It counts both steering and steps when you move the wheel. Other models use a plastic slot wheel and an optical slot sensor as well as an LED for encoders and decoders infrared.
A part of the optical wheel to which it is attached is housed in a U-shaped plastic housing and uses a rotary switch. The optical wheel is part of the scroll wheel in the upper middle of the screen. When you scroll down the page, the page or anything that can be scrolled up goes up a few pixels and it can be very annoying. It appears on PCs and laptops and is not exclusive to a particular version of the Windows operating system.
