Fangrui Product Details 1. Asing S16 2.4g Wireless Voice Amplifier With Headset Microphone For Teachers Tour Guides 2. Wireless Zero-binding, Upgraded To Suppress Howling, Intelligent Noise Reduction, Clear Original Sound, And Better Sound Quality 3. 2.4g Wireless 30-meter Transmission, Strong Anti-interference And No Cross-frequency, Stable Signal And Continuous Connection 4. Skin-colored Microphone, Invisible To Wear, No Fatigue And No Pain In The Ears After Wearing For A Long Time 5. The Amplifier Has A Built-in Large Speaker With Loud Sound. 6. Frequency Range: 2400mhz-2483mhz 7. Working Distance: 30 Meters 8. Battery Type: Rechargeable Lithium Battery 9. Battery Capacity: Microphone: 300mah, Amplifier: 2200mah 10. Battery Voltage: 3.5v-4.2v 11. Transmit Power: 3dbm 12. Receiver Sensitivity: -89dbm 13. Transmitter Sensitivity: -52+-3db 14. Signal-to-noise Ratio: 90db 15. Duration Of Use: 8 Hours Of Continuous Use (amplifier), 8 Hours Of Continuous Use (microphone) 16. Charging Time: 1-2 Hours 17. Overall Dimensions: 57x48x16mm (microphone), Tube Length 150mm, 98.5x89x40mm (amplifier) 18. Weight: 27.5g (transmitter Including Headband) 200g (amplifier) 19. Packing List: 20. Wireless Microphone 21. Voice Amplifier 22. Double-ended Charging Cable 23. Instruction Card 24. Cute Stickers 25. Strap Chain (optional)