-PRECISE MEASUREMENT: Equipped with a built-in electromagnetic radiation sensor, which can display the radiation value on the clear LCD digital display after processing by control micro-chip. Testing magnetic field radiation with optional units mG/µT, the electric field with unit V/m. -SOUND-LIGHT ALARM: When the testing result exceeds the value(0.4µT (4mG) or 40V/m), the screen will turn red and the indicator will be flashing, and the buzzer will alarm. If you?re testing some quiet areas, you can close the buzzer first, avoid disturbing the others. -MULTIFUNCTION: Testing average or peak value(Maximum) reading, and one key hold the data for a view. Large and back-light LCD is clear for viewing. Auto power off after 5 minutes without operation. -WIDELY APPLICATIONS: Mainly used for testing TV, computer, printer, microwave oven, refrigerator, cell towers, for low-frequency home appliances, and ghost hunting, etc.