Never heard them referred to as SBML. MBTF was the designation
I used to hear them referred to as.
The integral filament is not efficient as a ballast (and neither
was it an efficient filament as it had to be underrun to get a good
life, and it's in nitrogen atmosphere at not much below atmospheric
pressure, required for the quartz arc tube). The lamps were only
around 20lm/W, which is same ballpark as a modern halogen lamp
and not a lot better than a similar powered regular filament lamp.
They were used for street lighting in the area I grew up, only
because they retrofitted into standard filament lamp housings
and required less relamping at 6000hr life. The old lanterns have
long since been replaced by ones designed for more efficient
HID lamps, and the main market for MBTF lamps vanished many years
Apparently, Chinese manufacturers have started making them again
now, using a halogen capsule for the filament/ballast part, and
they are 30lm/W because the filament can run at standard halogen
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