The key to safety: Plugs and receptacles with a cleverness: The innovative coding of apparatus allows plugs used for Zone 1 to be used in receptacles for Zone 2 and/or for usage with industrial receptacles as well. Hence, plugs and receptacles for Zone 1 can be used anywhere. However, by the same token, the coding ensures that Zone 2 plugs cannot be operated in sockets with Zone 1 coding. That guarantees safety with an enormous flexibility in their usage. Speaking of flexibility: It goes without saying that the plugs of the existing range also fit into the new receptacles.