1It adopts wireless transmitting and receiving technology, without any cost, and it can be used directly after installing the battery. 2Use environmentally friendly lithium batteries (Included) and 9V batteries (Not Included), which can be removed after use. 3The sound is clear, high sensitive and clear, and the sound can be heard clearly even a few meters away from the transmitter. 4Open ground can be used at a straight line distance of more than 500 meters, and residential buildings can be used at a distance of about 50300 meters depending on the situation. 5The dedicated highsensitivity receiver, the frequency is not in the public range, other equipment can not receive, it has a strong confidentiality. Item Type: Wireless TransmitterMaterial: ABSReceiver Working Voltage: 3.7VReceiver Working Current: 20-30maTransmitter Working Voltage: 9VTransmitter Working Current: 15-40maBuilt-In Battery: 890mah Lithium Battery BL-5B 1 x F-908 Receiver1 x F-908 Transmitter1 x Headphone1 x USB Connection Charging Cable1 x Manual When the channel is disturbed, after removing the battery 5 seconds, the software will automatically reset to channel 14 after reinstalling the battery, and it can be used normally. (The transmitter is transmitted on channel 14)