38mm-Diameter Linear Fluorescent Lamps
(also called T12)
They are the linear fluorescent lamps with the largest diameter. They are the earliest fluorescent tubes designed. Most lamps of this type that are available now are made with halophosphate phosphors and argon as the gas filling.
Performance: They are the least efficient fluorescent sources.
Applications: They are no longer used in new installations where they have been replaced by 26 mm diameter lamps.
Lifetime: 20 – 140 Watt
3000 – 4100 Kelvin
60 – 85
45 – 100 lm/W (typical: 70 lm/W on electromagnetic gear)