... .Medical Materials, (environmental protection) 8.Dual channel for two car audio sources9.Compatible with car entertainment, PC, TV, DVD, IPOD, MP4 ... impedance: 32Ω±15%4) Effective range (maximum): about 10 meters5) Audio model: stereo6) S/N ratio: ≥60dB7) Channel separation: ≥40dB8) Frequency ... : 30 ~ 20,000Hz9) Power supply: 2 AAA battery car Infrared wireless headphone