SOX Sodium, LPS or low pressure sodium lamp warming up. The lamp gradually turns from red to orange as the neon discharge warms the sodium metal up Stock Photo - Alamy
35W BC SOX lamp - Enfield Electrical
Thorn EMI SOX/H 6W
File:SOX lamps (not my image) - Coppermine - 19716.jpg - Roader's Digest: The SABRE Wiki