A: Newer Leica instruments use a 5-pin LEMO connector and different voltage levels (RS-422 vs RS-232). The TC 407 requires true RS-232 at ±12V. Some modern cables are TTL (0-3.3V) and will not work.
Many cheap eBay/Amazon cables use counterfeit Prolific chips. Windows may show “Code 10” error. If that happens, buy an FTDI-based cable such as the TRENDnet TU-S9 or StarTech ICUSB232FTN . LEICA TC 407 driver
before plugging the cable into the PC.