It looks likes it a mini USB port but not sure. What is the intention of that port...hard drive, printer? What have you done with it?
The mini USB port is typically used to restore an Apple TV with iTunes and/or for use in jailbreaking.
usb has 2 types of port "computer end" (type a) and "device end" (type b). and also the different sizes the port on your aTV is a type B, and is only designed to hook to a computer and not another device. the 2nd gen aTV also had this port