oscilloscope əsĭl´əskōp˝ [key], electronic device used to produce visual displays corresponding to electrical signals. Displays of such nonelectrical phenomena as the variations of a sound's intensity can be made if the phenomena are converted into electrical signals. Originally, the display was formed by a moving dot on the screen of a cathode-ray tube. For most applications horizontal deflecting circuits move the dot in a repetitive cycle from left to right, and then, very quickly, back to its starting position to begin the next sweep. If during this process the vertical deflecting circuits move the dot up and down in response to the variations of the signal to be observed, a wavelike picture of the signal appears on the screen. Liquid crystal display screens are now also used, and the image is produced digitally. An oscilloscope is one of the most valuable tools of an engineer or electronics technician.

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