A 3-way lamp, also known as a tri-light, is a lamp that uses a 3-way light bulb to produce three levels of light in a low-medium-high configuration. A 3-way lamp requires a 3-way bulb and socket, and a 3-way switch. Unlike an incandescent lamp controlled by a dimmer, each of the filaments operates at full voltage, so the color of the light does not change over the three steps of light available. Certain compact fluorescent lamp bulbs are designed to replace 3-way incandescent bulbs, and have an extra contact and circuitry to bring about similar light level control.