Under certain conditions, mechanical relays can not be used. It has extremely fast switching, mechanical noise, which irritates office workers, capacitive and inductive loads, which burn off disconnected contacts or unwanted electrical interferences and contact jams characteristic of mechanical relays. In this case, electronic relays are used. These reels WAGO are manufactured in different casing up to 5A current, there are versions where 6mm housing has 2 separate contacts. When choosing a hard drive, you need to know not only the control voltage, but also the voltage that is switched.