On Jan. 31, American technicians abandoned a secret listening post and radar station on a slope above Beshar. But they left their equipment on -- and apparently it's still working.

Reporters who went to the site Monday found the complex equipment still humming, pulsing and clicking. Iranians at the post said that they had made no effort to disable it and that it seemed to be working automatically.

"We don't know how to turn it off," Hussein Ahmadian, Iranian logistics supervisor at the base said. "We're just going to let it run until someone in Tehran tells us what to do with it."

European experts have said that the Beshar base is one of seven major outposts built by the United States along Iran's nothern frontier to monitor Soviet space launches and listen in on Soviet radio transmissions.

The Beshar facility consists of four major items:

A command center built into a hilltop.

A radar antenna inside a 30-foot-high white dome.

A radio-monitoring device atop a steel tower.

A relay station for communication with U.S. satellites.

A steel door to the command center was still secured Monday by a combination lock with five blank buttons.

"They never let us watch when they [the Americens] pressed the buttons for the combination," Ahmadian said. "We haven't tried to get in." One Iranian employe was told by an American that the door was dooby-trapped.

There is a brass button that apparently rings inside the windowless command center. No one has answered it since Jan. 31, when a convoy of cars took the last Americans working here to Besharhs airport for evacuation.

Outside the wall, a series of big Climatol air conditioners issued a steady sigh. The unmanned requipment within remains climate-controlled.

Above, where the radar dome sits, there is the hum of electronic life. The unit inside aparently is still scanning the skies.

Atop a small steel platform stands another piece of equipment, identified by a plate on its side as a "pedestal model 310," a product of Scientific Atlanta Inc., which the Iranians said was a listening device. It has four 8-foot arms studded with quilllike protrusions. The arms come almost together at the front. It points toward the Caspian Sea and Russia. It hums.

Nearby is a dish-shaped device 15 feet high. It points straight up, and it also hums.

"All this runs on Beshar electricity," Ahmadian said. "But if we turned off the power, there are generators there which cut in automatically to keep things going."

Ahmadian is bearded, fluent in English and bluntly anti-american -- a popular trend in Iran lately.

"Besides," he said, "we don't know who will get the equipment. Maybe Iran well sell it to someone. Maybe we will use it. It might hurt the machinery if we turned off the electricity."

The Beshar base is near the southeast corner of the Caspian Sea about 47 miles from the Soviet border.