There was a time when if you bought a USB mouse ... when you bought a mouse with a PS/2 connector fitted, it may well have come with an adapter for a 9-pin RS232 serial port.

As Microsoft's Raymond Chen recently explained, PS/2 and USB are completely different protocols that are not compatible in any way. The adapter simply connected one set of pins to another ...

It connected one set of pins to another, but it contained no circuitry. All of the smarts was in the mouse. "The mouse detected whether it received USB-like signals or PS/2-like signals on the ...