Feature: 1. It adopts wireless transmitting and receiving technology, without any cost, and it can be used directly after installing the battery. 2. Use environmentally friendly lithium batteries (Included) and 9V batteries (Not Included), which can be removed after use. 3. The sound is clear, high sensitive and clear, and the sound can be heard clearly even a few meters away from the transmitter. 4. Open 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 50‑300 meters depending on the situation. 5. The dedicated high‑sensitivity receiver, the frequency is not in the public range, other equipment can not receive, it has a strong confidentiality. Specification: Item Type: Wireless Transmitter Material: ABS Receiver Working Voltage: 3.7V Receiver Working Current: 20-30ma Transmitter Working Voltage: 9V Transmitter Working Current: 15-40ma Built-In Battery: 890mah Lithium Battery BL-5B. Package List: 1 x F-908 Receiver1 x F-908 Transmitter1 x Headphone1 x USB Connection Charging Cable1 x Manual Note: 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)