Highly sensitive microphone amplification with ALC automatic level control, up to 1000 times amplification, capable of amplifying weak sounds. Directly drives headphones for listening and can be connected to mobile phones for recording. All interfaces are 3.5mm. Built-in lithium battery that can be charged using a standard mobile phone charger. Provides 20-30 hours of continuous use when fully charged. For optimal performance, a high-directional microphone is recommended. Input and output interface: 3.5mm. Mobile phone interface: 3.5mm four-pole. Microphone gain: switchable between 40dB and 60dB. Headphone amplifier power: 105mW x 2 at 16 ohms. Built-in lithium battery capacity: 300mAh. Power input: 5V. Socket specification: 3.5x1.35mm. Dimensions: approximately 6.3 x 5.2 x 2.2cm. Material: plastic and metal. Color: black. Package Contents: 1 x amplifier 1 x charging cable 1 x phone connection cable Note: Light reflection and different display settings may cause slight color variations between the image and the actual item. Measurement error allowance is +/- 1-3cm.