Box of 'Kaleeco' two-way porcelain sheathed connectors. Part of the Bob Gray collection of electrical objects.

Porcelain was a popular material for many types of electrical insulators until the 1930s when thermosetting plastics such as Bakelite started to take their place. By the 1930s a greater emphasis on electrical safety meant that cables for industry were enclosed in steel conduit or trunking.