... module of USB<->RS232, USB <-> RS485, USB<->LINK (Smartgen special). 1, RXD LED: When PC(personal computer) receives data, ... When PC sends out data, this light will flash.3, POWER LED: When the SG72 module successfully connect to USB, ... 4, USB interface: Connect SG72 module to the USB interface on PC by the data line from smartgen.5, LINK ... is a generic DB9 serial communication interface. sg72 module