Compact fluorescent Plug-In light bulbs have either 2 pins or 4 pins.
Each 2-pin lamp has an internal starter and is designed for preheat, magnetic operation.
The 4-pin lamps are designed for electronic ballast operation and are dimmable. These lamps have no internal starter; starting the lamps is a function of the ballast.
The following illustrations show some of the most popular Compact Fluorescent Plug-In bases:
|Base||Top Down||Lamp Profile|
|2-Pin 1-Tube CFL|
|2-Pin 2-Tubes CFL|
|4-Pin 1-Tube CFL|
|4-Pin 2-Tube CFL|
|4-Pin 3-Tube CFL|
|4-Pin 4-Tube CFL|