| 摘要 |
A place scenery is surveilled by a video camera. The image signal from the video camera is converted to data, the data is stored in a memory as a current data and then compared with previous data which was prepared and stored in another memory in a previous surveillance period. The current and previous data is compared and an alarm signal generated when there is a difference between both data. Thereafter the previous data is erased and replaced by the current data in the memory and stored until the next image data is derived from the video camera. The operation is repeated at predetermined time intervals.
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