Patrolling the streets of Kabul and Afghanistan's rocky countryside, U.S. troops driving combat vehicles use radios that were installed and tested in the Lowcountry.

Surveillance equipment, weaponry and even seat belts are put into the heavy-duty trucks at a nondescript, heavily guarded North Charleston warehouse on the former Naval base.

The facility, staffed by private contractors, has turned out 5,000 of the lightweight combat vehicles, a milestone that warranted not only a celebration but also a visit from the nation's highest-ranking military officer.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, visited the warehouse Thursday, touring the assembly line of khaki-colored vehicles and thanking employees who work there.

"It's such a critical part of our capabilities as a military," said Mullen, who stood rigid at a podium, dressed in blue camouflage fatigues.

"There isn't a trip I take into the theater where some young soldier or Marine won't say to me, 'Keep those MRAPs and ATVs coming. They save our lives. Tell whoever you see that's involved in this "Thank you." ' So that's part of the message I bring as well."

After speaking, he walked through the crowd of workers, patting backs and shaking hands.

Roughly 1,200 employees work on the vehicles at three facilities around the state.

Science Applications International Corp., a Virginia-based defense giant, won a multimillion contract to outfit the vehicles.

The trucks arrive from a Wisconsin manufacturer ready to drive but empty inside.

Workers on Thursday sat on top of vehicles, installing a remote-controlled surveillance and weapons console. They hung from the vehicles' sides, bolting on plates and accessory parts.

By the time the vehicle is finished, the inside is crowded with computer screens, control boards and special equipment. Cords and buckles dangle from the ceiling.

Aside from a button to activate the windshield wiper, the dashboard's icons are cryptic and unfamiliar.

Space and Naval Warfare Systems Center Atlantic, or SPAWAR, oversees the operation.

SPAWAR's North Charleston campus is one of few places in the country that can properly test a combat vehicle.

That's because a key part of the test involves blocking communication signals, which requires sophisticated equipment.

They also conduct the tests in a remote part of the base, far away from local residents to avoid unintended consequences.

"We don't want to open up peoples' garage doors," said SPAWAR spokesman Jack O'Neill. "We don't want to block their cable (television channels)."

Congress approved money to buy 8,000 of the vehicles, after buying more than 16,000 heavier vehicles for the military's Iraq mission.

Most of the lighter vehicles are shipped overseas. Military officials used to fly them over on C-17s, back when troops needed the modified vehicles urgently.

Proudly, technician Angel Moore-Stokes of Summerville screwed antennas onto the 5,000th vehicle. She said that knowing the vehicle will protect U.S. troops keeps her motivated.

"It could be your cousin in there," she said.