Joyo JW-02 Digital Wireless Transmitter and ReceiverJW 02 features 4 channels, when several sets of JW 02 are being used simultaneously, you can choose different channels on your own to avoid interference. If the red light flashes after you switch on the transmitter or the receiver, it indicates low battery, please charge it in time with the USB cable. Signal distortion<0. 04%, Plug and play, user friendly