a relay box having a carrier plate 2 and a plug - in module 5 is disclosed . a conductor to be switched is brought into electrical contact with a relay 4 through the plug - in module 5 and a plug contact arranged in the plug - in module 5 . the relay is plugged both into the plug - in module 5 and into the carrier plate of the relay box through plug contacts . because of the modular arrangement , increased flexibility is possible when using a prefabricated carrier plate having terminal positions provided for a plurality of relays .