Transmitter Radiate Frequency: FM 49.85MHz "Radiate power: max120dB " "6F22(9V) battery, or used AC/DC adopter " Audio input: <<500mV Headphone Size"2450"recharge Li-ion battery , AC/DC recharge adopter Battery recharge life: >>300 cycle Receiver frequency :FM 49.85MHz "Audio frequency response: 80HZ~15KHZ(+/-3dB) " S/N: >>45dB Out put power:>50mW Receiver distance:>40 meter(none impediment)