Applies to lampholders with Edison thread E14, E27 and E40, designed for connection to the supply of lamps and semi-luminaires only. Also applies to: -switched-lampholders for use in a.c. circuits only, where the working voltage does not exceed 250 V r.m.s; -lampholders with Edison thread E5 designed for connection to the supply mains of series connected lamps, with a working voltage not exceeding 25 V; -lampholders with Edison thread E10 designed for connection to the supply mains of series connected lamps, with a working voltage not exceeding 60 V; -lampholders to be used indoors or outdoors in residential as well as in industrial lighting installations.