A driver is a software program that allows a computer to communicate with a hardware device, in this case, the LEICA TC 407 total station. The driver acts as a translator between the computer's operating system and the device, enabling the computer to send and receive data to and from the device.
Some late-production TC 407 models had a proprietary Leica USB port (GDU – GeoCOM Data Upload). For those, you need the from the 2006 “Leica System 500 CD.” This is extremely hard to find, so most users stick with the RS-232 route. LEICA TC 407 driver