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. Compatible microphones can be purchased online. Input and output interface: 3.5mm Mobile phone interface: 3.5mm four-pole Microphone gain: 40dB/60dB switchable 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 in color between the image and the actual item. Measurement allows an error of +/- 1-3cm.