1Relay type 4-channel o source selection, switching, input selection board (actual 1-4 way adjustment). 2You can switch CD/DVD/PHONO/AUX 4 sets of input, and set LED lighting tube for switch shift indication. 3The relay used is well-selected relay , durable and reliable. 4Motherboard and switch connected with cable long 30cm with knob. 5With 1.6mm thick double-sided tinned printed circuit board, the most direct and most fidelity switching of the sound source, the board is stereo two-channel. Item Type:o Switch Input Board Single Power Voltage:AC12~15V Development Board Size:43.5 x 43.5mm / 1.71 x 1.71in Installation Hole:33.5 x 33.5mm / 1.32 x 1.32in Motherboard Size:105 x 43.5mm / 4.13 x 1.71in Installation Hole:94 x 33.5mm / 3.7 x 1.32in Base Hole Interval:13mm / 0.51in border: 1px solid000important;}1 x o Source Selection Board1 x Selection Switch1 x Connection Cord1 x Knob2 Bag of Accessory