Electrical enclosures made from sheet steel; cases adapted for electronic circuits; cases adapted for electronic equipment; apparatus for linking computers into networks; apparatus for network communication; apparatus for use in communications networks; communication devices for linking computer networks; computer apparatus for use in local area networks; computer apparatus for use with computer networks; computer network apparatus; computer networking apparatus; local area networking apparatus for the switching of data; local area networking apparatus for the transmission of data; network controlling apparatus; network management apparatus; data packet switching apparatus; data switching apparatus; packet switching apparatus; housings for electronic sub-assemblies