usb to ethernet adaptor circuit diagram
Those adapters are completely useless. They do not actually convert USB to Ethernet at all; they just connect the four pins of a USB connector randomly to four pins of the RJ45 connector. Plugging a USB device into a network jack using this adapter would not do anything useful, and might even cause damage to the USB device that was plugged into it.

An actual USB to Ethernet adapter would be much more complicated. Its exact design would depend on what types of USB devices it needed to work with, and what it was supposed to do with them. (What do you expect to happen when you plug a keyboard, a camera, or a hard disk into a network, after all? There's no obvious single way for this to work.)