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; options include purchasing or building oneavailable through online sources; 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: The package includes only the items listed above; other products are not included. Note: Lighting reflections and differences in display screens may cause slight variations between the color of the item in the image and the actual product. Measurement may vary by +/- 1-3cm.