[Southack]

"Electronics monitoring approach to fence...fence...road...fence...electronics monitoring 100 yards inside US border...and UAVs overhead would be a barrier in depth in my view."

Understood, except that monitoring isn't a barrier.

[Jeff Head]

If it monitors those who infiltrate past the physical barrier...and leads to them being apprehended...IMHO it becomes a part of a barrier system in depth. Or call it a Border Enforcement System or some such

But, we can nitpick on and on. The idea that an electronic barrier can be put in place is one that would be best served only, IMHO, when it complimented a good strong physical barrier like the double fence.