I use this one Amazon - USB-RS232 FTDI-Chipset compatible with Windows 7 64 bit with appropriate cable it works with 500 series, 800 series, Legacy and SpeakerLink DSPs.

Regards,
Carl

Update: Works fine with Windows 10.

861v6+ID40, HD621, 8000.2, 7200HC, 7200.2, SKYQ Silver, PS3, PDP-LX6090, QNAP TS870-Pro (8*6TB), Roon, iPadAir2.
[In Reserve] C15, MD600 (2*3TB), TwinStore RM (2*2TB)