John removed a field strength meter from one of the bags and activated it. The microwave energy levels were less than a microvolt per meter. The energy levels would max out in the millivolt range unless whoever ran security here had disregarded the OSHA safety standards and cranked up the outputs.
Rising out of his crouch, John adjusted the balance of his burdens beneath the poncho. Then stooping once more, John dropped lower until his butt was on his heels, then he duck-walked along the shadow of the near bank. He moved slowly, for motion detectors were more sensitive to a rapid change of field patterns than to a gradual change.
He kept the field strength detector close to his face so it would be readable and to keep its metal parts beneath the cover of his poncho hood.
The field strength rose rapidly as he neared the fence.
Someone had disregarded safety standards. When he stopped at the base of the grate, the energy levels had peaked at nearly a volt per meter, far above normal safety levels. Someone wanted to make sure any movement was detected. If it hadn’t been for his makeshift cloak, John wouldn’t have been able to get within ten feet of the fence.
Moving the detector along the grating, John was thankful to find that the metal itself was uncharged. That meant no electrification and no capacitance sensors. He could touch the grating without setting off an alarm.
John pulled a large rock next to the grating and braced his feet in the snow. He pushed against the grating. It moved, but only a fraction of an inch.
Well, he hadn’t expected it to be easy.
Bracing his back against the grating, John clasped both hands around bars and shoved against the snow-covered sand. As he strained, the heavy grating began to move.
His gaze fell on something he hadn’t noticed in the deep shadows at the edge of the grating. He froze and then slowly let the grating return to its original position.
Moving toward the object, he quickly saw it was a tiny position indicator, a limit switch that closed when the grating moved past a set point. If he had opened the grate another inch the switch would have triggered.
The switch was mounted on a metal plate set against the unmoving bars at the grating’s edge and its tiny roller was compressed by another plate mounted on the grate itself. A pair of light gauge wires, covered with thick insulation, ran from the back of the switch to a nearby junction box.
Which was it? Normally open or normally closed? He guessed that it was closed as long as the grating was closed. Then opening the grating would interrupt a circuit and close a relay back at security’s command post.
John rummaged through his bags until he found the small Fluke multi-meter. He activated it and pressed its leads against the tiny wires. The readout showed no voltage. That was one indication that the switch was closed. He changed the setting to microvolts and looped one of the leads several times around one of the wires. This time he detected a slight electric field, indicating a current flow in the wire.
He had guessed right. The switch was closed and a relay somewhere was sending a signal down the wires and through the switch.
That was easily handled. John returned the multi-meter to his bag and took out a short piece of wire with an alligator clip at each end. He attached the clips to each of the tiny wires, pressing them in to make sure they penetrated the insulation.
Moving back into position, he strained against the grating until it slowly moved back and away from him. The pressure brought the fire back to his shoulder. It burned with every inch the grating moved until his eyes involuntarily teared.
He stopped and held the grating about eighteen inches off the ground. Using his left foot, he maneuvered the rock into position and then slowly released the bars. The heavy grate pressed the rock into the arroyo bed about three inches before coming to a stop.
It didn’t leave much room, but John didn’t think he had the energy to lift the grating again. It would have to do.
He rested for a moment, both to keep from sweating and to restore his energy. There was going to be plenty to sap his reserves without letting them get prematurely low. John pushed his bags under the grating then slid under, stopping only once to free the edge of his poncho. John rose slowly on the other side, then picked up the bags again, and took out his meter.
The field strength was still too high. There must be another detector. It took him nearly a minute to find it mounted on a pole twenty yards farther down the arroyo. Still duck walking, John went another fifty feet before the energy levels were down to the point that he thought he was totally clear of the motion detectors.
Standing was nearly as painful as the long walk. Muscles protested and tried to cramp. He had to stretch them before continuing.
Continuing cautiously down the arroyo, he kept a close watch on the meter. There was always the possibility of multiple layers of protection.
He guessed right.
Twenty yards later the meter picked up another source. John slowed and looked for the transmitter. After a few minutes of fruitless searching, he gave up and started forward again. The field strength continued to rise.
He moved the meter, sniffing out the source, until he determined that it was coming from something buried in the sandy floor of the arroyo. It didn’t appear to be part of
