I dont know how to work this unit. I've pressed all the buttons and they seem to function.

except the iPod button doesnt seem to make a change on the screen. I dont know if needs an iPad to do so. The knob is missing but the volume can still be changed. The knows I looked on Google were 14$ unsure the shipping or the stock they have though. It has mounting plates on the side as well. I hope you love the item if you have any questions please reach out.