A mechanical dimming device used to fade in, fade out, or otherwise adjust the intensity of the light from an arc source which cannot be dimmed electronically. Most often found in followspots and automated lights, and any other fixture not using an incandescent light source. Two popular stand-alone units, most often used on HMI Fresnels or HID "Sportlighter" fixtures are the Wybron Eclipse IT Shutter and the Wybron Eclipse Iris IT: See the thread Need a remote douser? for some clever ideas on building one's own video projector douser. Note: A dowser is a person who looks for underground water using divining rods. To immerse with water or to extinguish is to douse.