021 electromagnetic wave/magnetic field detector is not only a high sensitivity electromagnetic wave detector,but also an advanced magnetic field detector.Its digital linear magnetic field detection technology can effectively detect weak magnetic field signals.Compared with the detection technology used in magnetic field detector,the performance of the detection technology is greatly improved,which is very beneficial for the search of the strong wireless magnetic GPS tracker. Magnetic field detection distance up to 200mm Electromagnetic wave detection distance up to 5m 021 adopts magnetic field/electromagnetic wave dual-channel simultaneous detection technology, which does not need to witch back and forth in the magnetic field/electromagnetic wave like ordinary multiple detector. A common detector needs to detect twice, and 021 only needs to detect once, which effectively improves the GPS tracker's detection efficiency. colour: black Material: ABS Package Contents: 1 x Wireless GPS Signal Detector Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.