These bulbs offer three levels of illumination from a single socket, achieved through two separate filaments within the bulb. Each filament provides a different level of light output, and a third setting illuminates both filaments simultaneously for maximum brightness. For example, a bulb might offer 50 watts, 100 watts, and 150 watts as its three levels.
This type of lighting provides flexibility in setting the ambiance and conserving energy. Users can select the appropriate brightness for the task at hand, reducing energy consumption when less light is needed. Historically, these bulbs were a common solution for achieving varied lighting levels before the widespread adoption of dimmer switches and other technologies.
