***** ********** *****-The launcher is fixed on the guitar strap to prevent the launcher from turning or falling. ***** *****-Avoid some special guitar interfaces, resulting in U2 can not be inserted directly. ***** *****Avoid eletric guitars with preamp circuit or acoustic guitars with microphone pickup, which are disturbed by transmitters and produce high-frequency noise. ***** *****-Elastic band is fixed with hook-and-loop fastener tape, and firmly hold the transmitter