Abstract: A circuit suitable for the instantaneous starting, continuation, and interruption of current through one or more gasfilled discharge tubes, in particular fluorescent lamps, is described. The circuit and lamp heaters are energized before instantaneous control can occur. One preferred silicon controlled rectifier (SCR) is used with a bridge rectifier. The SCR has the dual role of causing the capacitor to discharge through the pulse transformer, the secondary pulse voltage of which thereby causes the arc to strike immediately upon application of gate current, and then maintianing the lamp current as long as a supply of SCR gate current is provided. A second preferred control device, a TRIAC, is used without a bridge rectifier and again has a dual role of pulse-starting and maintaining current. This type of device is more conveniently arranged to provide for a dimming function as well. Applications include "flashing" advertising signs, general illumination, and signals.

Abstract: A microscope is arranged so that the light from the object under study is directed down through an objective lens and then to a video camera. None of it is diverted to an eye piece or the like. The image can be viewed on a video monitor. There is no clutter of optical equipment above the object, and there need be only enough light to operate the camera.