LEX stands for Local Extender and REX stands for Remote Extender. These two units comprise a standard Icron Extension solution. The LEX unit interfaces to the Host PC via a Type-B USB connector or a built-in Type-A USB cable. The LEX interfaces to the REX unit over the extension media (Cat 5e UTP, Fibre, etc.) and the REX unit provides connectivity for one or more USB devices at the remote location.