||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 by Osram, as well in this lamp from 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 was advantageous to users, a higher price and hence 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 was widely known, the orginal SOX ranges disappeared and were replaced by SOX-Plus.
This GE lamp makes use of the same red colour cap as the Philips SOX-Plus to indicate its longer claimed lifetime. Shortly before its introduction, the discharge tube top support was changed in all GE SOX lamps. The former 2-piece metal construction with ceramic insulator has been replaced by a single-piece component formed from metal sheet. The shape of the domed end of the outer envelope has been flattened to allow the IR coating to extend further over the bend for better thermal insulation. Owing to the elimination of the ceramic isolator tube, a gap has been left in the IR coating to avoid its accidental electrification by coming into contact with the barium getter near the cap.