Wall Ear Listening Device 
Four audios sections, A. section (200Hz), B. section (400Hz), C. section(800Hz), D. section (1200Hz), adjustable according to the spot situation.
The highest frequency enlarged can be 50000 times ??
Applied for business monitor, and surveillance information collect etc. 
·Power Consumption :10mA
·Battery:AAAX2
·Four audios sections: A section (200Hz) B section (400Hz) C section (800Hz)D section (1200Hz) ·Detector head sensitivity :20uV
·Highest audio multiple enlargement: 50000 times
·Penetration :Concrete wall, reinforcing steel bar wall, wood wall, Metal wall, Glass wall, Brick wall Monitor mode: Earphone, external loud :speaker
·Record mode:Audio output for external recorder
·Working temperature-20℃~50℃
·Weight:140g
·Dimensions84*62*21mm 

Attention:
·2 X AAA battery. If the HI frequency voice, you can lower the volume orchange "Frequency button" to pause the unexpected thing. 
·Insert the voice detector to "detector head connector jack", powered on;
adjust the volume to what you want. Approach the detector to the interface.
Then you should hear the spot voice from the earphone. 
·If you need to recorder, the audio cable is necessary. Put one end to "REC", the other end to "MIC" of the recorder's.