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Figure 5.3. Fluorescent tube diameters.
U-shaped fluorescent tubes offer an
alternative configuration, being shorter and with the lamp cap(s) at one end. See
Figure 5.4. Mod-U-Line tubes can fit into 600 mm x 600 mm ceiling luminaire,
compared with 600 mm x 1200 mm luminaire for straight tubes. The biaxial shape has a single lamp
cap with either two or four pins - GE trademark BIAX. More information on these lamps is given in
the Compact Fluorescent Lamp section.
Figure 5.4. U-shape fluorescent lamps.
Circular fluorescent lamps give
another option. See
Figure 5.5 . These have a four pin cap and are available in three different
diameters.
Figure 5.5. Circline range.
Fluorescent Lamp Caps
There are three different types of lamp cap:
-
Single pin
-
Bi-pin
-
Four pin
Bi-pin is the most common and for
straight tubes there are just two versions. See
Figure 5.6.
Figure 5.6. Bi-pin lamp caps.
Single contact caps are used for Slimline tubes which have a special starting circuit. Four
pin caps are used on Mod-U-Line and Circline lamps.
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