The document specifies requirements for heat test source (H.T.S.) lamps used for carrying out those thermal tests of IEC 598 which primarily check the influence of heat conducted through the lamps cap as well as of convection.
DIN EN 60634:1996 history
1996DIN EN 60634:1996 Heat test source (HTS) lamps for carrying out heating tests on luminaires (IEC 60634:1993); German version EN 60634:1995