The USB485B converts the short range USB output of the computer into the industry standard, long range RS485 protocol. It is used to communicate between the PC and LOR light controllers. Only one USB485B is required to operate an entire network of LOR controllers. The USB485B has a built in voltage booster that provides power for LOR accessories such as the RF-V4 wireless unit. If you are going to connect a wireless unit directly to a PC or if you plan on future interactive displays you should choose the USB485B.