TRH Central (online version) is for TJ-USB, RH-USB, IR-USB, and UTC-USB products. 
A software CD is provided with your product which includes the TRH Central (Offline version) software. 
The offline version includes Microsoft .NET Framework 3.5 which makes the install package very large (190 MB).
You can either install the offline version from your software CD or download & install the online version from the web site. 
If your PC does not have .NET Framework 3.5, the online version will guide you to download the .NET Framework 3.5 from Microsoft.
