Highly sensitive microphone amplification, ALC automatic level control, up to 1000 times amplification, can amplify weak sounds, directly drive headphones for listening, and can be connected to mobile phones for recording, and the interfaces are all 3.5mm; Built-in lithium battery, which can be charged using a mobile phone charger. It can be used continuously for 20-30 hours when fully charged; To achieve good results, you need a high-directional microphone. You can make your own or buy one. Please search online.<br><br>Input and output interface: 3.5mm; Mobile phone interface: 3.5mm four-pole Microphone gain: 40db/60db switch Headphone amplifier power: 105mwx2/16 ohms Built-in lithium battery, capacity 300mah Power interface: 5V socket specification: 3.5x1.35 size: About 6.3 x 5.2 x 2.2cm Material: plastic+metal colour: black<br><br>Package Contents: 1 x amplifier 1 x Charging Cable 1 x phone connect cable<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.