||The SOX-Plus lamp was launched by Philips in 1993, with its goal being to extend the group re-lamping interval for low pressure sodium installations from two to three years and allow them to compete better with the longer life SON lamp. Very soon afterwards the same improvements were offered in this lamp from Osram, as well as by General Electric.
In terms of construction, SOX-Plus lamps are virtually identical to their predecessors. For a number of years ordinary SOX lamps had been out-performing their life claims, and rather than simply upgrading the specification, Philips cleverly re-marketed them as apparently superior products under the SOX-Plus name. Since longer life claims were advantageous to users, a higher price and greater profits could be commanded. The higher selling price was needed to counter the terms of the longer warranty, since an increase in the number of claims could be expected. After a number of years when this became widely known, the orginal SOX disappeared and was replaced by SOX-Plus.
This Osram lamp makes use of the same red colour cap as the Philips SOX-Plus to indicate its longer claimed lifetime. At the time of its introduction, the discharge tube top support was changed. The former 2-piece metal construction has been replaced by a single-piece component stamped from metal sheet. In parallel the shape of the domed end of the outer envelope has been changed, having a flat shoulder and dimpled end. The new support is mounted against the flat shoulder and cushioned by four small leaf springs formed into the metal support, to effectively absorb thermal expansion of the hot dischage tube without exerting high forces on the outer envelope or mount construction.