where the NLJD is expected to sweep. This masks the true listening device against a field of false alerts when the many diodes are detected. Such a technique was used in the 1980s construction of the U.S. embassy in Moscow. Thousands of diodes were mixed into the building's structural concrete making detection and removal of the true listening devices nearly impossible. See also Covert listening device References External links Non-Linear Junction Detector Review and Tutorial NLJD Lornet Star 24s GBPPR Non-Linear Junction Detector Homebrew non-linear junction detector project. Detectors