Professional Q22 Audio Interface Sound Card With Monitoring Electric Guitar Live Recording Audio Extractor For Studio, The MONO key switches between mono and stereo: 1. The unpressed state is the stereo state, indicating that the left and right output signals are different. 2. Press the state to mono state, indicating that the left and right output signals are the same; (3) HI-Z key: suitable for high impedance instrument input, when connecting a guitar, use the 6.3 jack and press the "HI-Z" button; (4) 48V Phantom Power: For 48V condenser microphones and XLR jacks only. 1. When you use a 48V condenser microphone, please use the XLR interface and press the "+48V POWER" button on the rear pan When using a dynamic microphone, please do not p "+48V POWER"; Packing list: 1 x Q24 professional sound recording card 1 x USB cable 1 x instruction