- I don't know if this helps, see below from :-
"... The Name of the Lamp indicates they are Tubular compact fluorescent lamps, it goes something like this:
TC: = Tubular compact
D/T: D=Double, T=Triple, S=Single, Q=quad; this relates to the number of U tubes in the lamp.
E or EL: = for Electronic control gear, that is it has 4 pins, as opposed to those for magnetic gear that have 2 pins.
e.g Sylvania call theirs "Lynx DE" for a double U lamp for electronic control. ... "