[With charging interface] - The built-in battery of this through wall microphone can be charged repeatedly, providing 5 to 7 hours of usage time. The machine jack and upward switch knob make it easy to use and adjust. [Applications] - This device can be connected to various devices such as display spectrums, voice recorders, transmitters, and wireless devices. It can detect abnormal noises from heating ducts, fire ducts, water pipes, underfloor heating ducts, automobiles, home plumbing, and more. [Sound sensitivity] - Equipped with high sensitivity metal alignment with headphones, this device offers clear sound quality and detects sound from , , doors, or armor plates. [Easy to operate] - Simply press firmly against doors, , orand adjust the sound with the knob until you hear a clear sound. This device is effective in emitting sound from wooden , bricks, , and doors with efficient noise filtering and faster sound detection. [Strong penetration] - The high sensitivity sensing head and advanced technology allow for increased penetration several times, greatly improving sound quality. Spec: Item Type: Through Wall Microphone Amplifier Material: ABS Amplifier Battery: LithiumBattery (Ship with Inbuilt Battery) Capacity: 100 mAh Sound Input: 32ohm Headphones Probe Sensitivity: -60dB Maximum Voice Frequency Amplification: 13000X Working Time: 5-7 Hours Probe Power Consumption Current: 12mA Use: Can Detect Heating Pipes, Fire Pipes, Water Pipes, Floor Heating Pipes, Automobile Abnormal Noise, Household Pipes Package List: 1 x Through Wall Microphone Amplifier (Ship with Inbuilt Battery) 1 x 3.5mm Earphone 1 x USB Cable 1 x Instruction Manual How To Use: Remove the product and use it