Sam Fisher- IDing Pressure Plates

Unlike the wall he'd photographed on the lakeside of the property, this one was higher, perhaps six feet, and topped with shards of jagged ceramic embedded in mortar. This was of little concern to Fisher; the shards would barely scratch his RhinoPlate. What concerned him was what he saw when he studied the wall with the Tridents' EM mode: Every third brick in the row just below the shards was pulsing with energy. The Tridents' EM wasn't sophisticated enough to tell him the precise nature of the energy, but experience told him radio waves. Fisher zoomed in and switched to night vision, then infrared. The former showed no signs of cameras or directional microphones; they were perfect replicas of weatherworn bricks. Infrared, however, showed that each third brick was warmer than its neighbors, which suggested it was being fed electricity. So: not visual, not auditory. Pressure or tremble, Fisher thought. If something of roughly human weight climbed the wall, the faux bricks would send a signal--probably to a monitoring center in the house.

- Conviction, Chapter 10