USB Installation ( Silicon Labs USB to RJ11 )
Before plugging the USB device into your windows based computer check the supplied software for the USB Driver.
Navigate to USB Driver folder on the memory stick and right click slabvcp.inf and select Install.
Double click either file depending on your operating system
CP210xVCPInstaller_x64.exe ( 64bit Windows )
CP210xVCPInstaller_x86.exe ( 32bit Windows )
Wait for installation to finish before plugging USB to Serial device in.
A restart may be needed.