Sunlight and a fence are visible through one, but through others she sees electronic trails that have been kept for her of neighbors coming and going during the early morning.

可以从一个窗口看到阳光和围栏，但是从其他的窗口她看到为她保留的邻居在清晨来来往往的电子小径。

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Last year, the department pulled the plug on a billion-dollar initiative, known as SBInet, after concluding that the troubled "electronic fence" involving cameras, radar and other devices would be unable to provide the unified border-monitoring system once envisioned.

WSJ: Battlefield Blimps to Patrol U.S.-Mexico Borders