Nearly half would be a so-called "virtual fence" utilizing high technology sensors and cameras as well as special deployments of Border Patrol agents.

将近一半是所谓的“虚拟围墙”， 使用高科技传感器和照相机以及特别部署边界巡逻队的警卫。

youdao

A source of anger for many lawmakers at the hearing was a U.S.government contract for a so-called "virtual fence" monitoring system along the nearly 3200-kilometer U.S.-Mexico border.

VOA: standard.2010.04.21

And this week along a stretch of border in Arizona, the government is bringing online a test of a high-tech virtual fence.

NPR: Immigration Stalemate Frustrates Arizona

Mr. McCaul says the bungled project called SBInet, which included the virtual fence plan, set back the cause of border security five years.

WSJ: Border-Security Drone Program Off to Rough Start

Tests of the virtual fence didn't lead to nearly as many arrests as designers had hoped, and the lag from sensor detection to transmission of an image to border agents was apparently a big part of the problem.

ENGADGET: Border Patrol's virtual fence canceled for not being as good as a fence