ASiNG S16 2.4G Wireless Voice Amplifier with Headset Microphone for Teachers Tour Guides 1. Wireless zero-binding, upgraded to suppress howling, intelligent noise reduction, clear original sound, and better sound quality 2. 2.4G wireless 30-meter transmission, strong anti-interference and no cross-frequency, stable signal and continuous connection 3. Skin-colored microphone, invisible to wear, no fatigue and no pain in the ears after wearing for a long time 4. The amplifier has a built-in large speaker with loud sound. 5. Frequency range: 2400MHz-2483MHz 6. Working distance: 30 meters 7. Battery type: Rechargeable lithium battery 8. Battery capacity: microphone: 300mAh, amplifier: 2200mAh 9. Battery voltage: 3.5V-4.2V 10. Transmit power: 3dbm 11. Receiver sensitivity: -89dbm 12. Transmitter sensitivity: -52+-3db 13. Signal-to-noise ratio: 90db 14. Duration of use: 8 hours of continuous use (amplifier), 8 hours of continuous use (microphone) 15. Charging time: 1-2 hours 16. Overall dimensions: 57x48x16mm (microphone), tube length 150mm, 98.5x89x40mm (amplifier) 17. Weight: 27.5g (transmitter including headband) 200g (amplifier) Packing list: Wireless microphone Voice amplifier Double-ended charging cable Instruction card Cute stickers Strap chain (optional)