one-to-one or one-to-two 
*.2.4G wireless technology
*.reverberation effect
*.double noise reduction
*.charging chamber
*.omnidirectional radio
*.HD sound quality
*.barrier-free transmission ≥20 meters 
*.powerful and compatible
*.frequency range 20-20KHz
*.signal to noise ratio ≥64DBM
*.strong compatibility
*.battery life 4-5 hours