McLEAN, Va. When the CIA's secret gadget-makers invented a listening device for the Asian jungles, they disguised it so the enemy wouldn't be tempted to pick it up and examine it: The device looked like tiger droppings.

The guise worked. Who would touch such a thing? The fist-sized, brown transmitter detected troop movements along the trails during fighting in Vietnam, a quiet success for a little-known group of researchers inside the world's premier intelligence agency.

The CIA's Directorate of Science and Technology is celebrating its 40th anniversary by revealing a few dozen of its secrets for a new museum inside its headquarters near Washington.

It is accessible only to CIA employees and guests admitted to those closed quarters.