1. It can transmit long-distance one-way calls (two sets of duplex intercoms need to be purchased) or transmit audio signals such as mobile phone mp3, and receive audio signals at the receiving end. 2. The basic principle of using infrared laser to transmit sound is to convert fluctuating sound into red laser, then the laser vibration signal is received in the photodiode receiver of the receiver circuit, and the signal is demodulated to achieve sound restoration. 3. The transmission distance can reach 50-100 meters and can be used to manufacture long-distance wireless speakers. Series:Laser Wireless Audio Transmission Kit Model:Laser Wireless Audio Transmission Kit Fun Electronic Production DIY Electrical and Electronic Teaching Training Parts Application:Laser Wireless Audio Transmission Kit Electronics Series Electronic Technology Package:Parts Colour:Green Material:Plastic Size:4x2.2cm Package Contents: 1 * laser wireless audio transmission kit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.