit on or off. It is considered to be a special type of relay.

Who created relay?

American scientist Joseph Henry is often claimed to have invented a relay in 1835 in order to improve his version of the electrical telegraph, developed earlier in 1831.