Lamp caps and holders together with gauges for the control of interchangeability and safety - Part 2: Lampholders (IEC 60061-2:1969 + Supplements A:1970 to Q:1996, modified); German version EN 60061-2:1993 + A1:1995 + A2:1995 + A3:1995 + A4:1996 + A5:1996