gramophone turntable<unk> s play an important role in the study of stresses on machinery in motion, and in many other forms of research. Bright<unk> s are able to overpower ambient lighting and make stop-motion effects apparent without the need for dark ambient operating conditions. They are also used as measuring instruments for determining cyclic speed. As a timing light they are used to set the ignition timing of internal combustion engines. In medicine,<unk> s are used to view the vocal cords for the diagnosis of conditions that have produced dysphonia (hoarseness). The patient hums or speaks into a microphone which in turn activates the<unk>  at either the same or a slightly different frequency. The light source and a camera are positioned by endoscopy. Another application of the<unk>  can be seen on many gramophone turntables. The edge of the platter has marks at specific intervals so that when viewed under fluorescent lighting powered at mains frequency, provided the platter is rotating at the correct speed, the marks appear to be stationary. This will not work well under incandescent lighting, as incandescent bulbs don't significantly strobe. For this reason, some turntables have a neon bulb or LED next to the platter. The LED must be driven by a half wave rectifier from the mains transformer, or by an oscillator. Flashing lamp strobes are also adapted for pop use, as a lighting effect for discotheques and night clubs where they give the impression of dancing in slow motion. The strobe rate of these devices is typically not very precise or very fast, because the entertainment application does not usually require a high degree of performance.
Stroboscope
Stethoscope
Otoscope
Keratoscope
Fetoscope
Rhinoscope
Endoscope
SurgiScope