| 摘要 |
A window generation circuit is provided for gating image signals from an electronically scanned sensor array in a line tracing machine. The window generation circuit includes two shift registers of variable length for measuring intervals of time for setting first and second bounds to a sector scan. The interval of the second register corresponds to the width of the window. Logic circuitry, responsive to the detection of image data, alters the electrical lengths of the registers to enlarge the window in the absence of an image, and restores the original lengths upon return of the image.
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