A guard was standing at the entrance with her hands crossed doing nothing by observing. When she saw me coming she made a few quick steps towards me and signaled me to stop and stand aside for questioning. I felt a bit uncomfortable, first because it was abrupt and I was being singled out, but also because she was behaving like a shepherd dog trying to seize my eyes (which I later understood why). She was very polite and dismissed me after presenting my ID and answering a few short questions.
This got me thinking about the silent perimeters, and how smart it is they were only engaged when triggered. The take home lesson for me was: smart earns respect. They were a step ahead of me and I was responding, not them.