This Mel Meter has seven features in one device. The MEL-8704R-REM-EMT-SDD has a self calibrating SDD, Shadow Detection Circuit alarm with ascending and descending tones for intensity. The 5 step sensitivity can be adjusted based on preference and circumstances. Electromagnetic magnetic fields (EMF) in this Mel Meter can only be influenced by materials with conductive properties determined by the types of atoms with highly mobile electrons. The response to the EM field is directly proportional to the REM field disturbance activating the alarm and LED lights. If the source is stronger, the audible and visual response will be greater. This feature does not pick up Radio Waves, AC/DC EMF or any sources that can lead to false positives. Other features of this Mel Meter are ATDD hot and cold spot temperature variations, a programmable REM antenna, a high intensity red flashlight and a star pattern laser projector. If using as a hand held meter, keep hands and fingers at the bottom of the meter.